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Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: nacnud on 10/26/2017 07:14 PM

Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: nacnud on 10/26/2017 07:14 PM
First Object From Another Star System Found Near Earth,

https://www.youtube.com/watch?v=0GPqb-bXhjg
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: whitelancer64 on 10/26/2017 07:28 PM
Pretty good article here:

http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/26/2017 07:37 PM
Here’s the official press release.

Small Asteroid or Comet 'Visits' from Beyond the Solar System

Quote
A small, recently discovered asteroid - or perhaps a comet - appears to have originated from outside the solar system, coming from somewhere else in our galaxy. If so, it would be the first "interstellar object" to be observed and confirmed by astronomers.
This unusual object - for now designated A/2017 U1 - is less than a quarter-mile (400 meters) in diameter and is moving remarkably fast. Astronomers are urgently working to point telescopes around the world and in space at this notable object. Once these data are obtained and analyzed, astronomers may know more about the origin and possibly the composition of the object.
A/2017 U1 was discovered Oct. 19 by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala during the course of its nightly search for Near-Earth Objects for NASA. Rob Weryk, a postdoctoral researcher at the University of Hawaii Institute for Astronomy (IfA), was first to identify the moving object and submit it to the Minor Planet Center. Weryk subsequently searched the Pan-STARRS image archive and found it was present in images taken the previous night, but was not initially identified by the moving object processing.
Weryk immediately realized this was an unusual object. "Its motion could not be explained using either a normal solar system asteroid or comet orbit," he said. Weryk contacted IfA graduate Marco Micheli, who had the same realization using his own follow-up images taken at the European Space Agency's telescope on Tenerife in the Canary Islands. But with the combined data, everything made sense. Said Weryk, "This object came from outside our solar system."
"This is the most extreme orbit I have ever seen," said Davide Farnocchia, a scientist at NASA's Center for Near-Earth Object Studies (CNEOS) at the agency's Jet Propulsion Laboratory in Pasadena, California. "It is going extremely fast and on such a trajectory that we can say with confidence that this object is on its way out of the solar system and not coming back."
The CNEOS team plotted the object's current trajectory and even looked into its future. A/2017 U1 came from the direction of the constellation Lyra, cruising through interstellar space at a brisk clip of 15.8 miles (25.5 kilometers) per second.
The object approached our solar system from almost directly "above" the ecliptic, the plane in space near where the planets and most asteroids orbit the Sun, so it did not have any close encounters with the eight major planets during its plunge toward the Sun. On Sept. 2, the small body crossed under the ecliptic just inside of Mercury's orbit and then made its closest approach to the Sun on Sept. 9. Pulled by the Sun's gravity, the object made a hairpin turn under our solar system, passing below Earth's orbit on Oct. 14 at a distance of about 15 million miles (24 million kilometers) -- about 60 times the distance to the Moon. It has now shot back up above the plane of the planets and, travelling at 27 miles per second (44 kilometers per second) with respect to the Sun, the object is speeding toward the constellation Pegasus.
"We have long suspected that these objects should exist, because during the process of planet formation a lot of material should be ejected from planetary systems. What's most surprising is that we've never seen interstellar objects pass through before," said Karen Meech, an astronomer at the IfA specializing in small bodies and their connection to solar system formation.
The small body has been assigned the temporary designation A/2017 U1 by the Minor Planet Center (MPC) in Cambridge, Massachusetts, where all observations on small bodies in our solar system -- and now those just passing through -- are collected. Said MPC Director Matt Holman, "This kind of discovery demonstrates the great scientific value of continual wide-field surveys of the sky, coupled with intensive follow-up observations, to find things we wouldn't otherwise know are there."
Since this is the first object of its type ever discovered, rules for naming this type of object will need to be established by the International Astronomical Union.
"We have been waiting for this day for decades," said CNEOS Manager Paul Chodas. "It's long been theorized that such objects exist - asteroids or comets moving around between the stars and occasionally passing through our solar system - but this is the first such detection. So far, everything indicates this is likely an interstellar object, but more data would help to confirm it."
Animation of path of A2017U1

http://www.ifa.hawaii.edu/info/press-releases/interstellar/

NASA Press Release

https://www.nasa.gov/feature/jpl/small-asteroid-or-comet-visits-from-beyond-the-solar-system
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: zubenelgenubi on 10/26/2017 08:00 PM
Pretty good article here:

http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/
Quote
What gave this object away as an interstellar visitor wasn't its very high inclination (122°) with respect to Earth's orbit, which isn't particularly rare, but more critically its extremely hyperbolic eccentricity (1.19).
<snip>
More intriguing is the fact that A/2017 U1 is coming from a spot only 6° from the solar apex, the direction that our Sun is moving (at about 20 km/s) through its interstellar neighborhood and thus, statistically, the most likely incoming direction for an interstellar visitor.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Orbiter on 10/26/2017 08:04 PM
First time a comet has been re-designated as an asteroid, too. Almost 100% certainly an interstellar object, in this case an asteroid that came from another solar system. Absolutely incredible!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/26/2017 08:22 PM
How precisely will they be able to pin down where it came from and where it’s going?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Orbiter on 10/26/2017 08:25 PM
How precisely will they be able to pin down where it came from and where it’s going?

Its location of origin in the night sky was close to the star Vega, however that does not mean that it came from the Vega system. It could have come from any of the billions of stars in the Milky Way Galaxy.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 10/26/2017 08:26 PM
Here's the latest MPECs:
http://www.minorplanetcenter.net/mpec/K17/K17UI3.html (http://www.minorplanetcenter.net/mpec/K17/K17UI3.html)
http://www.minorplanetcenter.net/mpec/K17/K17UI5.html (http://www.minorplanetcenter.net/mpec/K17/K17UI5.html)

Not that many observations, but strongly hyperbolic.  However, some caution is needed; I'm waiting until next week before being sure it's interstellar.

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/26/2017 08:27 PM
How precisely will they be able to pin down where it came from and where it’s going?

Its location of origin in the night sky was close to the star Vega, however that does not mean that it came from the Vega system. It could have come from any of the billions of stars in the Milky Way Galaxy.

Thanks. Was it travelling too fast to be captured by the Sun?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/26/2017 09:04 PM
Thanks. Was it travelling too fast to be captured by the Sun?
The Sun alone doesn't capture anything. Ignoring non-gravitational forces (which should be minor in most realistic scenarios) anything arriving from interstellar space will depart at the same speed. Capture requires interactions with additional bodies.

In this case, estimates I've seen put the hyperbolic excess over 20 km/s (but take that with a grain of salt, uncertainties may be large), and it doesn't come anywhere near any of the giant planets, so it's definitely too fast to capture. It's also likely too fast for an solar system Oort cloud object perturbed by something like Planet 9 or a plausible recent stellar encounter.

Edit:
Lee Billings has a nice writeup on sciam
https://www.scientificamerican.com/article/astronomers-spot-first-ever-space-rock-from-another-star/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Zed_Noir on 10/27/2017 05:22 AM
:) Not too seriously.

The object's trajectory in and out of the Solar system follows the flight path of a  covert system survey mission as describe in some of the more esoteric Sci-Fi literature.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 10/27/2017 08:50 AM
In this case, estimates I've seen put the hyperbolic excess over 20 km/s (but take that with a grain of salt, uncertainties may be large), and it doesn't come anywhere near any of the giant planets, so it's definitely too fast to capture. It's also likely too fast for an solar system Oort cloud object perturbed by something like Planet 9 or a plausible recent stellar encounter.

Latest analysis of the trajectory I've seen is https://projectpluto.com/temp/2017u1.htm (https://projectpluto.com/temp/2017u1.htm)

Incoming & outgoing Vinf ~= 26km/s

Starting to see some (low res) spectra appearing as well ...

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 10/27/2017 10:43 AM
The fact that PANSTARRS A2017/U1 appears not to have developed any kind of coma is interesting. Even if it is non-cometary in form, you would have expected there to have been at least some volatiles that would have activated during its journey through the inner solar system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 10/27/2017 10:58 AM
The fact that PANSTARRS A2017/U1 appears not to have developed any kind of coma is interesting. Even if it is non-cometary in form, you would have expected there to have been at least some volatiles that would have activated during its journey through the inner solar system.

Why? For example, I don't think you'd expect volatiles from a body ejected from inside the ice-line (e.g. by a Jupiter-analogue during a "grand tack" equivalent or inward migration to form a hot-Jupiter).

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: TakeOff on 10/27/2017 02:10 PM
It might've lost its volatiles billions of years ago before it was ejected from its (now long gone) binary star system of origin.

jebbo:
I think the point is that Jupiter couldn't have done it (alone) because they never get close.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/27/2017 04:12 PM
Why? For example, I don't think you'd expect volatiles from a body ejected from inside the ice-line (e.g. by a Jupiter-analogue during a "grand tack" equivalent or inward migration to form a hot-Jupiter).
Agreed, the existence of volatile free interstellar asteroids does not seem at all surprising. We know a lot of rocky stuff must have been ejected by Jupiter over the history of the solar system.

OTOH, the general expectation seems to have been that we would see interstellar comets before asteroids,  because they are easier to detect, and models of our own solar system predict more icy bodies being ejected. So the fact that the first one was an asteroid may be telling us something... or it might just be a fluke ;)

A recent (but pre A/2017 U1 obviously) paper:
An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets (https://arxiv.org/abs/1702.02237) Toni Engelhardt, Robert Jedicke, Peter Veres, Alan Fitzsimmons, Larry Denneau, Ed Beshore, Bonnie Meinke (accepted for publication in AJ)
Quote
We derived 90% confidence limits (CL) on the interstellar number density (ρCLIS) of interstellar objects (ISO; comets and asteroids) as a function of the slope of their size-frequency distribution and limiting absolute magnitude. To account for gravitational focusing, we first generated a quasi-realistic ISO population to ~750 au from the Sun and propagated it forward in time to generate a steady state population of ISOs with heliocentric distance <50 au. We then simulated the detection of the synthetic ISOs using pointing data for each image and average detection efficiencies for each of three contemporary solar system surveys --- PS1, the Mt. Lemmon Survey, and the Catalina Sky Survey. These simulations allowed us to determine the surveys' combined ISO detection efficiency under several different but realistic modes of identifying ISOs in the survey data. Some of the synthetic detected ISOs had eccentricities as small as 1.01 --- in the range of the largest eccentricities of several known comets. Our best CL of ρCLIS=1.4×10−4 au−3 implies that the expectation that extra-solar systems form like our solar system, eject planetesimals in the same way, and then distribute them throughout the galaxy, is too simplistic, or that the SFD or behavior of ISOs as they pass through our solar system is far from expectations.

Fitzsimmons (co-author on the above) has taken spectra of A/2017 U1
https://twitter.com/FitzsimmonsAlan/status/923928561722982400
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 10/27/2017 04:20 PM
Agreed, the existence of volatile free interstellar asteroids does not seem at all surprising. We know a lot of rocky stuff must have been ejected by Jupiter over the history of the solar system.

OTOH, it the general expectation seems to have been that we would see interstellar comets before asteroids,  because they are easier to detect, and models of our own solar system predict more icy bodies being ejected. So  the fact that the first one was an asteroid may be telling us something... or it might just be a fluke ;)

True. I'm wondering what the LSST yield of similar objects will be!

Quote
A recent (but pre A/2017 U1 obviously) paper:
An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets (https://arxiv.org/abs/1702.02237) Toni Engelhardt, Robert Jedicke, Peter Veres, Alan Fitzsimmons, Larry Denneau, Ed Beshore, Bonnie Meinke (accepted for publication in AJ)

Thanks! Hasn't seen that one. Too many papers, not enough time :)

Quote
Fitzsimmons (co-author on the above) has taken spectra of A/2017 U1
https://twitter.com/FitzsimmonsAlan/status/923928561722982400
G
Saw that ... was struck by it being red. Makes me wonder about organics (tholins) ...

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 10/27/2017 04:30 PM
Oh, and lots of people having fun calling it "Rama" ... sadly a rendezvous isn't particularly feasible

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/27/2017 07:23 PM
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isn’t there an idea that one way of exploring other star systems is to embed technology into things like asteroids?

Quote
… still, I can’t help but wonder. I put absolutely no weight on this speculation, and would even bet heavily against it, but it’s an obvious thought and I feel I have to at least mention it.

Space is vast. Even in our solar system, the outer planets are billions of kilometers away, with smaller icy objects extending for a trillion or two past that. No doubt, there is debris from other stars passing us at all kinds of distances. Most would never get within a light year, 10 trillion km.

From that distance, the inner solar system is a ridiculously small target. Mercury’s orbit is only about 115 million km across. For something coming from interstellar space, getting that close to the Sun is threading the eye of a very, very narrow needle.

Yet A/2017 U1 did just that. It passed the Sun at a distance of about 45 million kilometers. That’s… weird.

Part of this is what we call a selection effect: An object like this passing out by the orbit of Jupiter would be very faint, so it’s harder to discover. We only see the ones that happen to pass close to Earth. So even before this, I would’ve wagered the first one we discover would be passing through the inner solar system as opposed to farther out.

But still, getting that close to the Sun seems unusual.

Let me be clear: I am NOT saying this is an alien spaceship. But if I were an alien race interested in exploring other systems, this is pretty much the sort of path I’d put my probe on. I’d aim it to pass deep within the alien solar system, check out the habitable planets, and use the star’s gravity to bend the orbit to aim it at the next target.

Again, I’m quite sure this is a natural object and not an alien spaceship. Even so, it’s certainly not a mundane one: It’s a freaking asteroid ejected from another star that’s been wandering the galaxy for eons and passed a few million kilometers from the Sun and Earth and is on its way back out into the void!

http://www.syfy.com/syfywire/breaking-have-astronomers-discovered-our-first-interstellar-visitor-note-not-aliens
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/27/2017 07:42 PM
Quote
Alan Fitzsimmons
@FitzsimmonsAlan
Spectrum of A/2017 U1 obtained on Wednesday night with the @INGLaPalma 4.2m WHT. Colour is red like Kuiper Belt Objects, featureless.

https://mobile.twitter.com/FitzsimmonsAlan/status/923928561722982400
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 10/27/2017 09:25 PM
I guess it's a Vulcan survey ship then, come to check out our progress with EM drives.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: whitelancer64 on 10/27/2017 10:11 PM
Makes me wonder, what would a rocky/metallic object, ~1/4 mile in diameter, entering Earth's atmosphere at 56,000+ mph look like?

6 km diameter crater, extensive local devastation and widespread regional damage.

http://www.purdue.edu/impactearth/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bob Shaw on 10/27/2017 10:36 PM
Rama!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/27/2017 10:40 PM
Makes me wonder, what would a rocky/metallic object, ~1/4 mile in diameter, entering Earth's atmosphere at 56,000+ mph look like?

6 km diameter crater, extensive local devastation and widespread regional damage.

http://www.purdue.edu/impactearth/
FWIW per JPL (https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=A/2017%20U1;old=0;orb=1;cov=0;log=0;cad=1#orb) the objects speed relative to Earth at closest approach was ~60 km/s (~134,000 mph) . Definitely gonna leave a mark ;)

The 25 km/s mentioned elsewhere is the speed relative to the Sun before entering / after leaving the solar system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bob Shaw on 10/27/2017 10:40 PM
On a more serious note, could this object be chased and surveyed in any reasonable timescale/technology?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: QuantumG on 10/27/2017 10:44 PM
I guess it's a Vulcan survey ship then, come to check out our progress with EM drives.

Or it's Karellen.


:(

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/27/2017 11:00 PM
On a more serious note, could this object be chased and surveyed in any reasonable timescale/technology?
No realistically. We only spotted it after it passed Earth on the way out, and it's significantly faster than anything we've launched (Vinf ~25 km/s vs Voyager 1 at around ~16 km/s  ). Even if we built something faster, the time required to build it would give the asteroid a huge head start.

However, the fact Pan-STARRS found this one suggests that LSST will have a decent chance of finding more. Catching one on the inbound leg would allow a lot more study, perhaps even a flyby mission for a larger cometary object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: notsorandom on 10/28/2017 12:04 AM
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isn’t there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bob Shaw on 10/28/2017 12:41 AM
On a more serious note, could this object be chased and surveyed in any reasonable timescale/technology?
No realistically. We only spotted it after it passed Earth on the way out, and it's significantly faster than anything we've launched (Vinf ~25 km/s vs Voyager 1 at around ~16 km/s  ). Even if we built something faster, the time required to build it would give the asteroid a huge head start.

However, the fact Pan-STARRS found this one suggests that LSST will have a decent chance of finding more. Catching one on the inbound leg would allow a lot more study, perhaps even a flyby mission for a larger cometary object.

Imagine seeing a part of another star system!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 10/28/2017 01:08 AM
It's Zor's battlefortress, and it's just missed us

(https://img.purch.com/h/1400/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA3MS8yNjEvb3JpZ2luYWwvaW50ZXJzdGVsbGFyLWNvbWV0LWFzdGVyb2lkLWEyMDE3LXUxLmdpZj8xNTA5MTE2MzAy)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/28/2017 02:20 AM
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.
Agreed. It's moving fairly fast by our standards, but it's really slow for interstellar missions. Interestingly 25 km/s is also right in the middle of range the Engelhardt paper I linked earlier predicted for natural objects.

Of course one can imagine scenarios where an artificial object could be that slow, but IMO it makes arguments that the trajectory is "what a spaceship would do" a lot less compelling.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: the_other_Doug on 10/28/2017 03:22 AM
My first thought, when I heard about this, was "Wow -- that would make one heck of a flash if it impacted even a small Solar System body -- and the extrasolar body was made of anti-matter."

I know it's extremely unlikely.  But boy, what a flash that would make, eh?  It would also prove without a shadow of a doubt that the body was extra-solar... :)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: plutogno on 10/28/2017 05:20 AM
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/28/2017 08:39 AM
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isn’t there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Not sure that all applies if it was machine intelligence.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 10/28/2017 08:58 AM
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus

That's not how anti-matter works.  Anti-matter has positive mass just like regular matter.  You can't tell matter from anti-matter based on gravitational interactions of any sort.

However, if this object were somehow anti-matter, the charged particles of the solar wind hitting it would annihilate themselves and the anti-matter they hit, releasing enormous amounts of energy.  So there's no chance we would miss the fact that it was anti-matter.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 10/28/2017 09:01 AM
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isn’t there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Not sure that all applies if it was machine intelligence.

Why not?  It seems to me the point is valid whether it's machine intelligence or not.  If machine intelligence sent this probe, that machine intelligence is either extremely long lived or long gone, unless the object slowed down right before it got here.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/28/2017 09:21 AM
Phil Plait does make an interesting point that if you were an alien race this is exactly where you would aim something to check out our solar system without alarming any local species. Isn’t there an idea that one way of exploring other star systems is to embed technology into things like asteroids?
Any alien that might have sent this thing is either extremely long lived or long gone. It's moving fast but still took a long time to get here. That or it really slowed down right before it got here.

Not sure that all applies if it was machine intelligence.

Why not?  It seems to me the point is valid whether it's machine intelligence or not.  If machine intelligence sent this probe, that machine intelligence is either extremely long lived or long gone, unless the object slowed down right before it got here.

That was my point that machine intelligence is more likely to exist on long time scales compared to biological life.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 10/28/2017 10:22 AM
How rare is this object really? Is it a 1 in a century sort of thing or have plenty of others probably passed by and we just didn't spot them?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: LouScheffer on 10/28/2017 02:58 PM
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus
However, if this object were somehow anti-matter, the charged particles of the solar wind hitting it would annihilate themselves and the anti-matter they hit, releasing enormous amounts of energy.  So there's no chance we would miss the fact that it was anti-matter.

This is not clear - space is pretty sparse.  According to Wikipedia, interplanetary space has about 5-10 protons per cubic cm.  That's 10^7 protons per cubic meter.  According to JPL, the speed relative to the sun is about 60 km/sec, so each m^2 of surface sweeps up 10^7 x 6x10^4 = 6x10^11 protons.  Divide by Avagadro's number (6x10^23) to get 10^-12 grams/sec or 10^-15 kg/sec/m^2.  Now you need to multiply by 2*c^2 to get energy.  That's about 2*10^17, so it's releasing about 200 w/m^2, in assorted charged particles and gamma rays.  About 1/2 will head away from the object, and half into it and get absorbed.  So it's getting about 100 w/m^2 of extra heating.   But it's already absorbing most of the sunlight that hits it (estimated 92%) from 1300 w/m^2.  So it adds only a few percent to the heating.

Could we see the gamma rays?   We have at most 100W of gamma rays, so about 100/(1.6 x 10^-19 J/ev * 0.6 Mev) = 10^15 gamma rays per second.   If we are 10^10 meters away (much less than one AU) these are spread over an area of 4 x pi x 10^20 or about 10^21 m^2.  So at most 10^-6 gamma rays per square meter per second.  A gamma ray detecting satellite of 10 m^2 would see one per day.  No way we could see that either.

So it could be made of antimatter, without obvious consequences.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mark K on 10/28/2017 03:30 PM

So it could be made of antimatter, without obvious consequences.

You skipped dust. Dust flux in inner solar system would conservativly mean 100s of partcles of mass around 10^-16 kgs or more hitting per second (flux would be much higher for nanodust many orders of magnitude more.) I think we oould detect the sparkling.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 10/28/2017 03:54 PM
I assume that we should have a good idea of this object's trajectory, if not yet, then surely after it has been tracked for a while longer. Is anybody calculating its trajectory backwards, comparing its location in the past with the calculated location of nearly stars at the same time?

With Gaia, we should certainly be able to backtrack the paths of nearby stars to considerable accuracy for many millions of years in the past, so the main source of uncertainty in my opinion might be the exact trajectory of the object itself. Obviously there would be some degree of uncertainty, increasing the further back in time you look, but if we find that the object was within say 0.01 pc of some red dwarf star five million years ago, with an uncertainty of 0.02 pc, that should significantly increase out understanding of the object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: zubenelgenubi on 10/28/2017 04:33 PM
How rare is this object really? Is it a 1 in a century sort of thing or have plenty of others probably passed by and we just didn't spot them?

The consensus among astronomers: the discovery of a minor body on an "extreme" hyperbolic trajectory is a type that we've been waiting for, for a long time:
1) a new comet is discovered,
2) observations are integrated into preliminary orbital elements,
3) what does e = ? (e is eccentricity)

Someone would have to do a literature search to find the earliest printed mentions of the realization that finding a body on an hyperbolic solar orbit, with e = significantly greater than 1.000 means it's an extra-solar interloper.  I wonder if Newton or Halley or Herschel (William or Catherine or John) had such a realization.

I also think that the astronomical consensus is that our solar system is penetrated by small interstellar wanderers all the time.  It's only now, with deep-magnitude, large-scale or all-sky frequent surveys, and the computer hardware and software to search lots and lots of data to correlate moving bodies, that we are rewarded with such a discovery.

Again, a literature search might turn up a paper with the math determining the frequency of "penetration" of a given solar-centered volume, given an assumed flux of minor bodies.
***

I assume that we should have a good idea of this object's trajectory, if not yet, then surely after it has been tracked for a while longer. Is anybody calculating its trajectory backwards, comparing its location in the past with the calculated location of nearly stars at the same time?

<snip>

Re-quoting my post up-thread--there's significance to the fact that the object came from the direction near to the solar apex.

We may not deduce a progenitor system, only that our Solar System sort-of "ran over" A/2017 U1 as our Sun goes on its 250 million year orbit around/within our Galaxy.
 
Pretty good article here:

http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/
Quote
What gave this object away as an interstellar visitor wasn't its very high inclination (122°) with respect to Earth's orbit, which isn't particularly rare, but more critically its extremely hyperbolic eccentricity (1.19).
<snip>
More intriguing is the fact that A/2017 U1 is coming from a spot only 6° from the solar apex, the direction that our Sun is moving (at about 20 km/s) through its interstellar neighborhood and thus, statistically, the most likely incoming direction for an interstellar visitor.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 10/28/2017 05:07 PM
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus
However, if this object were somehow anti-matter, the charged particles of the solar wind hitting it would annihilate themselves and the anti-matter they hit, releasing enormous amounts of energy.  So there's no chance we would miss the fact that it was anti-matter.

This is not clear - space is pretty sparse.  According to Wikipedia, interplanetary space has about 5-10 protons per cubic cm.  That's 10^7 protons per cubic meter.  According to JPL, the speed relative to the sun is about 60 km/sec, so each m^2 of surface sweeps up 10^7 x 6x10^4 = 6x10^11 protons.  Divide by Avagadro's number (6x10^23) to get 10^-12 grams/sec or 10^-15 kg/sec/m^2.  Now you need to multiply by 2*c^2 to get energy.  That's about 2*10^17, so it's releasing about 200 w/m^2, in assorted charged particles and gamma rays.  About 1/2 will head away from the object, and half into it and get absorbed.  So it's getting about 100 w/m^2 of extra heating.   But it's already absorbing most of the sunlight that hits it (estimated 92%) from 1300 w/m^2.  So it adds only a few percent to the heating.

Could we see the gamma rays?   We have at most 100W of gamma rays, so about 100/(1.6 x 10^-19 J/ev * 0.6 Mev) = 10^15 gamma rays per second.   If we are 10^10 meters away (much less than one AU) these are spread over an area of 4 x pi x 10^20 or about 10^21 m^2.  So at most 10^-6 gamma rays per square meter per second.  A gamma ray detecting satellite of 10 m^2 would see one per day.  No way we could see that either.

So it could be made of antimatter, without obvious consequences.

Thanks for doing the calculation!  The numbers are less than I thought they would be.

However, I think you're underestimating things somewhat.  You're calculating the number of protons hitting the object based on the object's relative speed of 60 km/s.  But the solar wind itself has a speed of 400 km/s.  You the number of proton hits per second is around an order of magnitude greater than your estimate.  So instead of 100 W/m^2, it's getting more like 700 W/m^2.

https://solarscience.msfc.nasa.gov/SolarWind.shtml
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/28/2017 07:23 PM
Again, a literature search might turn up a paper with the math determining the frequency of "penetration" of a given solar-centered volume, given an assumed flux of minor bodies.
The Engelhardt paper I linked earlier (http://forum.nasaspaceflight.com/index.php?topic=44075.msg1742703#msg1742703) does exactly that, and has references to earlier work.

Another related paper Realistic Detectability of Close Interstellar Comets (https://arxiv.org/abs/1607.08162) Nathaniel V. Cook, Darin Ragozzine, Mikael Granvik, Denise C. Stephens

As you say, this has been an active area of research / speculation for a long time.

My non-professional impressions
* Spotting this one isn't a huge surprise. We know there has to be a lot of stuff ejected from other solar systems.
* The uncertainties on estimates to date are very large, some models suggested we should have seen interstellar comets already, others predicted that LSST has little chance of finding any.
* The fact that this one was an asteroid rather than a comet is somewhat surprising. Both are expected to exist, but comets are easier to detect and generally expected to be more common.

Quote
We may not deduce a progenitor system, only that our Solar System sort-of "ran over" A/2017 U1 as our Sun goes on its 250 million year orbit around/within our Galaxy.
Eric Mamajek (who has done a lot of work on nearby stars) wrote a series of tweets on this

https://twitter.com/EricMamajek/status/924061457280507904
Quote
1/n #A2017U1 interstellar asteroid: object came from RA,Dec=281.09,+34.59 deg; est. "inbound" Galactic velocity U,V,W =-11.0,-22.4,-7.3 km/s

2/n #A2017U1 interstellar asteroid: velocity doesn't match any nearby individ stars -doesn't belong to Oort cloud of nearby stars (<12 ly)

3/n #A2017U1: However, velocity is w/i ~5km/s of median velocity of stars within 25pc, i.e. vel completely typical for interstellar "stuff"

4/n #A2017U1 NO evidence it came from Vega -entrd sol sys frm that dirctn, but Vega nowhre near it thsnds of yrs ago


Bill Gray also wrote a nice general FAQ on this object
https://projectpluto.com/temp/2017u1.htm
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: LouScheffer on 10/28/2017 07:42 PM

So it could be made of antimatter, without obvious consequences.

You skipped dust. Dust flux in inner solar system would conservativly mean 100s of partcles of mass around 10^-16 kgs or more hitting per second (flux would be much higher for nanodust many orders of magnitude more.) I think we oould detect the sparkling.

From the paper Interplanetary Dust (http://adsbit.harvard.edu//full/1990pihl.book..207L/0000208.000.html), the mass density of dust is comparable to that of the solar wind.  Also, the reaction may be less efficient -  the first edge of a dust particle may hit and the reaction might blow the rest of the particle away before it can annihilate.   And even several times the solar wind number would be hard to detect, especially since the object's intrinsic albedo is unknown.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: zubenelgenubi on 10/29/2017 12:08 AM
Again, a literature search might turn up a paper with the math determining the frequency of "penetration" of a given solar-centered volume, given an assumed flux of minor bodies.
The Engelhardt paper I linked earlier (http://forum.nasaspaceflight.com/index.php?topic=44075.msg1742703#msg1742703) does exactly that, and has references to earlier work.
<snip>

Thanks, hop.  I should have started my "literature search" up-thread at your earlier posting!  :)

Thank you also for the other links and your impressions in this most recent posting.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 10/29/2017 12:29 AM
and the extrasolar body was made of anti-matter."

if the object was made of anti-matter it would have followed the other branch of the hyperbola, the one without the Sun at its focus
However, if this object were somehow anti-matter, the charged particles of the solar wind hitting it would annihilate themselves and the anti-matter they hit, releasing enormous amounts of energy.  So there's no chance we would miss the fact that it was anti-matter.

This is not clear - space is pretty sparse.  According to Wikipedia, interplanetary space has about 5-10 protons per cubic cm.  That's 10^7 protons per cubic meter.  According to JPL, the speed relative to the sun is about 60 km/sec, so each m^2 of surface sweeps up 10^7 x 6x10^4 = 6x10^11 protons.  Divide by Avagadro's number (6x10^23) to get 10^-12 grams/sec or 10^-15 kg/sec/m^2.  Now you need to multiply by 2*c^2 to get energy.  That's about 2*10^17, so it's releasing about 200 w/m^2, in assorted charged particles and gamma rays.  About 1/2 will head away from the object, and half into it and get absorbed.  So it's getting about 100 w/m^2 of extra heating.   But it's already absorbing most of the sunlight that hits it (estimated 92%) from 1300 w/m^2.  So it adds only a few percent to the heating.

Could we see the gamma rays?   We have at most 100W of gamma rays, so about 100/(1.6 x 10^-19 J/ev * 0.6 Mev) = 10^15 gamma rays per second.   If we are 10^10 meters away (much less than one AU) these are spread over an area of 4 x pi x 10^20 or about 10^21 m^2.  So at most 10^-6 gamma rays per square meter per second.  A gamma ray detecting satellite of 10 m^2 would see one per day.  No way we could see that either.

So it could be made of antimatter, without obvious consequences.

Thanks for doing the calculation!  The numbers are less than I thought they would be.

However, I think you're underestimating things somewhat.  You're calculating the number of protons hitting the object based on the object's relative speed of 60 km/s.  But the solar wind itself has a speed of 400 km/s.  You the number of proton hits per second is around an order of magnitude greater than your estimate.  So instead of 100 W/m^2, it's getting more like 700 W/m^2.

https://solarscience.msfc.nasa.gov/SolarWind.shtml


I'm sure you'd see a whole lot of 0.5 MeV gamma rays spewing off the thing, it'd be pretty obvious something was fishy.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 10/29/2017 01:13 AM
Is there any spectroscopic analysis of this object?

Maybe it came from a collision in our solar system that sent it onto a crazy orbital trajectory that it's just now returning from.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 10/29/2017 01:18 AM
You can't get a hyperbolic trajectory from a collision and have the hyperbolic fragments return.

Hyperbolic = Escape velocity or more
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: zubenelgenubi on 10/29/2017 01:32 AM
Is there any spectroscopic analysis of this object?

Up-thread:
Quote
Alan Fitzsimmons
@FitzsimmonsAlan
Spectrum of A/2017 U1 obtained on Wednesday night with the @INGLaPalma 4.2m WHT. Colour is red like Kuiper Belt Objects, featureless.

https://mobile.twitter.com/FitzsimmonsAlan/status/923928561722982400

Mike Brown @plutokiller responded in two separate replies that it's "kind of normal-KBO-red type color" and then "a little redder than even the reddest trojans."

I wonder if the extreme color is a result of a greater exposure to stellar ultraviolet than the Sun?  That is, was the parent star an "earlier" spectral class than the Sun?  Hotter, therefore producing more ultraviolet flux, therefore photochemical reactions progress at a faster rate?

Or, have the slow chemical reactions producing tholins or such had longer than the age of our Solar System to progress?  (Do those reactions continue in the dark and cold of interstellar space?)  Is A/2017 U1 older than our Solar System, because it was formed around another star older than the Sun?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 10/29/2017 05:03 AM
You can't get a hyperbolic trajectory from a collision and have the hyperbolic fragments return.

Hyperbolic = Escape velocity or more

What if it was from more than one collision?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: as58 on 10/29/2017 05:39 AM
You can't get a hyperbolic trajectory from a collision and have the hyperbolic fragments return.

Hyperbolic = Escape velocity or more

What if it was from more than one collision?

A collision, or more likely gravitational scattering without actually colliding, in the outer Solar System could send an object on a hyperbolic trajectory. However, getting as large v_inf as this object has by gravitational scattering of a bound Solar System object seems very unlikely to me.

edit: as explained in Bill Gray's FAQ that hop linked to, the thing that makes people confident that A/2017 U1 really is an interstellar object is that that the eccentricity is significantly greater than one. On the other hand, if the eccentricity were something like 1.005, it would probably be a Solar System object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/29/2017 05:39 AM
What if it was from more than one collision?
A collision in the far outer solar system could send something inward on a slightly hyperbolic trajectory, but this thing has a hyperbolic excess of ~25 km/s. Getting that from a collision in the outer solar system seems like a tall order.

edit:
Bill Gray's FAQ addresses this, suggestion #4
https://projectpluto.com/temp/2017u1.htm#alt_ideas

Quote
The fourth suggestion was that two objects collided, and a bit flew off at really high speed, and that's what we're seeing. Aside from the problems in getting two objects to hit that hard, these are not rubber balls; when rocks or ice chunks hit, you get rubble not moving much faster or slower than the incoming objects. You don't have some bits coming out at interstellar speeds.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 10/29/2017 05:55 AM
Very interesting find. Too bad we don't have a spaceprobe ready (and a drive to match) to go catch it and investigate it... But next time one of these comes around, we might be ready.

Regarding orgins, there is a simple short-hand to estimate travel distances: for each km/s at infinity, the object will travel about a parsec per million years. So for this one, 25 parsecs (~82 light years) per million year. Even if it travelled only a few million years, it could have come from very far away!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 10/29/2017 08:01 AM
How old could this thing plausibly be?
eg what is the average and the extreme 1% of the expected age distribution?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: LouScheffer on 10/29/2017 11:13 AM
How old could this thing plausibly be?
eg what is the average and the extreme 1% of the expected age distribution?
Using the estimate above, if was a billion years old it could have come from anywhere in the galaxy. And it could easily be older than that (there are lots of stars billions of years older than the sun).  But it did not come from some other galaxy, since otherwise the galactic field would have made it much faster.  Likewise probably not from the center, where even if escaped its star it would not get out this far.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jgoldader on 10/29/2017 12:33 PM
Very interesting find. Too bad we don't have a spaceprobe ready (and a drive to match) to go catch it and investigate it... But next time one of these comes around, we might be ready.

I keep thinking that as well.  There've been a number of close approaches of interesting objects, and it's a pity we've no way to get a small probe into the path of one to get a few images and spectra as they pass.  You'd need to have a smallest with an upper stage, already in Earth orbit (high orbit?  GEO?) ready to go; but perhaps orbital mechanics are so cruel that such things are the stuff of fantasy.

It's a pity the engine on Japan's Procyon satellite failed.  That was a nice mission, a smallsat designed for an asteroid flyby, and who knows when we'll get to test that concept again.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 10/29/2017 12:48 PM
Looks like a rock from this galaxy could be pretty close to as old as the universe??!

Methuselah star, only 190 ly away, estimated age 14.46 ± 0.8 billion years. (assumed not actually older than the universe, of course)
population II so metal poor but possibly has oxygen, silicon etc, so I guess it is at least slightly possible for an icy, rocky object in this galaxy to be as old.

https://en.wikipedia.org/wiki/HD_140283
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 10/29/2017 05:49 PM
Looks like a rock from this galaxy could be pretty close to as old as the universe??!

Methuselah star, only 190 ly away, estimated age 14.46 ± 0.8 billion years. (assumed not actually older than the universe, of course)
population II so metal poor but possibly has oxygen, silicon etc, so I guess it is at least slightly possible for an icy, rocky object in this galaxy to be as old.

https://en.wikipedia.org/wiki/HD_140283

And coincidentally there’s this new video about this very star. Though he’s not a scientist I think this guy does some of the best short form videos on topics like this.

https://www.youtube.com/watch?v=x6TYVlE8HNc
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/29/2017 06:43 PM
Very interesting find. Too bad we don't have a spaceprobe ready (and a drive to match) to go catch it and investigate it... But next time one of these comes around, we might be ready.

Eric Mamajek had an interesting take on that https://twitter.com/EricMamajek/status/924010707271553026
Quote
Flyby or sample return to interstellar asteroid A/2017 U1 = exploring small exoplanetary world in our backyard:10s of km/s easier than 0.1c!
Yes, it's pretty ridiculous to think about chasing this thing down, but compared to something like Breakthrough Starshot it would be a total piece of cake. Launching at mere 0.001c to chase something like this down could be a great test run ;D

In practice, there's another problem though: It will be invisible to our biggest telescopes very soon, and the uncertainties on the trajectory would make it very, very hard to find years down the road.

Having an interceptor ready for the next one seems much more practical. We often see Oort cloud comets years out, so even with the extra interstellar velocity there's a chance of having a reasonable amount of notice for other objects. OTOH, it may prove difficult to convince anyone to fund a mission on the argument that a suitable target will eventually appear...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: alang on 10/29/2017 07:23 PM
:) Not too seriously.

The object's trajectory in and out of the Solar system follows the flight path of a  covert system survey mission as describe in some of the more esoteric Sci-Fi literature.

But, perhaps they build in threes :-)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/29/2017 08:37 PM
how does one (basically) interpret the direction the object came from?  The galactic plane is different from the solar system orbital plane.  I just hit the limit of Google fu.
You can plug the RA/DEC from https://projectpluto.com/temp/2017u1.htm into any planetarium software, star chart site etc. However... which stars appear in that direction now does not tell you anything about possible sources, you have to account for the stars motion. Stars move a lot on tens of thousands of years timescales.

The animation on https://twitter.com/tony873004/status/924343154660098048 gives a good idea how much this matters.

People have work on this stuff have already looked and found it's not obviously traceable back to any local star, see comments from Mamajek upthread (http://forum.nasaspaceflight.com/index.php?topic=44075.msg1743076#msg1743076).
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Phil Stooke on 10/29/2017 08:50 PM
"how does one (basically) interpret the direction the object came from?  The galactic plane is different from the solar system orbital plane. "


https://web.njit.edu/~gary/321/Lecture18.html (https://web.njit.edu/~gary/321/Lecture18.html)

This website has math for it, but it also has a nice chart showing both RA/DEC coordinates and galactic coordinates.  A bit of a mess, but you can plot a position in RA/DEC and figure out where that is relative to the galactic equator and poles.  This could be superimposed over a map of constellations if you like. 

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 10/29/2017 11:03 PM
In practice, there's another problem though: It will be invisible to our biggest telescopes very soon, and the uncertainties on the trajectory would make it very, very hard to find years down the road.
Having a really accurate trajectory would be fun.. I wonder how far back in time we could extrapolate it's journey.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 10/30/2017 12:14 AM
Palomar Optical Spectrum of Hyperbolic Near-Earth Object A/2017 U1 (https://arxiv.org/abs/1710.09977)

We present optical spectroscopy of the recently discovered hyperbolic near-Earth object A/2017 U1, taken on 25 Oct 2017 at Palomar Observatory. Although our data are at a very low signal-to-noise, they indicate a very red surface at optical wavelengths without significant absorption features.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 10/30/2017 01:13 AM
Palomar Optical Spectrum of Hyperbolic Near-Earth Object A/2017 U1 (https://arxiv.org/abs/1710.09977)

We present optical spectroscopy of the recently discovered hyperbolic near-Earth object A/2017 U1, taken on 25 Oct 2017 at Palomar Observatory. Although our data are at a very low signal-to-noise, they indicate a very red surface at optical wavelengths without significant absorption features.

What does that red likely indicate? Iron Oxide? Other possibilities?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Dalhousie on 10/30/2017 01:26 AM
Palomar Optical Spectrum of Hyperbolic Near-Earth Object A/2017 U1 (https://arxiv.org/abs/1710.09977)

We present optical spectroscopy of the recently discovered hyperbolic near-Earth object A/2017 U1, taken on 25 Oct 2017 at Palomar Observatory. Although our data are at a very low signal-to-noise, they indicate a very red surface at optical wavelengths without significant absorption features.

What does that red likely indicate? Iron Oxide? Other possibilities?

I would guess Tholins
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 10/30/2017 01:29 AM
Was going to post same. Here are some links:
https://www.nasa.gov/nh/pluto-the-other-red-planet
https://en.wikipedia.org/wiki/Makemake#Spectra_and_surface
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 10/30/2017 09:50 AM
As I understand it, A/2017 U1 is moving at about 26km/s relative to the solar system which is (or so I am led to understand) about the average velocity spread between the Sun and other nearby stars (~30km/s, to be specific).

How much can we infer from this? Does this mean that the object is a member of the family of objects born in the same molecular cloud as The Sun? Does that also mean that we should expect a co-moving group of stars should also have a 'corona' of ejected objects moving in between them?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/30/2017 04:35 PM
How much can we infer from this? Does this mean that the object is a member of the family of objects born in the same molecular cloud as The Sun?
No, the opposite. The Sun's birth cluster dispersed long ago. A/2017 U1 has the same sort of velocity as random field stars, so its potential origins diverse as they are.  As Bynaus pointed out
Regarding orgins, there is a simple short-hand to estimate travel distances: for each km/s at infinity, the object will travel about a parsec per million years. So for this one, 25 parsecs (~82 light years) per million year. Even if it travelled only a few million years, it could have come from very far away!

Does that also mean that we should expect a co-moving group of stars should also have a 'corona' of ejected objects moving in between them?
We already pretty much knew this would be the case: We've seen quite a few solar system objects become slightly hyperbolic through interactions with planets, and have very good reason to believe the same happens elsewhere. There was a lot of uncertainty about how common such objects are, and A/2017 U1 may help answer that.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/30/2017 04:42 PM
Karen Meech and collaborators recieved HST DDT for this object
 Which way home? Finding the origin of our Solar System's first interstellar visitor (http://www.stsci.edu/cgi-bin/get-proposal-info?id=15405&observatory=HST)

Quote
We request HST/WFC3/UVIS observations of A/2017 U1, a recently discovered fast moving and fast fading object that appears to originate from outside the Solar System. Rapid follow-up observations from the ground established the object's orbit as hyperbolic and thus ruled out that A/2017 U1 is a comet or asteroid. The proposed observations are critical to (a) determine the object's rotation period in order to allow observations to be performed at maximal brightness, and (b) obtain precise astrometry along an extended arc length in order to identify the region from which this object originated.

A/2017 U1 is the first known interloper from outside the Solar System, and the observations proposed here play a pivotal role in determining its origin.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 10/30/2017 05:35 PM
We already pretty much knew this would be the case: We've seen quite a few solar system objects become slightly hyperbolic through interactions with planets, and have very good reason to believe the same happens elsewhere. There was a lot of uncertainty about how common such objects are, and A/2017 U1 may help answer that.

That it is probably rocky is (as you've said above) somewhat surprising. But that does make me wonder if *some* of the slightly hyperbolic objects we've seen before might actually be interstellar visitors ...

Edit: my reasoning might not be clear here: if you assume the majority of ejected material is icy i.e. that this one atypical and that we didn't just get lucky, then some of the e~=1.05 objects being interstellar visitors would make the composition distribution closer to that predicted.

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 10/30/2017 06:22 PM
Edit: my reasoning might not be clear here: if you assume the majority of ejected material is icy i.e. that this one atypical and that we didn't just get lucky, then some of the e~=1.05 objects being interstellar visitors would make the composition distribution closer to that predicted.
The Engelhardt paper linked earlier (https://arxiv.org/abs/1702.02237) also suggests this is possible
Quote
Some of the synthetic detected ISOs had eccentricities as small as 1.01 --- in the range of the largest eccentricities of several known comets.
One obvious question though is why we haven't seen any faster ones.  e=~1 represents an extreme end of the distribution, so naively if any of our e=~1 comets are interstellar, one would expect to see at least a few which were more obviously hyperbolic. Figure 5 from the above paper attached.

Also notable in this figure, A/2017 U1 fits reasonably well in the asteroid predictions.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 10/30/2017 06:44 PM
Well, maybe if the orbit can be determined with enough accuracy (precovery images?), one could still consider to build a nuclear-ion-propelled probe (with a big delta-v reserve) and send it after it. It might take decades to chase it down, but it could well be worth it - as Mamajek writes, we will never get so close to exoplanetary objects anytime soon. Even if we find another one a few decades from now, each of these exoasteroids should be unique as each (in all likelyhood) represents a different exoplanetary system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: redliox on 10/30/2017 07:17 PM
I don't supposed a request has been made from the Hubble yet?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Johnnyhinbos on 10/30/2017 07:29 PM
I don't supposed a request has been made from the Hubble yet?
I believe if you look a few posts upthread you will see that the request has already been made to HST...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: missinglink on 10/30/2017 09:12 PM
:) Not too seriously.

The object's trajectory in and out of the Solar system follows the flight path of a  covert system survey mission as describe in some of the more esoteric Sci-Fi literature.

I immediately thought of this passage, in Peter Watts' novel Blindsight. This is describing the course change performed by Theseus, the spaceship sent to survey the mysterious aliens who took pictures of Earth and then disappeared:

Quote
She'd taken us a good fifteen AUs towards our destination before something scared her off course. Then she'd skidded north like a startled cat and started climbing: a wild high three-gee burn off the ecliptic, thirteen hundred tonnes of momentum bucking against Newton's First.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Zed_Noir on 10/30/2017 09:35 PM
:) Not too seriously.

The object's trajectory in and out of the Solar system follows the flight path of a  covert system survey mission as describe in some of the more esoteric Sci-Fi literature.

I immediately thought of this passage, in Peter Watts' novel Blindsight. This is describing the course change performed by Theseus, the spaceship sent to survey the mysterious aliens who took pictures of Earth and then disappeared:

Quote
She'd taken us a good fifteen AUs towards our destination before something scared her off course. Then she'd skidded north like a startled cat and started climbing: a wild high three-gee burn off the ecliptic, thirteen hundred tonnes of momentum bucking against Newton's First.

Was remembering some passage from the ancient Lensman series novels from E.E. "Doc" Smith  ;)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 10/31/2017 11:47 PM
Kinematics of the Interstellar Vagabond A/2017 U1 (https://arxiv.org/abs/1710.11364)

The initial Galactic velocity vector for the recently discovered hyperbolic asteroid A/2017 U1 is calculated for before its encounter with our solar system. When the velocity is compared to the local stars, A/2017 U1 can be easily ruled out as co-moving with any of the dozen nearest systems, i.e. it does not appear to be associated with any local exo-Oort clouds (most notably that of the Alpha Centauri triple system). The object's velocity is within 5 km/s of the mean Galactic velocity of the stars in the solar neighborhood (<25 pc), so its velocity would appear to be typical for that of a body whose velocity was drawn from the Galactic velocity distribution of the local stars. These calculations strengthen the interpretation that A/2017 U1 has a distant extrasolar origin, but not among the very nearest stars.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Zed_Noir on 11/01/2017 01:10 AM
@Mongo62
 So we can call A/2017 U1 a "Rogue Dwarf Planet"?  ;D
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/02/2017 01:11 AM
Pole, Pericenter, and Nodes of the Interstellar Minor Body A/2017 U1 (https://arxiv.org/abs/1711.00445)

Here, we explore some peculiar orbital features of the recently discovered asteroid A/2017 U1, which is a clear outlier when considering the average value of the eccentricity of known hyperbolic comets. As for the orientation of its orbit in space, the orbital plane of A/2017 U1 seems to be away from any obvious clusters present for this population. The orbital nodes of A/2017 U1 are well away from the paths of the planets of the Solar System and the Sun. All these orbital properties appear to confirm A/2017 U1 as the first known interstellar asteroid.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/02/2017 03:45 AM
Anyone know if there have been faster speeds recorded?
Near-hyperbolic sungrazers have a maximum speed similar to escape velocity at the solar "surface", for example, Wikipedia gives C/2011 W3 (Lovejoy) (https://en.wikipedia.org/wiki/C/2011_W3_(Lovejoy)) perihelion speed as 565 km/s. Of course, they drop back to normal speeds as they climb back out, in the rare cases that survive.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 11/02/2017 10:16 AM
IIRC, the actual (and most accurate) speed measurement for objects passing through the inner solar system is vinf, being the projected relative velocity to the sun at aphelion where a approaches infinity.


EDIT
Apparently, the proper abbreviation for 'semi-major axis' is 'a', which is a knew bit of knowledge for me!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/02/2017 11:16 AM
Anyone know if there have been faster speeds recorded?
Near-hyperbolic sungrazers have a maximum speed similar to escape velocity at the solar "surface", for example, Wikipedia gives C/2011 W3 (Lovejoy) (https://en.wikipedia.org/wiki/C/2011_W3_(Lovejoy)) perihelion speed as 565 km/s. Of course, they drop back to normal speeds as they climb back out, in the rare cases that survive.

Or as I prefer to think of it, Lovejoy peaked at 0.188% of light speed. That's fast!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 11/02/2017 03:35 PM
You'd need two images that the object appears in, presumably with very fast objects it'd only appear in one image.

Secondly how often would an object pass by that was moving at a velocity very different to the galactic orbital speed of the solar system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/02/2017 05:13 PM
Is there any rationale as to why nobody has detected very very fast objects going thru the solar system?  What I mean is, asteroids clocking above 1000 km/s.
There is pretty good reason to believe that the bulk of the population of interstellar objects will have velocities similar to nearby stars, under maybe ~100 km/s (Vinf) relative the Sun. Given that we've only detected one unambiguously interstellar object, we wouldn't expect many at the extremes. So the fact we haven't seen 1000 km/s objects is not a surprise.

Would we detect super fast objects if they were there? My off the cuff guess is something the size of 2017 U1 would go undetected, but we'd have a good chance at significantly larger / brighter objects. Apparent motion depends on the speed and distance, so surveys optimized for NEOs should still spot more distant fast, bright objects (for suitably hand-wavy values of "distant, "fast" and "bright")
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/02/2017 07:03 PM
David Trilling and collaborators received 32.6 hours of Spitzer DDT time for this object

http://ssc.spitzer.caltech.edu/warmmission/scheduling/approvedprograms/ddt/13249.txt

Quote
We propose to observe the newly discovered interstellar comet A/2017 U1 to
measure its diameter and albedo. Little is known about this object, which
presumably formed in another planetary system. This is the only opportunity
*ever* to determine the albedo of this object, which will help us understand
how planetary system formation in other systems compares to what occurred
in our Solar System. The proposed observations - requiring 32.6 hours in
late November - are the last telescopic observations that will ever be made
of this object. The return from these proposed observations would be
tremendous - characterizing the first ever known object from beyond our
Solar System. Because the object is faint and fading, these observations
must be made as soon as possible.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/03/2017 02:02 AM
How much damage would it have done if it hit the Earth?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 11/03/2017 09:44 AM
It's a 100m-class rocky body. However, it's relative speed is so high so it is possible that it would have just been a dramatic air-burst because of the rate at which heat would have built up when entering the atmosphere.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/07/2017 01:29 AM
Origin of Interstellar Object A/2017 U1 in a Nearby Young Stellar Association? (https://arxiv.org/abs/1711.01300)

We suggest that the kinematics and properties of interstellar object A/2017 U1 point towards its formation in a protoplanetary disk in the ~45 Myr-old Carina or Columba young stellar associations, and subsequent ejection with a low peculiar velocity (1-2 km/sec) during or soon after planet formation inside the ice line. This scenario predicts that the Solar System will encounter more such objects with radiants similar to that of A/2017 U1.

Implications for planetary system formation from interstellar object A/2017 U1 (https://arxiv.org/abs/1711.01344)

The recently discovered minor body A/2017 U1 is the first known object in our Solar System that is not bound by the Sun's gravity. Its hyperbolic orbit (eccentricity greater than unity) strongly suggests that it originated outside our Solar System; its red color is consistent with substantial space weathering experienced over a long interstellar journey. We carry out an order of magnitude calculation of the probability of detecting such an object. We find that the observed detection rate of U1-like objects can be satisfied if the average mass of ejected material from nearby stars during the process of planetary formation is ~20 Earth masses, similar to the expected value for our Solar System. The current detection rate of such interstellar interlopers is estimated to be 0.2/year, and the expected number of detections over the past few years is almost exactly one. When the Large Synoptic Survey Telescope begins its wide, fast, deep all-sky survey the detection rate will increase to 1/year. This will provide further constraints on nearby planetary system formation through a better estimate of the number and properties of interstellar objects.

The rotation period and shape of the hyperbolic asteroid A/2017 U1 from its lightcurve (https://arxiv.org/abs/1711.01402)

We observed the newly discovered hyperbolic minor planet A/2017 U1 on 2017 October 30 with the 4.3-m Discovery Channel Telescope. From these observations, we derived a partial lightcurve with variability of at least 1.2 mag. This lightcurve segment rules out rotation periods less than 3 hr and suggests the period is at least 5 hr. On the assumption that the variability is due to a changing cross section, the axial ratio is at least 3:1. We saw no evidence for a coma or tail in either individual images or in a stacked image having an equivalent exposure time of 9000 s, and set a limit to any coma present at less than ~30 mag arcsec^-2.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/07/2017 06:58 AM
The IAU has introduced a new "I" series for interstellar objects.

Quote
A new series of small-body designations for interstellar objects will be introduced: the I numbers.

Hence A/2017 U1 has been designated:

Quote
Accordingly, the object A/2017 U1 receives the permanent designation 1I
and the name 'Oumuamua.  The name, which was chosen by the Pan-STARRS team, is
of Hawaiian origin and reflects the way this object is like a scout or
messenger sent from the distant past to reach out to us ('ou means reach out
for, and mua, with the second mua placing emphasis, means first, in advance of).

The full text is here https://www.minorplanetcenter.net/mpec/K17/K17V17.html (https://www.minorplanetcenter.net/mpec/K17/K17V17.html)

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 11/07/2017 07:05 AM
I wonder if any other objects will be retroactively redesignated with the 'I' suffix as analysis of 1I's behaviour increases the likelihood that past objects also had exo-system origins?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/07/2017 07:17 AM
I wonder if any other objects will be retroactively redesignated with the 'I' suffix as analysis of 1I's behaviour increases the likelihood that past objects also had exo-system origins?

It's possible, though I doubt it.  There are a few objects with 1 < e < 1.05 and some are suspected to be interstellar (can't remember exactly where I read this) but I doubt any can be shown to be definitely interstellar in origin as this eccentricity can happen by perturbation and we can't do follow-up to be more certain as they are hyperbolic ...

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: missinglink on 11/07/2017 07:40 AM
It's a 100m-class rocky body. However, it's relative speed is so high so it is possible that it would have just been a dramatic air-burst because of the rate at which heat would have built up when entering the atmosphere.
I've been worried about planetary defense from comets (not asteroids) because they are so much faster, giving shorter advance warning times as well as making a bigger impact when they hit. Now you're saying that faster can be better if they burn up in the atmosphere before hitting the ground?
That would be reassuring. If relative speed goes even higher, though (hundreds of km/s), won't the object simply punch through the atmosphere like it was thin tissue paper, with no time for an air burst?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ugordan on 11/07/2017 07:44 AM
Now you're saying that faster can be better if they burn up in the atmosphere before hitting the ground?

It's not better, all that energy still needs to be deposited somewhere. Chelyabinsk was an oblique entry and for all intents and purposes quite a high airburst yet it did noticeable damage below due to shockwave overpressure.

Not to mention the Tunguska event.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/07/2017 12:33 PM
Now you're saying that faster can be better if they burn up in the atmosphere before hitting the ground?

It's not better, all that energy still needs to be deposited somewhere. Chelyabinsk was an oblique entry and for all intents and purposes quite a high airburst yet it did noticeable damage below due to shockwave overpressure.

Not to mention the Tunguska event.

My understanding is that while Tunguska produced a somewhat larger airburst than Chelyabinsk, it did far more damage, mainly because being a mechanically stronger object, it exploded at a considerably lower height, in the 5-10 kilometer range. The Chelyabinsk event was in the megaton range itself, but too high (23.3 km) to do much damage other than shatter windows.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ugordan on 11/07/2017 12:55 PM
Last time I checked, Chelyabinsk was estimated at 500 kt. Tunguska estimates range widely, with a recent trend of lowering the estimated yield based on the fact the shockwave is not spherically symmetrical like in a nuclear airburst, but the energy is more or less downward-concentrated. The estimates now appear to put it at up to 5 Mt.

So Tunguska was up to 10x times more energetic, not just "somewhat larger". Granted, the airburst height will have a large affect on ground overpressure, but my point is by no means does an airburst guarantee you won't see ground damage.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 11/07/2017 01:04 PM
@Mongo62
 So we can call A/2017 U1 a "Rogue Dwarf Planet"?  ;D

It's too small to be eligible to be considered a dwarf planet.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/07/2017 01:36 PM
Its worth mentioning the impact effects calculator here:

http://impact.ese.ic.ac.uk/ImpactEffects/

For this object (160 m diameter, 2000 kg/m3 density, 45 km/s impact velocity), you get an impact energy of about 1 Gigaton (about 20 Tsar bombs), and a final crater diameter of 4 km.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/08/2017 12:58 AM
On the Consequences of the Detection of an Interstellar Asteroid (https://arxiv.org/abs/1711.02260)

The arrival of the robustly hyperbolic asteroid A/2017 U1 has potentially interesting ramifications for the planet-formation process. Although extrapolations from a sample size of one are necessarily uncertain, order-of-magnitude estimates suggest that the Galaxy contains a substantial mass in similar bodies. We argue that despite its lack of Coma, A/2017 U1 likely contained a significant mass fraction of volatile components, and we argue that its presence can be used to infer a potentially large population of as-yet undetected Neptune-like extrasolar planets.

1I/'Oumuamua is Hot: Imaging, Spectroscopy and Search of Meteor Activity (https://arxiv.org/abs/1711.02320)

1I/2017 U1 ('Oumuamua), a recently discovered asteroid in hyperbolic orbit, is likely the first macroscopic object of extrasolar origin identified in the solar system. Here, we present imaging and spectroscopic observations of 'Oumuamua using the Hale Telescope as well as a search of meteor activity potentially linked to this object. We find that 'Oumuamua exhibits a moderate spectral gradient of 10%±6% (100 nm)−1, a value significantly lower than that of outer solar system bodies, indicative of a formation and/or previous residence in a warmer environment. Imaging, spectral and meteor observations show no evidence that 'Oumuamua is presently or has been recently active. No obvious candidate stars are proposed as the point of origin for 'Oumuamua. Given a mean free path of ∼109~ly in the solar neighborhood, 'Oumuamua has likely spent a very long time in the interstellar space before encountering the solar system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/10/2017 07:22 AM
Project Lyra: Sending a Spacecraft to 1I/'Oumuamua (former A/2017 U1), the Interstellar Asteroid (https://arxiv.org/abs/1711.03155)
Andreas M. Hein, Nikolaos Perakis, Kelvin F. Long, Adam Crowl, Marshall Eubanks, Robert G. Kennedy III, Richard Osborne

Quote
The first definitely interstellar object 1I/'Oumuamua (previously A/2017 U1) observed in our solar system provides the opportunity to directly study material from other star systems. Can such objects be intercepted? The challenge of reaching the object within a reasonable timeframe is formidable due to its high heliocentric hyperbolic excess velocity of about 26 km/s; much faster than any vehicle yet launched. This paper presents a high-level analysis of potential near-term options for such a mission. Launching a spacecraft in a reasonable timeframe of 5-10 years requires a hyperbolic solar system excess velocity between 33 to 76 km/s for mission durations between 30 to 5 years. Different mission durations and their velocity requirements are explored with respect to the launch date, assuming direct impulsive transfer to the intercept trajectory. Several technology options are outlined, ranging from a close solar Oberth Maneuver using chemical propulsion, and the more advanced options of solar and laser sails. To maximize science return decelerating the spacecraft at 'Oumuamua is highly desirable, due to the minimal science return from a hyper-velocity encounter. It is concluded that although reaching the object is challenging, there seem to be viable options based on current and near-term technology.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 11/10/2017 10:38 AM
Question based on curiosity: Could a spacecraft capable of such high velocities (and, likely, sustained acceleration) as needed to intercept Oumuamua-class objects be practical for true interstellar missions to such targets as Proxima-b? More propellent would obviously be indicated as well as a long-duration power system and long-range communications system but nothing is obviously unthinkable, especially as any interception of Oumuamua-class objects would most likely be in broadly the same domain as currently being traversed by Voyager-1.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 11/10/2017 10:48 AM
You'd need to be moving about 27 km/s in relation to the sun at infinity to catch up with Oumuamua, or 50km/s at 1AU.

To get to Proxima B would then take another 47,000 years.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/10/2017 06:06 PM
To get to Proxima B would then take another 47,000 years.
Yeah, catching 'Oumuamua requires a few x faster than Voyager, which is nothing on interstellar scales. OTOH, if one thinks that something like Breakthrough Starshot could be launched in the next few decades, this should be an absolute piece of cake in comparison: 1/100th the performance would be overkill. YMMV as to how this speaks to the credibility of the respective proposals ;)

One issue not addressed in the Hein preprint is actually finding  'Oumuamua again. It was barely visible in ~meter class telescopes when it was ~1 au from the Sun and < 1 au from Earth. At the proposed intercept distances of tens of au from the Sun, it will be thousands of times fainter. So unless the spacecraft has an absurdly large telescope, the trajectory would need to be known precisely enough to get within a fraction of an au blind. Given that it will be too faint for Hubble within a couple months, this seems very unlikely.

edit:
To be fair, they do touch on the problem briefly, but without any numbers:
Quote
The small size of the object and its low albedo will make it difficult to observe it once it has entered deep space again. This means the navigation problem of getting a sufficiently accurate fix on 1I/‘Oumuamua to get close enough to the object to send back useful data is considerable. Due to the positional uncertainty of such a difficult-to-track object, a distributed, swarm-based mission design that is able to span a large area, should be investigated.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/13/2017 01:20 AM
A short but particularly interesting paper:

The origin of interstellar asteroidal objects like 1I/2017 U1 (https://arxiv.org/abs/1711.03558)

Quote
With the recently discovered interstellar object 1I/2017U1 (1I/'Oumuamua) we have to realize that the Solar System is not isolated, but part of a larger environment with which we interact. We compare the kinematics of 1I/2017U1 with simulations of the Milky Way Galaxy and Gaia TGAS data to estimates the local density of objects similar to 1I/2017U1 and to investigate its possible origin. We find that about 1.3 Myr ago 1I/2017U1 has passed within a distance of 0.16 pc from the nearby star TYC4742-1027-1. It seems unlikely that 1I/2017U1 originated from an Oort-cloud around this star, but it simply trespassed on its way through.

Based on our calculations we conclude that the population of sola lapis (unbound asteroidal objects) is much larger than that of cometary objects. The number of objects with characteristics similar to 1I/2017U1 must be very common, we estimate a population density of ≈3×10^5 similarly sized objects within 100 au from the Sun or ∼10^14 per cubic parsec in the Solar neighborhood. By comparing the results of simulations of the Milky Way Galaxy with the Gaia DR1 TGAS we conclude that the kinematics of 1I/2017U1 is consistent with that expected from interstellar distribution of isolated objects that are part of the local Galactic potential. It is then hard to predict how long 1I/2017 U1 has been roaming the Galaxy before it visited the Solar System.

We subsequently argue that the Galaxy is rich in solae lapides such as 1I/2017U1. We speculate that such an object is formed in a debris disk as left over from the star and planet formation process. Upon interaction with other stars in the parental star cluster or due to resonant interactions within the planetary disk these objects are liberated from their parental star and float freely in the interstellar space. We just met 1I/2017 U1 by chance, and with the derived mean Galactic density we expect such visitors to be very common.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Lar on 11/13/2017 02:07 AM
if the expectation is that such visitors are likely to be common, what changed? That is, why is this the first one detected? Did we gain some big new capability that lets us find them where previously we could not?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/13/2017 04:42 AM
if the expectation is that such visitors are likely to be common, what changed? That is, why is this the first one detected?
"Common" is relative. The paper tries to infer how many are out there based on the fact that Pan-STARRS has detected one in it's operational lifetime. It definitely doesn't imply that we should have seen more, but is does suggest that there many thousands passing through the larger solar neighborhood.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ugordan on 11/13/2017 06:26 AM
That is, why is this the first one detected?

The answer may lie in the fact that this particular object happened to fly fairly close to Earth on its outbound leg.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/13/2017 07:21 AM
if the expectation is that such visitors are likely to be common, what changed? That is, why is this the first one detected?
"Common" is relative. The paper tries to infer how many are out there based on the fact that Pan-STARRS has detected one in it's operational lifetime. It definitely doesn't imply that we should have seen more, but is does suggest that there many thousands passing through the larger solar neighborhood.

There is an expectation that when LSST is operational (first light 2019), that we will find quite a lot more ... and hopefully much earlier.

Objects like this are our easiest way of studying extrasolar material; way easier than visiting, say, proxima Centauri.

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/13/2017 07:40 AM
A short but particularly interesting paper:

The origin of interstellar asteroidal objects like 1I/2017 U1 (https://arxiv.org/abs/1711.03558)

Quote
With the recently discovered interstellar object 1I/2017U1 (1I/'Oumuamua) we have to realize that the Solar System is not isolated, but part of a larger environment with which we interact. We compare the kinematics of 1I/2017U1 with simulations of the Milky Way Galaxy and Gaia TGAS data to estimates the local density of objects similar to 1I/2017U1 and to investigate its possible origin. We find that about 1.3 Myr ago 1I/2017U1 has passed within a distance of 0.16 pc from the nearby star TYC4742-1027-1. It seems unlikely that 1I/2017U1 originated from an Oort-cloud around this star, but it simply trespassed on its way through.

Based on our calculations we conclude that the population of sola lapis (unbound asteroidal objects) is much larger than that of cometary objects. The number of objects with characteristics similar to 1I/2017U1 must be very common, we estimate a population density of ≈3×10^5 similarly sized objects within 100 au from the Sun or ∼10^14 per cubic parsec in the Solar neighborhood. By comparing the results of simulations of the Milky Way Galaxy with the Gaia DR1 TGAS we conclude that the kinematics of 1I/2017U1 is consistent with that expected from interstellar distribution of isolated objects that are part of the local Galactic potential. It is then hard to predict how long 1I/2017 U1 has been roaming the Galaxy before it visited the Solar System.

We subsequently argue that the Galaxy is rich in solae lapides such as 1I/2017U1. We speculate that such an object is formed in a debris disk as left over from the star and planet formation process. Upon interaction with other stars in the parental star cluster or due to resonant interactions within the planetary disk these objects are liberated from their parental star and float freely in the interstellar space. We just met 1I/2017 U1 by chance, and with the derived mean Galactic density we expect such visitors to be very common.

I see they didn’t bother using its ‘common’ name, which most of the more recent papers seem too.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Blackstar on 11/13/2017 12:10 PM
A new paper addresses how one might launch a space mission to this object:

https://arxiv.org/abs/1711.03155

I have attached the paper.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Dao Angkan on 11/13/2017 09:23 PM
That is, why is this the first one detected?

The answer may lie in the fact that this particular object happened to fly fairly close to Earth on its outbound leg.

Right, it's hard to make statistics off of a sample of one, but the fact that one has come so close to Earth, within only a few years of operation for this instrument (which isn't even specifically designed to detect extra-solar visitors) suggests that these bodies could be quite common. Now we can consider potential surveys which would be optimised to specifically search for extra-solar visitors.

If we have a survey which starts to regularly detect these objects, then maybe we can have a realistic chance to design a mission to visit one.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Dao Angkan on 11/13/2017 09:36 PM
A new paper addresses how one might launch a space mission to this object:

https://arxiv.org/abs/1711.03155

I have attached the paper.

This was posted above, it's an interesting paper, but I think a more realistic proposition would be to have a survey specifically searching for these objects so that we can launch a probe at short notice.

The "solar fry-by" sounds interesting, but seems to fly even closer than the Parker Solar Probe, although admittedly only once, so may be reasonable, still, it's pretty low TRL. Is there another mission we could try the "solar fry-by" on as a technology demonstrator?

If refueled BFR and "solar fry-by" both come to fruition, then that would open up some amazing opportunities for outer-solar system exploration.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/13/2017 09:47 PM
If we have a survey which starts to regularly detect these objects, then maybe we can have a realistic chance to design a mission to visit one.
And unless this was a fluke LSST (https://en.wikipedia.org/wiki/Large_Synoptic_Survey_Telescope) should be that survey.

The Cook et al paper linked earlier (https://arxiv.org/abs/1607.08162) predicted LSST should detect between 0.0001 and 1 interstellar object per year. The fact Pan-STARRS spotted one suggests the real number is on the high end of that estimate.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/15/2017 01:12 PM
APO Time Resolved Color Photometry of Highly-Elongated Interstellar Object 1I/'Oumuamua (https://arxiv.org/abs/1711.04927)

We report on the g, r and i band observations of the Interstellar Object 1I/'Oumuamua taken on 2017 October 29 from 04:28 to 08:40 UTC from the Apache Point Observatory (APO) 3.5m telescope's ARCTIC camera. We use these observations to estimate object colors, and find them to be g−r=0.41±0.24 and r−i=0.23±0.25, consistent with visible spectra (Masiero 2017; Ye et al. 2017; Fitzsimmons et al. 2017) and most comparable to the population of Solar System C/D asteroids, Trojans, or comets, although we find no evidence of any cometary activity, even 1.5 months after 1I/'Oumuamua's close flyby of the Sun. Significant brightness variability was seen in the r observations, with the object becoming notably brighter towards the end of the run. By combining our APO photometric time series data with the Discovery Chanel Telescope (DCT) data of Knight et al. 2017 taken 20 h later on 2017 October 30, we construct an almost complete lightcurve with a most probable lightcurve period of P≃4 h, and reveal the most useful locations during 1I/'Oumuamua's rotation phase for additional data to improve constraints on its lightcurve. This implies a double peaked rotation period of 8.1 ± 0.02 h, with a peak-to-peak amplitude of 1.5 - 2.1 mags. The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9 and is rotating below its critical break up limit for most viable values of density and cohesive strength within the range of rotation periods and axial ratios compatible with our data. Our results are compatible with 1I/'Oumuamua having a density > 1.0 g cm−3 or having modest cohesive strength. Astrometry useful for constraining the object's orbit was also obtained and published in Weaver et al. 2017.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/15/2017 08:45 PM
The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9
They note in the paper that this is pretty far outside the normal range for known solar system objects in this size range. For perspective, I'd think of Itokawa as an example of a fairly oblong asteroid, but it's only ~2.

Both APO and DCT seem to support this extreme lightcuve (and IIRC there were hints from earlier observation) so it's not likely to be totally in error.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/15/2017 08:48 PM
The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9
They note in the paper that this is pretty far outside the normal range for known solar system objects in this size range. For perspective, I'd think of Itokawa as an example of a fairly oblong asteroid, but it's only ~2.

Both APO and DCT seem to support this extreme lightcuve (and IIRC there were hints from earlier observation) so it's not likely to be totally in error.

Anybody do a spectrograph of the reflected light yet?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/15/2017 09:35 PM
Anybody do a spectrograph of the reflected light yet?
Yes, see this post (http://forum.nasaspaceflight.com/index.php?topic=44075.msg1743478#msg1743478) and the second paper in this post (http://forum.nasaspaceflight.com/index.php?topic=44075.msg1747041#msg1747041). Others have also obtained spectra that aren't published yet but are generally similar, for example Alan Fitzsimmons tweeted this one (https://twitter.com/FitzsimmonsAlan/status/923928561722982400).

The tl;dr is that it's featureless (no obviously identifiable absorption features) with a red slope (reflects more at longer wavelengths than shorter ones). This is similar to some asteroids and KBOs, but that doesn't necessarily mean they are made of the same stuff.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: eric_astro on 11/15/2017 09:36 PM
You'd need to be moving about 27 km/s in relation to the sun at infinity to catch up with Oumuamua, or 50km/s at 1AU.

To get to Proxima B would then take another 47,000 years.

But if you woke up in 47,000 years, Proxima would be at about 3 light years from earth!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/15/2017 11:20 PM
The two values imply that 1I/'Oumuamua has an axial ratio of 4.1 to 6.9
They note in the paper that this is pretty far outside the normal range for known solar system objects in this size range. For perspective, I'd think of Itokawa as an example of a fairly oblong asteroid, but it's only ~2.

Both APO and DCT seem to support this extreme lightcuve (and IIRC there were hints from earlier observation) so it's not likely to be totally in error.
Weird. Surely this would be a binary? A ratio of 6.9 would be like a skinny finger.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/16/2017 01:42 AM
Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes (https://arxiv.org/abs/1711.05687)

We present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua) taken during its 2017 October flyby of Earth. The optical colors B-V = 0.70±0.06, V-R = 0.45±0.05, overlap those of the D-type Jovian Trojan asteroids and are incompatible with the ultrared objects which are abundant in the Kuiper belt. With a mean absolute magnitude HV = 22.95 and assuming a geometric albedo pV = 0.1, we find an average radius of 55 m. No coma is apparent; we deduce a limit to the dust mass production rate of only ∼ 2×10^−4 kg s−1, ruling out the existence of exposed ice covering more than a few m2 of the surface. Volatiles in this body, if they exist, must lie beneath an involatile surface mantle ≳0.5 m thick, perhaps a product of prolonged cosmic ray processing in the interstellar medium. The lightcurve range is unusually large at ∼2.0±0.2 magnitudes. Interpreted as a rotational lightcurve the body has semi-axes ∼230 m × 35 m. A ∼6:1 axis ratio is extreme relative to most small solar system asteroids and suggests that albedo variations may additionally contribute to the variability. The lightcurve is consistent with a two-peaked period ∼8.26 hr but the period is non-unique as a result of aliasing in the data. Except for its unusually elongated shape, 1I/2017 U1 is a physically unremarkable, sub-kilometer, slightly red, rotating object from another planetary system. The steady-state population of similar, ∼100 m scale interstellar objects inside the orbit of Neptune is ∼10^4, each with a residence time ∼10 yr.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/16/2017 02:25 AM
Weird. Surely this would be a binary? A ratio of 6.9 would be like a skinny finger.
I'm not sure a binary helps much, naively two roughly spherical components of similar composition only gives you the equivalent of 2. You have a binary with elongated components, or a contact binary with a large "bridge" of loose material, but that's still pretty weird.

The authors suggest it could have been distorted by spin or close encounters in the parent system, but those processes should apply to solar system bodies too, so it's not obvious to me those explanations make it much less of an outlier.

They conclude albedo differences are unlikely to explain it, because the colors don't seem to vary, though the paper Mongo62 just posted suggests it could be a combination.

Looking back at the Knight et al DCT paper (https://arxiv.org/abs/1711.01402), they gave ~3 as a lower limit, because they didn't sample enough of the curve to say more.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/16/2017 03:57 AM
Weird. Surely this would be a binary? A ratio of 6.9 would be like a skinny finger.
I'm not sure a binary helps much, naively two roughly spherical components of similar composition only gives you the equivalent of 2. You have a binary with elongated components, or a contact binary with a large "bridge" of loose material, but that's still pretty weird.
Thanks. I hadn't realised that. How about a crater or hard edged facet?

This link says "comparable to the most elongated Solar System objects" implying it is not unheard of. Have we imaged anything like that?
https://en.wikipedia.org/wiki/1I/%CA%BBOumuamua
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/16/2017 05:15 AM
How about a crater or hard edged facet?
Without trying to analyze specific shapes, it seems safe to assume you can get extreme light curves with the right combination of shape and surface properties. IMO the weirdness isn't that you can't make a rock do this, it's that the first interstellar rock we see also happens to be at the extreme.
Quote
This link says "comparable to the most elongated Solar System objects" implying it is not unheard of. Have we imaged anything like that?
https://en.wikipedia.org/wiki/1I/%CA%BBOumuamua
I don't know. The Jewitt et al paper Mongo62 posted today says
Quote
However, we note that the 5 km diameter asteroid 4116 (Elachi) shows a range of 1.6 magnitudes (b/a = 4.3:1) that is almost as large (Warner and Harris 2011).
I would expect this was the most extreme example they knew of and felt was reliable. Notably, it's a much larger object. You might expect small objects to be able to have more extreme shapes, since they are less affected by self gravity.

It's also important to remember that the ratio inferred from a light curve gives a lower limit, because it depends on the viewing geometry. In the extreme example of the pole is facing you at 0 phase angle (sun behind you), the light curve would be flat regardless of the shape.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/17/2017 01:13 AM
Is 1I/2017 U1 really of interstellar origin? (https://arxiv.org/abs/1711.05735)

Here we investigate the possibility that the asteroid 1I/2017 U1 actually is a Solar System object, currently expelled from the Solar System by the recent encouter with a Solar System planet. We show that this possibility is extremely unlikeley and that 1I/2017 U1 really is an interstellar object.

Col-OSSOS: Colors of the Interstellar Planetesimal 1I/2017 U1 in Context with the Solar System (https://arxiv.org/abs/1711.06214)

The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound and hyperbolic orbit, offers a rare opportunity to explore the planetary formation processes of other stars, and the effect of the interstellar environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the inner Solar System in 2017 October was a unique chance to make observations matching those used to characterize the small-body populations of our own Solar System. We present near-simultaneous g′, r′, and J photometry and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gemini North Telescope, and gri photometry from the 4.2 m William Herschel Telescope. Our g′r′J observations are directly comparable to those from the high-precision Colours of the Outer Solar System Origins Survey (Col-OSSOS), and offer unique diagnostic information for distinguishing between outer Solar System surfaces. Substantial, correlated near-infrared and optical variability is present, with the same trend in both near-infrared and optical. Our observations confirm that 1I/`Oumuamua rotates with a double-peaked period of 8.10±0.42 hours and is a highly elongated body with an axial ratio of at least 5.3:1, implying that it has significant internal cohesion. 1I/`Oumuamua's color is at the neutral end of the range of observed g−r and r−J solar-reflectance colors, relative to asteroids, more distant minor planets, and to the trans-Neptunian populations measured by Col-OSSOS. The color of the first interstellar planetesimal is like the colors of the Solar System, in particular some of the dynamically excited objects of the Kuiper belt and the less-red Jupiter Trojans.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/17/2017 03:02 AM
Col-OSSOS: Colors of the Interstellar Planetesimal 1I/2017 U1 in Context with the Solar System (https://arxiv.org/abs/1711.06214)
They touch on the earlier question of how rare such elongated objects are:
Quote
Small asteroids with 1I/‘Oumuamua’s degree of elongation are rare but not unknown; examples include the ~ 200-300 m diameter Near-Earth Asteroids 2001 FE90 and 2007 MK13, both with lightcurve amplitudes ≥ 2.1 magnitudes
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: plutogno on 11/18/2017 07:20 AM
Is 1I/2017 U1 really of interstellar origin? (https://arxiv.org/abs/1711.05735)

from this paper:

Quote
up to now no outer Solar Solar system asteroid has never been detected, contrary to comets which are very common

as far as I know, a few Oort cloud asteroids have been detected. see for example https://en.wikipedia.org/wiki/2005_VX3 and https://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_greatest_aphelion#TNOs_with_an_aphelion_larger_than_200_AU
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ugordan on 11/18/2017 09:04 AM
Is 1I/2017 U1 really of interstellar origin? (https://arxiv.org/abs/1711.05735)

Here we investigate the possibility that the asteroid 1I/2017 U1 actually is a Solar System object, currently expelled from the Solar System by the recent encouter with a Solar System planet. We show that this possibility is extremely unlikeley and that 1I/2017 U1 really is an interstellar object.

This talks about the chances of it passing near the hypothetical Planet 9. Even if it did, how would that explain the 26 km/s of heliocentric boost when the orbital velocities hundreds of AU from the Sun are mere fractions of that.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/20/2017 01:14 AM
On the dynamical history of the recently discovered interstellar object A/2017 U1 - where does it come from? (https://arxiv.org/abs/1711.06618)

A/2017 U1 is the first interstellar object recorded inside the Solar System. We try to answer the obtrusive question: where does it come from? After a careful search in the close vicinity of the Sun we looked a bit further. Finally, we have checked over 200 thousand stars and found just a handful of candidates. If we limit our investigation to the Sun surroundings within about 30 pc, the most probable candidate for the A/2017 U1 parent stellar habitat is a star UCAC4 535-065571 but GJ 876 cannot be completely ruled out. However, the origin of A/2017 U1 from a more distant source is still an open question.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/20/2017 05:59 AM
Is 1I/2017 U1 really of interstellar origin? (https://arxiv.org/abs/1711.05735)

from this paper:

Quote
up to now no outer Solar Solar system asteroid has never been detected, contrary to comets which are very common

as far as I know, a few Oort cloud asteroids have been detected. see for example https://en.wikipedia.org/wiki/2005_VX3 and https://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_greatest_aphelion#TNOs_with_an_aphelion_larger_than_200_AU

Asteroid in this context means a rocky, ice-free body (i.e., which would not produce a tail when doing a fly-by of the sun). The densities of TNOs suggest that at least most of them have a contribution of ice which is substantial enough to affect their density. The ecliptic, long-period comets are likely derived from the TNOs, and they do form a tail.

1I/2017 U1 seems to have a color similar to P/D-type asteroids in the solar system, which are common in the outer asteroid belt and among trojans. While they might be water-rich (as in hydrated minerals which can also be identified in the spectrum), they are not in general thought to have substantial contributions from water ice.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/20/2017 06:27 AM
The ecliptic, long-period comets are likely derived from the TNOs, and they do form a tail.
A few rocky (edit: or no/extremely low activity) apparent Oort cloud bodies have been seen, e.g. 1996 PW and C/2014 S3 (PANSTARRS) (http://www.ifa.hawaii.edu/info/press-releases/manx_comets/) (though the later did show some activity)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Phil Stooke on 11/20/2017 07:15 AM
"The Oort Cloud is still a theory without proof.  Still seems implausible to me that our oceans were formed by it. "

You might be thinking about this the wrong way.  Not that the oceans came from the Oort cloud... but that many icy objects were scattered by the giant planets: those scattered outwards form the Oort cloud.  Those scattered inwards either fall into the Sun, or hit a planet (thereby delivering a bit of ocean), or get another gravity assist which flings them back out.  Still lots of nuances to figure out, isotopes etc., so the story can be refined.  But you are not really bringing an ocean in from the Oort cloud.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/20/2017 05:31 PM
https://www.nature.com/articles/nature25020

Quote
A brief visit from a red and extremely elongated interstellar asteroid

None of the approximately 750,000 known asteroids and comets is thought to have originated outside our Solar System, but formation models suggest that orbital migration of the giant planets ejected a large fraction of the original planetesimals into interstellar space1. The predicted interstellar number density2 of icy interstellar objects of 2.4 × 10−4 au−3 suggested that these should have been detected by surveys, yet hitherto none had been seen. Many decades of asteroid and comet characterization have yielded formation models that explain the mass distribution, chemical abundances and planetary configuration of today’s Solar System, but until now there has been no way to tell if our Solar System is typical. Here we report observations and subsequent analysis of 1I/2017 U1 (‘Oumuamua) that demonstrate the extrasolar trajectory of ‘Oumuamua. Our observations reveal the object to be asteroidal, with no hint of cometary activity despite an approach within 0.25 au of the Sun. Spectroscopic measurements show that the object’s surface is consistent with comets or organic-rich asteroid surfaces found in our own Solar System. Light-curve observations indicate that the object has an extreme oblong shape, with a 10:1 axis ratio and a mean radius of 102±4 m, assuming an albedo of 0.04. Very few objects in our Solar System have such an extreme light curve. The presence of ‘Oumuamua suggests that previous estimates of the density of interstellar objects were pessimistically low. Imminent upgrades to contemporary asteroid survey instruments and improved data processing techniques are likely to produce more interstellar objects in the upcoming years.

10:1! That's even more extreme than the first estimates... That elongated cylinderoid shape will have the web go crazy... perhaps we should have sticked to "Rama" for the name! :)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: redliox on 11/20/2017 06:27 PM
https://www.nature.com/articles/nature25020

Quote
A brief visit from a red and extremely elongated interstellar asteroid

None of the approximately 750,000 known asteroids and comets is thought to have originated outside our Solar System, but formation models suggest that orbital migration of the giant planets ejected a large fraction of the original planetesimals into interstellar space1. The predicted interstellar number density2 of icy interstellar objects of 2.4 × 10−4 au−3 suggested that these should have been detected by surveys, yet hitherto none had been seen. Many decades of asteroid and comet characterization have yielded formation models that explain the mass distribution, chemical abundances and planetary configuration of today’s Solar System, but until now there has been no way to tell if our Solar System is typical. Here we report observations and subsequent analysis of 1I/2017 U1 (‘Oumuamua) that demonstrate the extrasolar trajectory of ‘Oumuamua. Our observations reveal the object to be asteroidal, with no hint of cometary activity despite an approach within 0.25 au of the Sun. Spectroscopic measurements show that the object’s surface is consistent with comets or organic-rich asteroid surfaces found in our own Solar System. Light-curve observations indicate that the object has an extreme oblong shape, with a 10:1 axis ratio and a mean radius of 102±4 m, assuming an albedo of 0.04. Very few objects in our Solar System have such an extreme light curve. The presence of ‘Oumuamua suggests that previous estimates of the density of interstellar objects were pessimistically low. Imminent upgrades to contemporary asteroid survey instruments and improved data processing techniques are likely to produce more interstellar objects in the upcoming years.

10:1! That's even more extreme than the first estimates... That elongated cylinderoid shape will have the web go crazy... perhaps we should have sticked to "Rama" for the name! :)

I have to agree with that statement.  So far it apparently has a long shape, has no coma, and is solid like rock or metal.  It would be easy to presume it could be a spaceship.  However, it hasn't slowed down and is behaving like a rock from outer space.  It's intriguing enough that this is the first interstellar visitor, although if it were artificial it's acting either dead or passive...

If it were a passive observer (be it benign or covert invader), from its POV what views could it have had of our solar system during this visit?  Aside from the sun (in a vague sense), it didn't exactly fly by any of the planets akin to our probes...but still...what could it have noticed?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/20/2017 06:57 PM
Is 1I/2017 U1 Really of Interstellar Origin?

http://iopscience.iop.org/article/10.3847/2515-5172/aa9af2/meta
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Phil Stooke on 11/20/2017 07:10 PM
"a well defined region of the sky can be infrared from the analysis of the perturbations of Planet Nine "

Curse that autocorrect!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/20/2017 07:14 PM
@redilox: well if you are a space ship approaching a star system and don't want to draw any attention to yourself because you just realized there is a civilization on planet III, playing dead (or "asteroid") might well be your best option until you know more about their capabilities. I mean, if you were on an interstellar trajectory and had a fusion drive, you would definetely aim to pass close to the target star in order to do an Oberth burn to enter into stellar orbit...

But the surface does not seem to be metal or rock - instead, it looks like the organics-covered surfaces of D- and P-type asteroids in the solar system. That alone does not support such an extravagant hypothesis.

But the very oblong shape is strange.

@Star One: funny what passes for a scientific publication these days...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/20/2017 07:33 PM
ESO not helping things in their press release, just look at the image they’ve used or the headline.

Quote
ESO Observations Show First Interstellar Asteroid is Like Nothing Seen Before
VLT reveals dark, reddish and highly-elongated object

http://www.eso.org/public/news/eso1737/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/20/2017 07:35 PM
@redilox: well if you are a space ship approaching a star system and don't want to draw any attention to yourself because you just realized there is a civilization on planet III, playing dead (or "asteroid") might well be your best option until you know more about their capabilities. I mean, if you were on an interstellar trajectory and had a fusion drive, you would definetely aim to pass close to the target star in order to do an Oberth burn to enter into stellar orbit...

But the surface does not seem to be metal or rock - instead, it looks like the organics-covered surfaces of D- and P-type asteroids in the solar system. That alone does not support such an extravagant hypothesis.

But the very oblong shape is strange.

@Star One: funny what passes for a scientific publication these days...

Jason Wright’s response tweet about the article.

Quote
Jason Wright
@Astro_Wright
I don't think the conclusion here is correct.  I don't think *any* (bound) object could have scattered 1I into that orbit.  Orbital velocities out there are too low.

https://mobile.twitter.com/Astro_Wright/status/932686151412051968
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Blackstar on 11/20/2017 07:43 PM
I'm convinced:
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/20/2017 07:55 PM
JPL video complete with spooky electronic music.

https://www.youtube.com/watch?v=fbL1ZoAQgUU
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: gosnold on 11/20/2017 08:05 PM
I'm convinced:
I've got an an alternate theory:
(http://www.lichtschwerter.de/newsite/bilder/detail-high/props/falcon-front2.jpg)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/20/2017 08:19 PM
I'm convinced:
<cue spooky music>
(http://www.daviddarling.info/images/Doomsday_Machine.jpg)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/20/2017 08:23 PM
So let me get this straight the first interstellar object we detect just happens to look like Rama!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/20/2017 08:32 PM
ish.

Much smaller and clearly not as regular but with a very elongated profile. You can as easily compare it to a sausage :-)

The colour matches D asteroids pretty well

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/20/2017 08:40 PM
10:1! That's even more extreme than the first estimates... That elongated cylinderoid shape will have the web go crazy... perhaps we should have sticked to "Rama" for the name! :)
There's some disagreement between different groups about both the color and shape, I wouldn't put too much weight on the 10:1 over earlier estimates just yet.

For those without access, Nature paper is available from the ESO release https://www.eso.org/public/unitedkingdom/news/eso1737/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/20/2017 08:57 PM
A good discussion of colour from Meg Schwamb here https://twitter.com/megschwamb/status/932660021623644160 (https://twitter.com/megschwamb/status/932660021623644160)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Blackstar on 11/20/2017 09:18 PM
You can as easily compare it to a sausage :-)

I am a big fan of comparing planetary objects to breakfast foods. But it is not easy to do.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Helodriver on 11/20/2017 09:24 PM
I'm just glad that we still have Humpback whales in the ocean, and the ancient long thin large metallic interloper left us in peace because of it.


https://www.youtube.com/watch?v=U-fWlx5UhoM (https://www.youtube.com/watch?v=U-fWlx5UhoM)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/20/2017 09:25 PM
Maybe ages ago somebody out there in the universe spotted us on one of their habitable exoplanet surveys, and decided to send something our way.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: eeergo on 11/20/2017 09:25 PM
Interesting to note that the paper estimates at least one >250m diameter interstellar object present at <1 AU from the Sun *at any given time* (!!)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/20/2017 09:33 PM
ish.

Much smaller and clearly not as regular but with a very elongated profile. You can as easily compare it to a sausage :-)

The colour matches D asteroids pretty well

--- Tony

It also may have a high metal content, you can kind of see why its caught people’s attention.

By the way here’s Jim Oberg’s thoughts on the matter. He asks some interesting questions in this post.

Quote
This is basically one way 'first contact' might look. So it is truly exciting, and fun to enjoy the common well-deserved excitement.

One point -- nobody's keeping anything secret, apparently, although they could have. Unless there have been radio intercepts, or laser beam flashes. It might be prudent to broaden the observation instrumentation array just in case there were artificial signals that normal astronomical searching wouldn't look for.

Just in case.

How likely would it be that something randomly passing through the solar system would get so close to the sun?

OR -- are only those passers-by getting that close bright enough to be noticed by existing sky surveys?

To find the farther-out and dimmer ones, what wide-field search strategy would be productive, up to and including Hubble?

http://www.abovetopsecret.com/forum/thread1191385/pg2
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/20/2017 10:14 PM
While I doubt that this is anything more that just an asteroid, I would think that it likely has a very high metal content, as most asteroids in our solar system tend to be more rounded, without the high length h to width ratio that this seems to have.  Assuming a high iron content, I would not be entirely suprised if the reddish color is caused by atomic oxygen, oxidizing the surface over billions of years in interstellar space.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/20/2017 11:46 PM
It's being assumed that it's an asteroid - but how would they really be able to tell that it's something else? They don't seem to have actually imaged it, and they've only been able to vaguely determine its dimensions. It's assumed that the object is an asteroid, because that's what we expect it to be. It's ruled out from being a comet because there's no tail, etc.

If an artificially-made object of the same approximate dimensions were to pass through our solar system like this, then how would we really be able to tell that's it's not an asteroid? We'd need an actual image of it.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/21/2017 12:16 AM
Suppose it turns out that this shape is common for interstellar visitors. Can anyone think of a reason?

Perhaps some process like this could form a bridge, and perhaps it needs
(a) The harder cosmic radiation of interstellar space or
(b) A total lack of solar wind that would normally blow away the dust before it does something interesting.

Just throwing it out there, what about magnetised dust? We have all seen what magnets do to iron filings. Imagine spotting an asteroid sized version of that floating in space. I think it would throw the the media into a frenzy shouting aliens, but it would be a totally natural phenomenon.

Or how about this: A binary consisting of two asteroids with different composition. Wouldn't cosmic radiation tend to make a slightly different electric charge between them? This charge could pull dust to the pointiest point facing the other asteroid. Perhaps over eons you could get a sort of stalagmite-stalactite bridge growing between them.

(edit) or maybe you do not need a different charge. Maybe they build up the same charge, and dust is pulled to the pointiest point facing away from the other. So it might end up looking like two blades of a propeller with nothing connecting them.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/21/2017 12:59 AM
If an artificially-made object of the same approximate dimensions were to pass through our solar system like this, then how would we really be able to tell that's it's not an asteroid?  We'd need an actual image of it.
Imaging is totally out of the question for objects this size. If it had been spotted earlier, radar might have been possible.

A spectrum could strongly suggest one way or the other. Someone would probably notice if it was covered in gold foil or titanium dioxide paint. In this case, it appears consistent with some known solar system bodies, but being featureless it doesn't tell us definitively that it's made of the same stuff.

Also worth noting: The size estimates assume an albedo similar to the natural objects with similar colors. If our own spacecraft are anything to go by, an artificial object would likely be much more reflective, and correspondingly smaller. We might notice this in thermal IR, which is hopefully forthcoming from Spitzer. OTOH, who knows what a few million years of cosmic radiation does to paint and Kapton...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/21/2017 01:08 AM
Going with extreme suppositions;  What if it is a gigantic iron pyrite crystal?  In a magnitized environment, after a supernova, it could be possible, in microgravity, for truly  epic scale crystal to form.  At least in theory.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: matthewkantar on 11/21/2017 01:47 AM
As much as I love the idea of this being a mini Rama, this object is tumbling. so not likely a probe or passenger ship.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/21/2017 01:57 AM
As much as I love the idea of this being a mini Rama, this object is tumbling. so not likely a probe or passenger ship.

Even if it WERE some kind of mini Rama, millions, or perhaps billions of years in interstellar space, would probably be too much for even the most robust technologies.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/21/2017 05:47 AM
Where does the "high metal content" idea pushed by some in this thread come from (this is how rumors get started...)? There's no way we could tell given the observations so far. The elongated shape of the object certainly doesn't require it. D type asteroids are thought to be compositionally similar to CI chondrites like Orgueil or Ivuna (they have similar reflectance spectra): these are black, mostly featureless objects with no iron/nickel metal left (all oxidized, but total Fe content ~18%). Scroll down to Orgueil or Ivuna on this page to see a picture: http://www.psrd.hawaii.edu/July09/Meteorites.London.Museum.html

For color comparisons, see also this post by Michele Bannister: https://twitter.com/astrokiwi/status/931493521919545344

I guess it will be some time until the community finds a consistent light-curve-shape / rotation rate / body proportions model that everybody can agree with. Its just a pitty to see once more how the "publish or perish" culture leads to the publication of so many half-baked articles instead of a few, really good ones a few years down the road.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Zed_Noir on 11/21/2017 05:58 AM
If an artificially-made object of the same approximate dimensions were to pass through our solar system like this, then how would we really be able to tell that's it's not an asteroid?  We'd need an actual image of it.
Imaging is totally out of the question for objects this size. If it had been spotted earlier, radar might have been possible.

A spectrum could strongly suggest one way or the other. Someone would probably notice if it was covered in gold foil or titanium dioxide paint. In this case, it appears consistent with some known solar system bodies, but being featureless it doesn't tell us definitively that it's made of the same stuff.

Also worth noting: The size estimates assume an albedo similar to the natural objects with similar colors. If our own spacecraft are anything to go by, an artificial object would likely be much more reflective, and correspondingly smaller. We might notice this in thermal IR, which is hopefully forthcoming from Spitzer. OTOH, who knows what a few million years of cosmic radiation does to paint and Kapton...

For a covert system survey flyby. The intruder probe will most likely be clad in fake (or real) dull regolith to obscure the probe from being discovered by the system's natives as an artificial spacecraft instead of some random piece of space rock. One would think.  ;)

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 07:38 AM
If an artificially-made object of the same approximate dimensions were to pass through our solar system like this, then how would we really be able to tell that's it's not an asteroid?  We'd need an actual image of it.
Imaging is totally out of the question for objects this size. If it had been spotted earlier, radar might have been possible.

A spectrum could strongly suggest one way or the other. Someone would probably notice if it was covered in gold foil or titanium dioxide paint. In this case, it appears consistent with some known solar system bodies, but being featureless it doesn't tell us definitively that it's made of the same stuff.

Also worth noting: The size estimates assume an albedo similar to the natural objects with similar colors. If our own spacecraft are anything to go by, an artificial object would likely be much more reflective, and correspondingly smaller. We might notice this in thermal IR, which is hopefully forthcoming from Spitzer. OTOH, who knows what a few million years of cosmic radiation does to paint and Kapton...

For a covert system survey flyby. The intruder probe will most likely be clad in fake (or real) dull regolith to obscure the probe from being discovered by the system's natives as an artificial spacecraft instead of some random piece of space rock. One would think.  ;)

If it was a dead or inert probe I imagine it wouldn’t look that dissimilar to a natural object being just as likely to get covered in Tholins & tumbling along.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: TakeOff on 11/21/2017 07:57 AM
For how long will it be observable?
Has it or could it be observed by Hubble. And wouldn't JWST be helpful in infrared, but will it be operating in time?
Will it be possible to determine its shape much better?
As much as I love the idea of this being a mini Rama, this object is tumbling. so not likely a probe or passenger ship.

Even if it WERE some kind of mini Rama, millions, or perhaps billions of years in interstellar space, would probably be too much for even the most robust technologies.
Don't be too sure. Life has thrived on Earth for billions of years. Need not be different in a much smaller object, designed or not. Life's self-repair and evolution makes it pretty resilient. Infinite numbers of different life forms are possible, just from combinatorics of DNA on Earth.

We can only hope that they don't have a frame of reference that makes it look to them as if WE are attacking them with our Sun. ;-)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/21/2017 08:04 AM
Where does the "high metal content" idea pushed by some in this thread come from (this is how rumors get started...)?
I suspect it came from the ESO and NASA press releases, which both mentioned the possibility of a metallic composition. However, they don't suggest there is any evidence to favor this over stony composition.
ESO (https://www.eso.org/public/unitedkingdom/news/eso1737/)
Quote
These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

NASA (https://www.nasa.gov/feature/solar-system-s-first-interstellar-visitor-dazzles-scientists)
Quote
These properties suggest that ‘Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/21/2017 08:16 AM
For how long will it be observable?
Into early 2018, most likely.
Quote
Has it or could it be observed by Hubble.
Hubble observations started today: https://twitter.com/spacetelelive/status/932810823805874176
Quote
And wouldn't JWST be helpful in infrared, but will it be operating in time?
No chance for JWST. Spitzer will observe in IR.
Quote
Will it be possible to determine its shape much better?
Not much better. More light curve data will help some, color and spectroscopy may help disambiguate between color vs shape variations.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 08:16 AM
Where does the "high metal content" idea pushed by some in this thread come from (this is how rumors get started...)?
I suspect it came from the ESO and NASA press releases, which both mentioned the possibility of a metallic composition. However, they don't suggest there is any evidence to favor this over stony composition.
ESO (https://www.eso.org/public/unitedkingdom/news/eso1737/)
Quote
These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

NASA (https://www.nasa.gov/feature/solar-system-s-first-interstellar-visitor-dazzles-scientists)
Quote
These properties suggest that ‘Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.

Therefore it’s entirely justifiable to talk of a possible high metallic content.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/21/2017 08:19 AM
It also may have a high metal content, you can kind of see why its caught people’s attention.

By the way here’s Jim Oberg’s thoughts on the matter. He asks some interesting questions in this post.

Quote
This is basically one way 'first contact' might look. So it is truly exciting, and fun to enjoy the common well-deserved excitement.

One point -- nobody's keeping anything secret, apparently, although they could have. Unless there have been radio intercepts, or laser beam flashes. It might be prudent to broaden the observation instrumentation array just in case there were artificial signals that normal astronomical searching wouldn't look for.

Just in case.

How likely would it be that something randomly passing through the solar system would get so close to the sun?

OR -- are only those passers-by getting that close bright enough to be noticed by existing sky surveys?

To find the farther-out and dimmer ones, what wide-field search strategy would be productive, up to and including Hubble?

http://www.abovetopsecret.com/forum/thread1191385/pg2

First, on the high metal content, this appears to be driven by arguments about its strength: because it is tumbling quite fast, normal "contact binary" type asteroids would break apart so it must be reasonable strong.

However, a stony composition would also fit, and both are consistent with it being an elongated molten object ejected by a violent event.

On Oberg's questions, the reason we could find it at all is that is was close to the sun; we wouldn't have seen it otherwise.

On future prospects, the LSST is the best chance and I've seen estimates of it finding ~1 per year.

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: RotoSequence on 11/21/2017 10:01 AM
ish.

Much smaller and clearly not as regular but with a very elongated profile. You can as easily compare it to a sausage :-)

The colour matches D asteroids pretty well

--- Tony

The albedo of the rotating object suggests the presence of large, flat surfaces that can't be explained on a cylindrical object without non-uniform coloration - and uniform coloration has already been confirmed.  :o
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/21/2017 10:14 AM
Where does the "high metal content" idea pushed by some in this thread come from (this is how rumors get started...)?
I suspect it came from the ESO and NASA press releases, which both mentioned the possibility of a metallic composition. However, they don't suggest there is any evidence to favor this over stony composition.
ESO (https://www.eso.org/public/unitedkingdom/news/eso1737/)
Quote
These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

NASA (https://www.nasa.gov/feature/solar-system-s-first-interstellar-visitor-dazzles-scientists)
Quote
These properties suggest that ‘Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.

Therefore it’s entirely justifiable to talk of a possible high metallic content.

Nope. Just a case of "might contain peanuts". Doesn't mean it does. The point of distinction is between an ice-rich object and one made of refractory materials, the latter potentially including silicates, oxides, and metal. In particular, talking of a "high" metal content is a false claim. Don't do that.

For all we know, it could be made of cheese.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/21/2017 10:25 AM
The albedo of the rotating object suggests the presence of large, flat surfaces that can't be explained on a cylindrical object without non-uniform coloration - and uniform coloration has already been confirmed.  :o

I don't think there is evidence for either of those assertions, certainly not for the colour as there are significant (>3-sigma) differences between the various colour measurements published so far, a number of unpublished datasets, and known difficulties with calibration.

E.g. in Meech et al, there are large time differences between different wavelength measurements.  For a rotating body, this means you can only determine the colour is if you assume a uniform colour.  This is vastly different from confirmation of uniformity.

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/21/2017 10:52 AM
The only reason that I even suggested that the asteroid might have a high metal content is due to it's unusual shape.  Typical asteroids in our solar system tend to be more rounded, rather than long and angular.  Gravity tends to cause this in most cases.

   As this seems to be a singular solid mass, I was suggesting that the asteroid likely was more of an iron nickel structure, rather than a carbon or silicon based structure.  Any other types of nonterrestrial or extra solar artificial structures were inferred by others and not myself.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: RotoSequence on 11/21/2017 10:55 AM
The elongated shape and rotation seem indicative that the object has a modest amount of tensile strength to keep it in one piece. Meech et al suggests 3 Pascals is the minimum sufficient amount.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/21/2017 11:27 AM
If an artificially-made object of the same approximate dimensions were to pass through our solar system like this, then how would we really be able to tell that's it's not an asteroid?  We'd need an actual image of it.
Imaging is totally out of the question for objects this size. If it had been spotted earlier, radar might have been possible.

A spectrum could strongly suggest one way or the other. Someone would probably notice if it was covered in gold foil or titanium dioxide paint. In this case, it appears consistent with some known solar system bodies, but being featureless it doesn't tell us definitively that it's made of the same stuff.

Also worth noting: The size estimates assume an albedo similar to the natural objects with similar colors. If our own spacecraft are anything to go by, an artificial object would likely be much more reflective, and correspondingly smaller. We might notice this in thermal IR, which is hopefully forthcoming from Spitzer. OTOH, who knows what a few million years of cosmic radiation does to paint and Kapton...

Shouldn't some specific protocol be created to quickly and efficiently respond, if an event like this were to happen again in the future?

If another Interstellar object comes through our solar system again, then wouldn't it benefit us to detect it at the earliest, and then start taking detailed measurements of it as soon as possible? The data could provide valuable insights on the universe beyond our solar system.

In a perfect world, what would have been the ideal ways to respond to this event?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: LouScheffer on 11/21/2017 03:18 PM
Imaging is totally out of the question for objects this size. If it had been spotted earlier, radar might have been possible
Existing radars could get echos, but not detailed images, at this size and range.

From Astronomers Spot First-Known Interstellar “Comet” (http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/), the closest distance to Earth was 24,000,000 km, or about 0.16 AU. From this chart of the sensitivity of the Arecibo radar (https://echo.jpl.nasa.gov/~lance/snr/far_asnr18.gif), for an object this size and range, and an assumed radar albedo of 10%, the signal-to-noise ratio would be about 10.  SNR very roughly translates into pixels on target, so we'd expect about 10 pixel resolution.  Enough to tell if it's really elongated, but not enough to detect any surface features.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 04:39 PM
Where does the "high metal content" idea pushed by some in this thread come from (this is how rumors get started...)?
I suspect it came from the ESO and NASA press releases, which both mentioned the possibility of a metallic composition. However, they don't suggest there is any evidence to favor this over stony composition.
ESO (https://www.eso.org/public/unitedkingdom/news/eso1737/)
Quote
These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

NASA (https://www.nasa.gov/feature/solar-system-s-first-interstellar-visitor-dazzles-scientists)
Quote
These properties suggest that ‘Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.

Therefore it’s entirely justifiable to talk of a possible high metallic content.

Nope. Just a case of "might contain peanuts". Doesn't mean it does. The point of distinction is between an ice-rich object and one made of refractory materials, the latter potentially including silicates, oxides, and metal. In particular, talking of a "high" metal content is a false claim. Don't do that.

For all we know, it could be made of cheese.

And you seem to be engaged in what could be seen as a case of semantically dancing on the head of a pin. I am sure many politicians would be proud of that kind of response.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 07:24 PM
Quote
Eric Mamajek
@EricMamajek
Wet blanket for thoughts ‘Oumuamua might be artificial: it had the most boring, slow inbound velocity. W/r to Galactic circular velocity, solar system ran into it like a piece of driftwood. If it was artificial, you’d think someone would make an interstellar probe, uh, fast?

https://mobile.twitter.com/EricMamajek/status/933027160754753536
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Cherokee43v6 on 11/21/2017 07:49 PM
I'm convinced:

Actually Blackstar... I'm more thinking along the lines of a Zentradi Warship from Robotech/Macross. :)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/21/2017 07:57 PM
The only reason that I even suggested that the asteroid might have a high metal content is due to it's unusual shape.  Typical asteroids in our solar system tend to be more rounded, rather than long and angular.
While "rubble piles" are common, small asteroids that appear to be individual, cohesive fragments are known. Rocks can do this just as well as metal. X type is within the error bars of the colors in Bannister's paper, so yeah, it could be metallic, but it could be a lot of other stuff too.

Some people (not you) seem to want jump from "could be metallic composition" to "metallic = probably a spaceship!" which isn't really suggested by any of the available data  :P

edit:
To be clear, I'm saying the current data does not suggest an artificial origin. I'm not claiming that an artificial origin has been ruled out, in reality it's unlikely we will ever be able to do that definitively.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: whitelancer64 on 11/21/2017 08:15 PM
If an artificially-made object of the same approximate dimensions were to pass through our solar system like this, then how would we really be able to tell that's it's not an asteroid?  We'd need an actual image of it.
Imaging is totally out of the question for objects this size. If it had been spotted earlier, radar might have been possible.

A spectrum could strongly suggest one way or the other. Someone would probably notice if it was covered in gold foil or titanium dioxide paint. In this case, it appears consistent with some known solar system bodies, but being featureless it doesn't tell us definitively that it's made of the same stuff.

Also worth noting: The size estimates assume an albedo similar to the natural objects with similar colors. If our own spacecraft are anything to go by, an artificial object would likely be much more reflective, and correspondingly smaller. We might notice this in thermal IR, which is hopefully forthcoming from Spitzer. OTOH, who knows what a few million years of cosmic radiation does to paint and Kapton...

Shouldn't some specific protocol be created to quickly and efficiently respond, if an event like this were to happen again in the future?

If another Interstellar object comes through our solar system again, then wouldn't it benefit us to detect it at the earliest, and then start taking detailed measurements of it as soon as possible? The data could provide valuable insights on the universe beyond our solar system.

In a perfect world, what would have been the ideal ways to respond to this event?

"Ideal" would be more or less exactly what happened. As soon as the unusual nature of the object was known, astronomers around the world swarmed to observe it. Time on large observatories was granted ahead of requests made months ago due to the body's transience. No special coordination is really needed for something like this, since astronomers everywhere wanted to observe it anyway.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Blackstar on 11/21/2017 08:18 PM
Image has been updated:
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 08:23 PM
The only reason that I even suggested that the asteroid might have a high metal content is due to it's unusual shape.  Typical asteroids in our solar system tend to be more rounded, rather than long and angular.
While "rubble piles" are common, small asteroids that appear to be individual, cohesive fragments are known. Rocks can do this just as well as metal. X type is within the error bars of the colors in Bannister's paper, so yeah, it could be metallic, but it could be a lot of other stuff too.

Some people (not you) seem to want jump from "could be metallic composition" to "metallic = probably a spaceship!" which isn't really suggested by any of the available data 

Your second paragraph is unsupportable at this early stage. Unless you’re suggesting you’ve been out to look at it.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 08:25 PM
https://www.youtube.com/watch?v=NoVZNKTK_jA
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Thorny on 11/21/2017 08:29 PM
Image has been updated:
That looks so much like "The Doomsday Machine", Trekkies are gonna have a field day.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/21/2017 08:36 PM
Image has been updated:
That looks so much like "The Doomsday Machine", Trekkies are gonna have a field day.
It wouldn't be out of place in a Cheech and Chong movie, either.  8)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/21/2017 08:39 PM
Shouldn't some specific protocol be created to quickly and efficiently respond, if an event like this were to happen again in the future?
There is: Interesting objects get an MPEC (https://www.minorplanetcenter.net/mpec/K17/K17UI1.html)  and then every astronomer on twitter points whatever they've got (https://twitter.com/JoeMasiero/status/923062256874676224) at it ;)

More seriously, the NEO and transient astronomy (supernova, GRB etc) communities already have procedures established for rapid follow up. If you look at the papers that have already come out, a good fraction of the largest telescopes on Earth were looking at this thing within days of it being recognized as clearly interstellar. Directors discretionary time was also awarded quickly on Hubble and Spitzer.

It's also important to keep in mind is that it takes time to confirm that an object is actually interesting. If everyone dropped what they were doing when preliminary data looked a bit funny, nobody would get much done.
Quote
If another Interstellar object comes through our solar system again, then wouldn't it benefit us to detect it at the earliest, and then start taking detailed measurements of it as soon as possible? The data could provide valuable insights on the universe beyond our solar system.
Absolutely, but it's not clear to me there were major shortcomings this time around.

One thing I have seen mentioned is that the existing NEO detection pipelines aren't optimal for detecting objects like this, so it's possible software improvements could help us find more.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/21/2017 11:06 PM
Quote
Jason Wright
@Astro_Wright
Replying to @davidwhogg
The paper I am considering is a short research note discussing the (im)possibility is was scattered in from the Oort Cloud by a distant planet.

Why is it *likely* artificial?!? It’s low on my list of potentially artificial anomalies.

https://mobile.twitter.com/Astro_Wright/status/933096998072344576
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/21/2017 11:23 PM
Image has been updated:

Ok, is that an actual update, (highly unlikely) or some Photoshopped image? (Likely)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/22/2017 01:08 AM
1I/2017 U1 (Oumuamua) Might Be A Cometary Nucleus (https://arxiv.org/abs/1711.07535)

Since the photometry has not been able to detect a coma or a tail, the current consensus is that we are in the presence of an asteroid, whose colors are comparable to those of excited objects of the Kuiper belt or less-red Jupiter Trojans (Bannister et al., 2017), consistent with Kuiper belt colors (Masiero, 2017), colors overlapping the mean colors of D-type Trojan asteroids and other inner solar system populations, and inconsistent with the ultra-red matter found in the Kuiper belt (Jewitt et al., 2017).

In this work we find evidence that the object is of cometary origin.

[...]

The diagrams shows that colors of cometary nuclei fall inside an irregular ellipsoid, but 70% of them fall on a tilted line that we call *the main sequence of cometary nuclei colors*, MS. Plotting the above three observed colors of 1I/2017 U1 on the diagrams shows that the values lie on the MS. This suggests that 1I/2017 U1 is a cometary nucleus.

The next question is if this is an active or an extinct cometary nucleus.

Deep imaging by Meech (2017) failed to show a coma, but we can not exclude the possibility that this was an active comet because there were no observations at or near perihelion (the object was discovered +39 days past perihelion). Some low level cometary nuclei have very short periods of activity. As an example 107P/Wilson-Harrington was active for only 35±5 days (Ferrín et al., 2017).

One implication of this result is that then we do not know from where the object came. It may have come from the inner planetary region, from a local main belt, from the nearby region of a local Jupiter or from the Oort cloud of the parent star.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Patchouli on 11/22/2017 01:33 AM
I'm convinced:

Actually Blackstar... I'm more thinking along the lines of a Zentradi Warship from Robotech/Macross. :)
Same here.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/22/2017 07:13 AM
XKCD nails it

https://xkcd.com/1919/ (https://xkcd.com/1919/)

So can we stop with the silly spacecraft

/killjoy

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/22/2017 07:28 AM
XKCD nails it

https://xkcd.com/1919/ (https://xkcd.com/1919/)

So can we stop with the silly spacecraft

/killjoy

--- Tony

And this paragraph seems just as applicable here as elsewhere.

Quote
Skepticism still rules the day when it comes to these headlines, and the events that spawn them. That’s the way it should be, because we’ve always found a more prosaic reason for whatever signal from space we’re talking about. But, being skeptical is a balancing act; it doesn’t mean being dismissive.

https://futurism.com/either-stars-are-strange-or-234-alien-species-are-trying-to-contact-us/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/22/2017 09:22 AM
So can we stop with the silly spacecraft
The clip above also estimates 10,000 such objects in the solar system at a given time, spending about 10 years passing through, meaning about 1000 new objects enter the solar system each year. So I guess we can also stop worrying too much about this one getting away from us.

Hey, how about this:

Unless Im confused, this is a different NON-interstellar example of a highly elongated asteroid that we have actually imaged.
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20280
(this might have been the one already mentioned, but this is the first time I saw the image)

Just looking at that, there must be a process that forms such shapes, and if someone could explain the process it might be obvious why the process would apply even more in interstellar space. (less solar wind? less nudging by passing gravitational fields?)

(edit -- added later)
This link has some possibly relevant speculation. I expect less erosion from grit in interstellar space:
https://www.space.com/5587-strange-asteroid-shapes-explained.html
But what changes the asteroids' shape? Gyula and his team have shown that asteroids change shape from elongated to roughly spherical due to being impacted during their lifetimes. They are like pebbles on the beach that become worn smooth over many years -- only in space, erosion is caused by small impacts as rocks knock into each other and chip pieces off.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/22/2017 09:48 AM
So can we stop with the silly spacecraft
The clip above also estimates 10,000 such objects in the solar system at a given time, spending about 10 years passing through, meaning about 1000 new objects enter the solar system each year. So I guess we can also stop worrying too much about this one getting away from us.

Hey, how about this:

Unless Im confused, this is a different NON-interstellar example of a highly elongated asteroid that we have actually imaged.
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20280
(this might have been the one already mentioned, but this is the first time I saw the image)

Just looking at that, there must be a process that forms such shapes, and if someone could explain the process it might be obvious why the process would apply even more in interstellar space. (less solar wind? less nudging by passing gravitational fields?)

Or it’s just a shattered shard off a much bigger object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/22/2017 09:51 AM
The clip above also estimates 10,000 such objects in the solar system at a given time, spending about 10 years passing through, meaning about 1000 new objects enter the solar system each year. So I guess we can also stop worrying too much about this one getting away from us.

Yup.  From how long it took to spot this current one with Pan-STARS, I've seen estimates (I'll see if I can dig it out) that this means we should detect about 1 a year with the LSST when it's available.
 
Quote
Unless Im confused, this is a different NON-interstellar example of a highly elongated asteroid that we have actually imaged.
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20280
(this might have been the one already mentioned, but this is the first time I saw the image)

Yes, that's an interesting one.

Quote
Just looking at that, there must be a process that forms such shapes, and if someone could explain the process it might be obvious why the process would apply even more in interstellar space. (less solar wind? less nudging by passing gravitational fields?)

I suspect there is more than one mechanism for forming elongated objects.  Solar system objects like 2003 SD220 (that you linked), which are slow rotators (285 hours), can form relatively easily by slow speed collisions and they can be made of ice/rubble/etc.

However, 'Oumuamua rotates quickly (~8 hours), which requires structural strength (hence speculation about metallic composition; though rocky works just as well).

BTW, these things almost certainly *don't* form in interstellar space, but are ejected from systems as they are forming.  One of the speculations for 'Oumuamua is was formed from molten ejecta from an energetic planet/planet collision (there are others).

From the approach angle and velocity, it is was very travelling at close to the Galactic LSR (local system of rest; i.e. drifting around the galaxy) which probably means a distant origin (in time and distance).  [ This suggests to me that a fruitful way of finding these might be staring at the solar apex ]

Quote from: Star One
Or it’s just a shattered shard off a much bigger object.

I don't think a direct fragment is likely, but a heavily processed one (i.e. it melted) is possible

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/22/2017 10:45 AM
First data from Hubble can be found here https://archive.stsci.edu/proposal_search.php?id=15405&mission=hst (https://archive.stsci.edu/proposal_search.php?id=15405&mission=hst)

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/22/2017 10:55 AM
The clip above also estimates 10,000 such objects in the solar system at a given time, spending about 10 years passing through, meaning about 1000 new objects enter the solar system each year. So I guess we can also stop worrying too much about this one getting away from us.

Yup.  From how long it took to spot this current one with Pan-STARS, I've seen estimates (I'll see if I can dig it out) that this means we should detect about 1 a year with the LSST when it's available.
 
Quote
Unless Im confused, this is a different NON-interstellar example of a highly elongated asteroid that we have actually imaged.
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20280
(this might have been the one already mentioned, but this is the first time I saw the image)

Yes, that's an interesting one.

Quote
Just looking at that, there must be a process that forms such shapes, and if someone could explain the process it might be obvious why the process would apply even more in interstellar space. (less solar wind? less nudging by passing gravitational fields?)

I suspect there is more than one mechanism for forming elongated objects.  Solar system objects like 2003 SD220 (that you linked), which are slow rotators (285 hours), can form relatively easily by slow speed collisions and they can be made of ice/rubble/etc.

However, 'Oumuamua rotates quickly (~8 hours), which requires structural strength (hence speculation about metallic composition; though rocky works just as well).

BTW, these things almost certainly *don't* form in interstellar space, but are ejected from systems as they are forming.  One of the speculations for 'Oumuamua is was formed from molten ejecta from an energetic planet/planet collision (there are others).

From the approach angle and velocity, it is was very travelling at close to the Galactic LSR (local system of rest; i.e. drifting around the galaxy) which probably means a distant origin (in time and distance).  [ This suggests to me that a fruitful way of finding these might be staring at the solar apex ]

Quote from: Star One
Or it’s just a shattered shard off a much bigger object.

I don't think a direct fragment is likely, but a heavily processed one (i.e. it melted) is possible

--- Tony

Wouldn’t even a planetary collision struggle to impart sufficient energy to an object of this type for it achieve sufficient velocity to escape a planetary system.

We really need a telescope high above the plane of the solar system (and another below it) looking for objects coming in from the galactic centre. Being as the stellar density increases markedly in that direction I would expect a steady stream of flotsam and jetsam.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/22/2017 11:04 AM
Wouldn’t even a planetary collision struggle to impart sufficient energy to an object of this type for it achieve sufficient velocity to escape a planetary system.

Yes, but my point is that things ejected by such collisions would probably be melted, rather than being mere splinters of the original bodies.  And because they are molten, you can imagine tidal forces resulting in elongation.

Quote
We really need a telescope high above the plane of the solar system looking for objects coming in from the galactic centre. Being as the stellar density increases markedly in that direction I would expect a steady stream of flotsam and jetsam.

Unlikely.  Objects from the inner galaxy have a big gravitational hill to climb.  We are much more likely to find objects that share roughly the same orbit as the sun around the galaxy.  Such objects will most likely approach from roughly the solar apex (think Vega).

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 11/22/2017 11:04 AM
I'm convinced:

Personally, I think that it looks a lot like how I visualised Rama.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/22/2017 12:11 PM
Wouldn’t even a planetary collision struggle to impart sufficient energy to an object of this type for it achieve sufficient velocity to escape a planetary system.

Yes, but my point is that things ejected by such collisions would probably be melted, rather than being mere splinters of the original bodies.  And because they are molten, you can imagine tidal forces resulting in elongation.

Quote
We really need a telescope high above the plane of the solar system looking for objects coming in from the galactic centre. Being as the stellar density increases markedly in that direction I would expect a steady stream of flotsam and jetsam.

Unlikely.  Objects from the inner galaxy have a big gravitational hill to climb.  We are much more likely to find objects that share roughly the same orbit as the sun around the galaxy.  Such objects will most likely approach from roughly the solar apex (think Vega).

--- Tony

But as the Sun orbits the galactic centre it doesn’t stay static within the galactic plane but ‘bounces’ up and down so surely it will encounter things in different planes, some of these more favourable for material from the galactic centre I would have thought.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: TakeOff on 11/22/2017 01:42 PM
With all the binary stars around, there's alot more gravity power around than a fly by of a migrating Jupiter to get these things going all over the place. A comet/asteroid/whatever in a chaotic orbit might flyby both stars and get ejected, and dries out in a close encounter to never show a coma again. However, this one was pretty slow relative to the stellar neighborhood (of Vega) AFAIK.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/22/2017 02:29 PM

Yes, but my point is that things ejected by such collisions would probably be melted, rather than being mere splinters of the original bodies.  And because they are molten, you can imagine tidal forces resulting in elongation.

Why would tidal forces cause elongation? Wouldn't being molten tend to make things more spherical?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/22/2017 02:45 PM
1I/'Oumuamua is the first known definitely interstellar object to pass through the inner Solar System, but it won't be the last. The LSST is expected to find roughly one such object per year, and whatever follows that might find one or more such objects per month. Should there be a naming convention for these objects?

'Oumuamua is Hawaiian for "scout" or "first messenger", which is quite appropriate. I believe that future objects in the same category could be named after historic travelers or explorers, such as Ibm Battuta, Xuanzang and Pytheas, or for mythological adventurers.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/22/2017 04:20 PM
Why would tidal forces cause elongation? Wouldn't being molten tend to make things more spherical?

Consider a spinning, molten (but viscous) fragment passing a large body that ejects it from the system. At closest approach the side closest to the body is pulled more strongly than the side further away, stretching the fragment slightly. As the now oblate fragment gets further away, as it is still molten, the spin stretches it further and further until it solidifies.

Or something like that. Perhaps I should model it, but that's hard :)

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/22/2017 04:39 PM
`Oumuamua: Listening To An Interstellar Interloper

Quote
I contacted Jill Tarter and Andrew Siemion about whether SETI researchers are conducting observations of the interstellar interloper, Oumuamua. Both say yes.

Jill said that the Allen Telescope Array has been looking at it for a while. Andrew said that Breakthrough Listen was using the Green Bank Telescope for a few hours last weekend. This was actually looking for water via hydroxyl lines using broadband 1.1-1.9 GHz data. No water was immediately evident in the coarse spectra from the standard data reduction. Breakthrough Listen is working on incorporating the appropriate windowing capabilities necessary to analyze this data, so as to use their data analysis pipeline.

Therefore there are some observations in parts of the microwave spectrum.

https://www.centauri-dreams.org/?p=38844
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: TakeOff on 11/22/2017 05:43 PM
Is it possible that this object is not quite interstellar, but was slung here by a yet undiscovered large planet orbiting the Sun thousands of AU away? The hypothesized Planet Nine seems excluded because of the difference in inclination (30 and 120 degrees), but is a non-interstellar planetary gravity kick of an Oort Could object excluded by its trajectory and speed?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 11/22/2017 06:08 PM
No, the orbital speeds at those distances are not enough to give a big enough kick.

Gravity assists take energy from the orbital velocity and impart to to the object passing, but the orbital velocities out there are too low to account for all this objects energy.

This has been covered above.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/22/2017 07:13 PM
Fly-By of Interstellar Asteroid Portends Quadrillion Trillion More in Galaxy

Quote
Reports of the first-ever flyby of a body from another stellar system suggest a vast sea of interstellar shards and a Neptune-like planet around every star in the Milky Way

Quote
This vast sea of interstellar shards has some profound implications, as the ejection of debris from a newly forming planetary system is no easy task. Lofting an object like ‘Oumuamua free of its parent star requires the gravitational assistance of a planet that both has a substantial mass and is located at a fairly large radial distance. In our solar system, all four giant planets (and especially Jupiter and Neptune) are capable of slinging small bodies into interstellar space. The terrestrial planets, however, fall well short, as do the vast majority of the known extrasolar planets. If ‘Oumuamua-like objects abound, and if they are composed of icy outer-system material, then nearly every star in the galaxy must host a Neptune-like planet at a Neptune-like distance.
On the other hand, in the highly unlikely event ‘Oumuamua is indeed a refractory slab of rock or metal, as suggested by its complete lack of coma, then its appearance is extremely hard to understand. Only a few percent of stars host planets that are capable of ejecting volatile-free debris from warm regions deep within a gravitational well. They flat-out can’t generate the vast overall swarm implied by ‘Oumuamua’s recent passage, suggesting that another visit by a similar object won’t happen for a very long time.

https://blogs.scientificamerican.com/observations/fly-by-of-interstellar-asteroid-portends-quadrillion-trillion-more-in-galaxy/ (https://blogs.scientificamerican.com/observations/fly-by-of-interstellar-asteroid-portends-quadrillion-trillion-more-in-galaxy/)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/22/2017 08:57 PM
Why would tidal forces cause elongation? Wouldn't being molten tend to make things more spherical?

Consider a spinning, molten (but viscous) fragment passing a large body that ejects it from the system. At closest approach the side closest to the body is pulled more strongly than the side further away, stretching the fragment slightly. As the now oblate fragment gets further away, as it is still molten, the spin stretches it further and further until it solidifies.

Or something like that. Perhaps I should model it, but that's hard :)

--- Tony
Just wanted to add a laymans basic physics point: If an closed system cannot get rid of angular momentum by interacting with another system, it can't become spherical. At least not the entire thing. It would have to throw bits out to carry that momentum away or something. Just sum up all the angular momentums, cram it into a ball, and if the spin forces pushing it outward are 10x greater than the gravity forces then it wont happen.

I suspect these longish thin globules just turn out to be the natural solution of a certain high angular momentum system.

Anyway, I think the basic explanation is in here. Asteroids tend to form as elongated and become spherical over time from erosion that would not happen to the samples that were ejected early during the formation of a solar system.

(I posted this link above, but in an edit that may have been missed)
https://www.space.com/5587-strange-asteroid-shapes-explained.html
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/22/2017 09:44 PM
Yes, but my point is that things ejected by such collisions would probably be melted, rather than being mere splinters of the original bodies.
Ejecting something the size of ‘Oumuamua directly from a planetary impact may be hard, but it doesn't seem like a problem for small bodies. We see ‘Oumuamua sized blocks on small bodies (~300m boulders were seen on the surface of Lutetia for example), and we have seen small NEOs which appear to be monolithic.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/22/2017 09:57 PM
Quote from: Star One
Or it’s just a shattered shard off a much bigger object.

I don't think a direct fragment is likely, but a heavily processed one (i.e. it melted) is possible
Apart from conserving angular momentum, another place that physics creates long thin clumps is "Galactic filaments". Maybe you get the same structures forming in a cloud of magma after a major collision, cooling then breaking off shards.

This is all laymans speculation. I assume there is a lot of work in this area with lots of simulation.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/22/2017 11:43 PM
"Ideal" would be more or less exactly what happened. As soon as the unusual nature of the object was known, astronomers around the world swarmed to observe it. Time on large observatories was granted ahead of requests made months ago due to the body's transience. No special coordination is really needed for something like this, since astronomers everywhere wanted to observe it anyway.

Alright, but what if we also wanted to specifically determine if the object was natural or artificial? It doesn't seem like the measurements that have been taken would be able to conclusively tell us. So what would have to be done in order to tell us whether we're dealing with an artificial object versus a natural one?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/23/2017 03:07 AM
It doesn't seem like the measurements that have been taken would be able to conclusively tell us. So what would have to be done in order to tell us whether we're dealing with an artificial object versus a natural one?
IMO, for this to be answerable, you need to constrain what "unnatural" scenarios you want to be able to identify.

The observations taken or planned for this could certainly identify some scenarios, for example:
1) Astrometry would detect significant active maneuvering
2) Spectra would detect some artificial compositions, or at least identify them as unlike known solar system objects
3) Intentional radio or optical transmissions could be detected if they were strong enough (both GBT (https://dss.gb.nrao.edu/project/GBT17B-419/public) and the ATA have looked at microwave wavelengths)

The scenario left for the current object is a non-maneuvering artificial object with a nondescript asteroid-like spectrum and extreme but asteroid-compatible lightcurve. What capability would allow us to discriminate that from an actual asteroid?

For objects that aren't intentionally camouflaged, the obvious answer is a resolved image of at least a few hundred pixels square, but this is far beyond the capability of current telescopes. Detecting an object like this in time to build and launch something that can get close enough to take a picture is also far beyond current capability.

So without spending many gigabucks on new capabilities, we aren't likely to be able to definitively resolve cases like this.

If you do want to spend gigabucks, the most obvious path I see is to enhance detection capability to the point where you have enough advance notice to intercept with prebuilt flyby probes. This would be great science for natural objects, though for artificial one might worry that the difference between a scientific flyby probe and a missile is not obvious ;)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 11/23/2017 05:33 AM
@redilox: well if you are a space ship approaching a star system and don't want to draw any attention to yourself because you just realized there is a civilization on planet III, playing dead (or "asteroid") might well be your best option until you know more about their capabilities. I mean, if you were on an interstellar trajectory and had a fusion drive, you would definetely aim to pass close to the target star in order to do an Oberth burn to enter into stellar orbit...

But the surface does not seem to be metal or rock - instead, it looks like the organics-covered surfaces of D- and P-type asteroids in the solar system. That alone does not support such an extravagant hypothesis.

But the very oblong shape is strange.

@Star One: funny what passes for a scientific publication these days...

Jason Wright’s response tweet about the article.

Quote
Jason Wright
@Astro_Wright
I don't think the conclusion here is correct.  I don't think *any* (bound) object could have scattered 1I into that orbit.  Orbital velocities out there are too low.

https://mobile.twitter.com/Astro_Wright/status/932686151412051968

What about a moon of a planet out there?  That could be moving quite a bit faster.

Not that it seems likely, just not impossible.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/23/2017 06:28 AM
What about a moon of a planet out there?  That could be moving quite a bit faster.
Not that it seems likely, just not impossible.
Ha.. that reminds me of my totally hypothetical thread on stumbling across the missing mass in the form of improbably, stunningly, useful space slingshots of some type or other. Spinning Jupiter sized black holes or similar. It was just about speculating what could exist without being detected yet, with no need to justify why it should happen to turn out that way.

Imagine if we saw a rock shooting through our solar system at 1000kps, then a decade later we see another on a trajectory that intersected the first rock, and we just can't see anything out there where they intersected.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/23/2017 07:53 AM
It doesn't seem like the measurements that have been taken would be able to conclusively tell us. So what would have to be done in order to tell us whether we're dealing with an artificial object versus a natural one?
IMO, for this to be answerable, you need to constrain what "unnatural" scenarios you want to be able to identify.

The observations taken or planned for this could certainly identify some scenarios, for example:
1) Astrometry would detect significant active maneuvering
2) Spectra would detect some artificial compositions, or at least identify them as unlike known solar system objects
3) Intentional radio or optical transmissions could be detected if they were strong enough (both GBT (https://dss.gb.nrao.edu/project/GBT17B-419/public) and the ATA have looked at microwave wavelengths)

The scenario left for the current object is a non-maneuvering artificial object with a nondescript asteroid-like spectrum and extreme but asteroid-compatible lightcurve. What capability would allow us to discriminate that from an actual asteroid?

For objects that aren't intentionally camouflaged, the obvious answer is a resolved image of at least a few hundred pixels square, but this is far beyond the capability of current telescopes. Detecting an object like this in time to build and launch something that can get close enough to take a picture is also far beyond current capability.

So without spending many gigabucks on new capabilities, we aren't likely to be able to definitively resolve cases like this.

If you do want to spend gigabucks, the most obvious path I see is to enhance detection capability to the point where you have enough advance notice to intercept with prebuilt flyby probes. This would be great science for natural objects, though for artificial one might worry that the difference between a scientific flyby probe and a missile is not obvious ;)

In that article I posted yesterday one of the comments underneath suggested that the most sensible way of doing a probe would be to camouflage it. If the probe was passive and dropped off into the natural stream so to speak then there’s no way we could detect it. The way we broadcast stuff outwards you don’t need an active device and like a lot of our electronic intelligence gathering passive does the job.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/23/2017 08:21 AM
What about a moon of a planet out there?  That could be moving quite a bit faster.
To get ~26 km/s I think your moon needs to be > Neptune, in a close orbit around the primary. We'd probably notice if we had one of those in the outer solar system ;)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/23/2017 09:46 AM
Ejecting something the size of ‘Oumuamua directly from a planetary impact may be hard, but it doesn't seem like a problem for small bodies. We see ‘Oumuamua sized blocks on small bodies (~300m boulders were seen on the surface of Lutetia for example), and we have seen small NEOs which appear to be monolithic.

Agreed. Really, I was just playing around with ideas on how you could get very extended objects with enough tensile strength to spin in 8hrs (especially given the high density numbers from Bannister et al - 5.9g/cm^3 from memory).

--- Tony
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ben the Space Brit on 11/23/2017 10:05 AM
One interesting scenario for object ejection from a system that I saw once was a close encounter with a dense wandering object like a neutron star or white dwarf.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Johnnyhinbos on 11/23/2017 11:16 AM
So what gravity is generated at the poles of the object given its length and spin rate?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 11/23/2017 12:01 PM
Take a cylinder of half-height h, radius R, constant density p, and set up a cylindrical coordinate system with the z-axis parallel the axis of symmetry and 0 at the center. The on-axis gravitational potential is then as below where G is the gravitational constant.

PS google found this for me. I'll let you plug in the numbers
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: RonM on 11/23/2017 01:02 PM
So what gravity is generated at the poles of the object given its length and spin rate?

Using SpinCalc with 200 meter radius and one rotation every 7.3 hours yields about 0.0000012 g.

Need to spin it up to about 2 rpm to get 1 g.

http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/23/2017 05:13 PM
New article by Jason Wright.

Is 1I/’Oumuamua an Alien Spacecraft?

Quote
No, I don’t think there’s any reason to think it is, but there’s lots of chatter on Twitter that suggest astronomers think it could be:

Quote
That said, I’m glad that astronomers are, on the informal forum of Twitter anyway, having a SETI discussion about the prospect of discovering interstellar probes passing through the Solar System.  It’s a neat topic, and once worth thinking about.  I hope ‘Oumuamua inspires more real work on it in the peer-reviewed literature, including concrete suggestions of what to look for when future interstellar objects are discovered passing through.

http://sites.psu.edu/astrowright/2017/11/22/is-1ioumuamua-an-alien-spacecraft/

The first comment under the article is definitely worth a read.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/23/2017 06:51 PM
Really, I was just playing around with ideas on how you could get very extended objects with enough tensile strength to spin in 8hrs (especially given the high density numbers from Bannister et al - 5.9g/cm^3 from memory).
As I understand it, the densities discussed in these papers is the density required for it to hold together by self gravity alone, without any strength. From Bannister et al (https://arxiv.org/abs/1711.06214)
Quote
Such an ellipsoid spinning in P = 8.1 hours with a/b = 5.3 (Fig. 2) would require a density at least P = (a/b)2(3π)/(GP2) = 5.9 g.cm-3 to prevent it from shedding regolith, consistent with the observed absence of coma. If it is instead a contact binary of two prolate components, each with axes ratio 0.5(a/b) (to produce the same Δm) a similar density of 5.9 g.cm-3 is required to hold the components in mutual orbit. As these densities are unreasonably higher than those of likely compositions of silicate or icy materials, it requires that 1I/‘Oumuamua has internal strength.

If it has any strength, we know nothing of the density, and it doesn't actually need much cohesion to hold together, it just needs to be >0:
So what gravity is generated at the poles of the object given its length and spin rate?

Using SpinCalc with 200 meter radius and one rotation every 7.3 hours yields about 0.0000012 g.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/23/2017 10:05 PM
Nice article touching on the "aliens" question from Corey S. Powell
http://blogs.discovermagazine.com/outthere/2017/11/23/interstellar-asteroid-mystery/

It points to this reference for past spectral identification of artificial objects

Observations of J002E3: Possible Discovery of an Apollo Rocket Body (http://adsabs.harvard.edu/abs/2003DPS....35.3602J)
Quote
In early September 2002, spectral and photometric observations of J002E3 were made at IRTF and Mt. Biglow in an effort to determine whether the object was an asteroid or a human-made. Early observations yielded a possible spin-rate and orientation. Additional spectral observations were completed in May 2003 at the Air Force Maui Optical Supercomputing (AMOS) site. Through the modeling of common spacecraft materials, the observations of J002E3 show a strong correlation of absorption features to a combination of human-made materials including white paint, black paint, and aluminum. Absorption features in the near IR show a strong correlation with paint containing a titanium-oxide semiconductor. Using the material model and the orbital information, it was concluded that J002E3 is a human-made object from an Apollo rocket upperstage, most likely Apollo 12. In addition, the J002E3 observations were compared to spectral observations of other rocket bodies launched during a similar time and the results agree well. Results from the observations and modeling will be presented. This work has been a collaboration of governmental agencies, education institutions, and amateur astronomers. Funding agencies include National Research Council, NASA JSC, MIT, University of Arizona, and JPL.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 11/24/2017 08:37 AM
Nice article touching on the "aliens" question from Corey S. Powell
http://blogs.discovermagazine.com/outthere/2017/11/23/interstellar-asteroid-mystery/

It points to this reference for past spectral identification of artificial objects

Observations of J002E3: Possible Discovery of an Apollo Rocket Body (http://adsabs.harvard.edu/abs/2003DPS....35.3602J)
Quote
In early September 2002, spectral and photometric observations of J002E3 were made at IRTF and Mt. Biglow in an effort to determine whether the object was an asteroid or a human-made. Early observations yielded a possible spin-rate and orientation. Additional spectral observations were completed in May 2003 at the Air Force Maui Optical Supercomputing (AMOS) site. Through the modeling of common spacecraft materials, the observations of J002E3 show a strong correlation of absorption features to a combination of human-made materials including white paint, black paint, and aluminum. Absorption features in the near IR show a strong correlation with paint containing a titanium-oxide semiconductor. Using the material model and the orbital information, it was concluded that J002E3 is a human-made object from an Apollo rocket upperstage, most likely Apollo 12. In addition, the J002E3 observations were compared to spectral observations of other rocket bodies launched during a similar time and the results agree well. Results from the observations and modeling will be presented. This work has been a collaboration of governmental agencies, education institutions, and amateur astronomers. Funding agencies include National Research Council, NASA JSC, MIT, University of Arizona, and JPL.

It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: RotoSequence on 11/24/2017 08:53 AM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.

The hypothesis that it's artificial in nature doesn't have a lot to go by, aside from a very strange aspect ratio and a lot of wishful thinking.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 11/24/2017 09:21 AM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.

The hypothesis that it's artificial in nature doesn't have a lot to go by, aside from a very strange aspect ratio and a lot of wishful thinking.

Of course.  But that's irrelevant to my point.

Someone gave one particular reason to think it's natural.  I was pointing out that that one reason wasn't very compelling.  It doesn't mean there aren't other reasons that are compelling.

Even if you agree with a conclusion, it's only right to point out when one of the arguments is flawed.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/24/2017 09:35 AM
Nice article touching on the "aliens" question from Corey S. Powell
http://blogs.discovermagazine.com/outthere/2017/11/23/interstellar-asteroid-mystery/

It points to this reference for past spectral identification of artificial objects

Observations of J002E3: Possible Discovery of an Apollo Rocket Body (http://adsabs.harvard.edu/abs/2003DPS....35.3602J)
Quote
In early September 2002, spectral and photometric observations of J002E3 were made at IRTF and Mt. Biglow in an effort to determine whether the object was an asteroid or a human-made. Early observations yielded a possible spin-rate and orientation. Additional spectral observations were completed in May 2003 at the Air Force Maui Optical Supercomputing (AMOS) site. Through the modeling of common spacecraft materials, the observations of J002E3 show a strong correlation of absorption features to a combination of human-made materials including white paint, black paint, and aluminum. Absorption features in the near IR show a strong correlation with paint containing a titanium-oxide semiconductor. Using the material model and the orbital information, it was concluded that J002E3 is a human-made object from an Apollo rocket upperstage, most likely Apollo 12. In addition, the J002E3 observations were compared to spectral observations of other rocket bodies launched during a similar time and the results agree well. Results from the observations and modeling will be presented. This work has been a collaboration of governmental agencies, education institutions, and amateur astronomers. Funding agencies include National Research Council, NASA JSC, MIT, University of Arizona, and JPL.

It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.

Well said. Using human made objects as a baseline in this case seems a complete waste of time.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: RotoSequence on 11/24/2017 09:45 AM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.

The hypothesis that it's artificial in nature doesn't have a lot to go by, aside from a very strange aspect ratio and a lot of wishful thinking.

Of course.  But that's irrelevant to my point.

Someone gave one particular reason to think it's natural.  I was pointing out that that one reason wasn't very compelling.  It doesn't mean there aren't other reasons that are compelling.

Even if you agree with a conclusion, it's only right to point out when one of the arguments is flawed.

I must disagree to some extent. The argument "if they're aliens, we can't know what we're looking for" ascribes gaps in information or other missing pieces to a higher power (sufficiently advanced space-magic), which is a logical fallacy.

Still, I like entertaining the notion of aliens.  ;D

If the asteroid is in fact a ship, the detection of neutral coloration, similar to tholins, suggests active camouflage efforts or a buildup of interstellar debris over an extraordinary period of time. The former cannot be proven without active maneuvers or sending a probe to Oumuamua, while the latter needs a mathematical model to describe how tholins become tightly bound to the body of a ship, unperturbed by close passes to our sun. In addition, it would need to be determined if tholin buildup on a regular asteroid could be distinguished from tholin buildup on an artificial structure.

As an aside, the extraordinary shape of this object fits strangely with how utterly average its spectrum is for objects in the outer solar system; I would have expected its spectrum to reflect the processes that formed such an unusual shape to some extent.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: M.E.T. on 11/24/2017 11:04 AM
It seems a bit strange that the aliens would go to the effort of covering the surface of the ship to resemble an asteroid, and yet retain a very "un-asteroid" like shape, which is what drew our comparatively primitive species' attention in the first place, despite us having very limited ability to track and observe their interloper.

One would think that with only a little extra effort, they could have modified the shape to be nondescript as well.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/24/2017 11:38 AM
It seems a bit strange that the aliens would go to the effort of covering the surface of the ship to resemble an asteroid, and yet retain a very "un-asteroid" like shape, which is what drew our comparatively primitive species' attention in the first place, despite us having very limited ability to track and observe their interloper.

One would think that with only a little extra effort, they could have modified the shape to be nondescript as well.

How do you know that in their solar system that isn’t a normal shape for asteroids. They might have converted an existing natural object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: eeergo on 11/24/2017 11:51 AM
It seems a bit strange that the aliens would go to the effort of covering the surface of the ship to resemble an asteroid, and yet retain a very "un-asteroid" like shape, which is what drew our comparatively primitive species' attention in the first place, despite us having very limited ability to track and observe their interloper.

One would think that with only a little extra effort, they could have modified the shape to be nondescript as well.

How do you know that in their solar system that isn’t a normal shape for asteroids. They might have converted an existing natural object.

Occam's razor would suggest that, if that's a typical natural object in another system, it would be much more likely to have visited us as a natural phenomenon.

There's something that has always bugged me about this being an alien ship: why would they prefer a long shape over any other for a non-atmospheric ship? Ok, I get the O'Neill cylinder concept, but there are countless others with many morphologies... these "elongated shape = spaceship" are too (childishly, IMO) influenced by popular science fiction, and lack imagination -- when their proponents make it seem as if they are the one entertaining imaginative out-of-the-box ideas.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bynaus on 11/24/2017 12:19 PM
There's something that has always bugged me about this being an alien ship: why would they prefer a long shape over any other for a non-atmospheric ship? Ok, I get the O'Neill cylinder concept, but there are countless others with many morphologies... these "elongated shape = spaceship" are too (childishly, IMO) influenced by popular science fiction, and lack imagination -- when their proponents make it seem as if they are the one entertaining imaginative out-of-the-box ideas.

Well, it makes sense for a fast interstellar ship to expose only a small cross-section towards the direction of flight. I guess the best shape would be an elongated ellipsoid with an axis ratio proportional to the relativistic dilatation factor it can reach (so that the ship is an effective sphere at cruising speed). A 10:1 ratio would then correspond to a top velocity of 99.5% c. :)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: JasonAW3 on 11/24/2017 01:51 PM
Here's an ejection scenario that MIGHT explain the rather odd shape of this asteroid;

      The asteroid is the remnant of a rocky planet destroyed in a supernova.

      It occurs to me that many have described what would happen to a rocky planet hit by a suprnova's plasma wave front as being much like "a ice ball hit with a blow torch".

      Essentially; the planet is shattered and melted like being in a blast furnace.  As this would produce streamers and huge "droplets" of surface and subsurface materials, the object would likely take on an elongated form as it cooled, especially if it had a slow speed spin applied early on after the initial explosion.  Much like warm taffy being stretched as it cools.

      I would not be altogether surprised if we find that this asteroid has a higher density towards the ends of the object, rather than in the middle.

      Assuming that it is highly metallic as well, filaments of metal would also be stretched out through the structure of the asteroid, both keeping the asteroid from flying apart, as well as keeping it from collapsing into a more rounded shape.

      The tholins on the surface could have been generated by the mixed plasma in the supernova wave front.

      A nova, COULD produce similar effects, assuming the rocky planet in question is in fairly close orbit around its' primary star.

      Just a thought, but I suspect that this would be a good possibility.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Lumina on 11/24/2017 02:27 PM
It might've lost its volatiles billions of years ago before it was ejected from its (now long gone) binary star system of origin.

jebbo:
I think the point is that Jupiter couldn't have done it (alone) because they never get close.

Three unusual attributes of this space rock. Elongated, ejected from its home system and free of volatiles.

It's worth considering whether a single cause could explain all three.

For example, a small rocky exoplanet had a near-miss with a Jupiter-sized planet, then another near-miss with its home star, breaking up into splinters, one of which was sent our way. Small differences in direction and velocity at the point of origin would mean that this is all we'd get to see from such an event.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/24/2017 03:14 PM
I think we will find this shape is fairly common for asteroids that have just formed, and it is asteroids that are not ejected from their solar system that tend to get worn down into something more spherical over time.

https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20280
https://www.space.com/5587-strange-asteroid-shapes-explained.html

On the subject of aliens, I think what you do the usual scientific process of competing theories. Initially you are just looking for something which is unusual, which is actually discarding all the common natural phenomena candidates. If it looks common without an anomaly, sure it could still be aliens in disguise but you can't do much with that.

Once you have found something really anomalous you are still faced with the situation "Unspecified natural hypothesis beats unspecified alien hypothesis." IMO this means that to progress further you have to look at the anomaly and brainstorm an actual deeper explanation for it, with predictions that can be tested.

The anomaly might a lot of plutonium or other short lived element for example. It is not just that it is anomalous and that we have difficulty imagining the natural process that would gather plutonium, it is also that we can imagine uses for plutonium, such as a powerplant. Then you could strengthen that powerplant theory by finding products of fast fission instead of natural decay (or something like that, Im hazy on the specific products)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/24/2017 04:06 PM
I think that there has been a lot of unsupported speculation on this thread. What do we know for a fact about this object?

1. Definitely interstellar in origin, moving at close to the general velocity of gravitationally unbound objects in this part of the Galaxy.

2. There has been no obvious originating exoplanetary system found so far. There are a few possibilities, but all of them appear to have a low probability of being the originating system.

3. The reddish color slope of the object is consistent with an outer solar system object, either asteroidal or cometary. Its color is consistent with a variety of compositions, and in fact is exactly what would be expected for a dormant comet nucleus.

4. The shape derived from its light curve is highly unusual (but not unheard of) for a rocky asteroidal object, but comet nuclei have been found to frequently be quite elongated, although not as elongated as this object appears to be. A small sample size warning for comet nuclei, though.

5. Part of the light curve variations might be due to compositional differences, bringing its shape into the normal range.

6. Its rotation period of around 8 hours is not unusual, and is well over the limit for "rubble piles" of its size.

Conclusion: what we know of this object is consistent with a natural origin in the outer portions of an unidentified exoplanetary system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/24/2017 04:52 PM
As this article points out Oumuamua might be a rare type of interstellar natural visitor to our solar system. Perhaps all the more reason to chase after it with a probe.

https://www.centauri-dreams.org/?p=38854
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/24/2017 07:11 PM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.
The point of the J002E3 reference isn't that we could recognize all artificial objects spectroscopically, it's that "things that look like asteroids" are a narrow subset of possible compositions, and we have the capability to recognize things that are wildly different.

Even if we had never built a Saturn V, we would have recognized J002E3 as weird. We certainly shouldn't assume that aliens would use titanium dioxide paint (though if they need white, it's a pretty good choice...) but unless deliberate camouflage is involved, using something that was a dead ringer for natural solar system objects would be quite a coincidence.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 11/24/2017 07:29 PM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.

The hypothesis that it's artificial in nature doesn't have a lot to go by, aside from a very strange aspect ratio and a lot of wishful thinking.

Of course.  But that's irrelevant to my point.

Someone gave one particular reason to think it's natural.  I was pointing out that that one reason wasn't very compelling.  It doesn't mean there aren't other reasons that are compelling.

Even if you agree with a conclusion, it's only right to point out when one of the arguments is flawed.

I must disagree to some extent. The argument "if they're aliens, we can't know what we're looking for" ascribes gaps in information or other missing pieces to a higher power (sufficiently advanced space-magic), which is a logical fallacy.

That's not in any way the argument I, or anyone else on this thread, made.

What I'm saying is that if we're considering an artificial object made by aliens, the range of things we need to consider is significantly broader than the range of things we need to consider if we're considering an artificial object made by humans.

It's not that we can't know anything about what we're looking for -- it's that we know less than if we're looking for something we ourselves made.

Still, I like entertaining the notion of aliens.  ;D

If the asteroid is in fact a ship, the detection of neutral coloration, similar to tholins, suggests active camouflage efforts or a buildup of interstellar debris over an extraordinary period of time.

That's only one possible explanation.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: ChrisWilson68 on 11/24/2017 07:36 PM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.
The point of the J002E3 reference isn't that we could recognize all artificial objects spectroscopically, it's that "things that look like asteroids" are a narrow subset of possible compositions, and we have the capability to recognize things that are wildly different.

Even if we had never built a Saturn V, we would have recognized J002E3 as weird. We certainly shouldn't assume that aliens would use titanium dioxide paint (though if they need white, it's a pretty good choice...) but unless deliberate camouflage is involved, using something that was a dead ringer for natural solar system objects would be quite a coincidence.

I think "dead ringer for natural solar system objects" is overstating the case.

It's the equivalent of noticing that something floating on a river in the distance is green, then saying since lots of natural things in a forest are green, the floating object is a dead ringer for natural forest objects.  Yeah, it's consistent with natural forest objects, but "dead ringer" implies a much more tightly-constrained match than we have with just being green.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/25/2017 06:04 AM
It's considerably easier to distinguish human-made artificial from natural objects than it is to distinguish alien-made artificial from natural objects, because we know exactly how we made the artificial objects we have launched.
The point of the J002E3 reference isn't that we could recognize all artificial objects spectroscopically, it's that "things that look like asteroids" are a narrow subset of possible compositions, and we have the capability to recognize things that are wildly different.

Even if we had never built a Saturn V, we would have recognized J002E3 as weird. We certainly shouldn't assume that aliens would use titanium dioxide paint (though if they need white, it's a pretty good choice...) but unless deliberate camouflage is involved, using something that was a dead ringer for natural solar system objects would be quite a coincidence.

I think "dead ringer for natural solar system objects" is overstating the case.

It's the equivalent of noticing that something floating on a river in the distance is green, then saying since lots of natural things in a forest are green, the floating object is a dead ringer for natural forest objects.  Yeah, it's consistent with natural forest objects, but "dead ringer" implies a much more tightly-constrained match than we have with just being green.

Here's a different angle.

We've just gained the ability to detect and observe interstellar objects.  In a few years, we'll be able to observe a lot more.

There are supposed to be a large number of interstellar objects.

How did the aliens know, millions of years in advance, to a resolution of just a few years, when humanity will achieve this ability?

(Unless of course there alien objects scouting our solar system every year or two, for the last few million years, and said objects do not want to get captured and stay around)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: nacnud on 11/25/2017 09:01 AM
How did the aliens know, millions of years in advance, to a resolution of just a few years, when humanity will achieve this ability?

Why do you always find the thing you are looking for in the last place you look?

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/25/2017 12:12 PM
How did the aliens know, millions of years in advance, to a resolution of just a few years, when humanity will achieve this ability?

Why do you always find the thing you are looking for in the last place you look?
In the face of this, I submit.

Well played.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Johnnyhinbos on 11/25/2017 12:26 PM
For the sake of conversation, perhaps this could be a probe or spaceship, but just long dead - tumbling through the void for eons on end with nothing guiding it, nothing emitting from it - a dead hulk. Lord knows we’ve tossed our own (future) space junk into interstellar space...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/25/2017 05:16 PM
For the sake of conversation, perhaps this could be a probe or spaceship, but just long dead - tumbling through the void for eons on end with nothing guiding it, nothing emitting from it - a dead hulk. Lord knows we’ve tossed our own (future) space junk into interstellar space...
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/25/2017 07:44 PM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: KelvinZero on 11/25/2017 11:22 PM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/25/2017 11:57 PM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.

Maybe all those loose rocks constitute a single "mega-system", and our our solar system is actually the odd piece of debris drifting through theirs...

Mind...  blown.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Bob Shaw on 11/26/2017 12:26 AM
Go and read some of Ken McLeod's SF novels - he has conscious and highly logical cryogenic comets wandering around, and they disdain the irrational planetary intelligences...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/26/2017 01:12 AM
Go and read some of Ken McLeod's SF novels - he has conscious and highly logical cryogenic comets wandering around, and they disdain the irrational planetary intelligences...
Read "Spin" a while ago...

We should get back on topic b4 an interplanetary mod swings by.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Johnnyhinbos on 11/26/2017 02:34 AM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.
Have you read about the Carter Catastrophe? And related to that, the Copernican principal? It  doesn’t require millions of such encounters, it just requires the first...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/26/2017 03:44 AM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.
Have you read about the Carter Catastrophe? And related to that, the Copernican principal? It  doesn’t require millions of such encounters, it just requires the first...

Just looked it up...  I dunno...

The very assumption that births are random, or even that your position in the birth-line is random, is absurd. 

The process of the life of a civilization is not memoryless sequence of random events... it's all inter-dependent.  The odds of civilization enduring beyond N years is simply not a function of its past history.  It has to do with when they develop which technology, and when a GRB occurs in our galaxy, and one-off political events and wars and diseases and what not... 

All those considerations are lost in Carter's line of reasoning, like tears in rain.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/26/2017 04:52 AM


For the sake of conversation, perhaps this could be a probe or spaceship, but just long dead - tumbling through the void for eons on end with nothing guiding it, nothing emitting from it - a dead hulk. Lord knows we’ve tossed our own (future) space junk into interstellar space...
I would just suppose this is just a meaningless rock.

But ok. If one were to ascribe a meaningful purpose to it... it looks like the object just did a slingshot maneuver for a course correction. 

With this assumption, the top questions I'd have:
1) Is the object now going faster relative to the galactic coordinate system?  (obviously the relative speed inbound/outbound with the Sun is hyperbolic but about the same)
2) Maybe there is trace evidence of a powerful solar thermal based guidance system being used while it arrived at perihelion? (maybe it didn't originate from where we assume it did).
3) Does this object intersect with a known star system in 1000 or more years?
4) Is the object similar to any other observed objects known, or is it an intergalactic spacecraft as many ancient astronaut theorists believe?

Question #3 is definitely interesting!  :)

Question #1 less so, since a gravity assist can be used to speed up, slow down, or just steer.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: hop on 11/26/2017 08:11 PM
3) Does this object intersect with a known star system in 1000 or more years?
Certainly not on few thousand year timescales, since it couldn't even reach the nearest stars in that time. I think people have looked and found no close encounters in the foreseeable future, but the published papers about the trajectory all focus on the past.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/27/2017 01:03 AM
`Oumuamua as a messenger from the Local Association (https://arxiv.org/abs/1711.08800)

With a hyperbolic trajectory around the Sun, `Oumuamua is the first confirmed interstellar object. However, its origin is poorly known. By simulating the orbits of 0.23 million local stars, we find 109 encounters with periastron less than 5 pc. `Oumuamua's low peculiar velocity is suggestive of its origin from a young stellar association with similar velocity. In particular, we find that `Oumuamua would have had slow encounters with at least five young stars belonging to the Local Association thus suggesting these as plausible sites for formation and ejection. In addition to an extremely elongated shape, the available observational data for `Oumuamua indicates a red colour suggestive of a potentially organic-rich and activity-free surface. These characteristics seem consistent with formation through energetic collisions between planets and debris objects in the middle part of a young stellar system. We estimate an abundance of about 6.0×10^−3 au^−3 for such interstellar objects with mean diameter larger than 100 m and find that it is likely that most of them will be ejected into the Galactic halo. Our Bayesian analysis of the available light curves indicates a rotation period of 6.96+1.45−0.39 h which is consistent with the estimation by Meech et al. 2017 and shorter than other literature. The codes and results are available on GitHub.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/27/2017 04:03 AM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.

Just because one object looks like a UFO, doesn't mean all objects have to be UFOs.

But I've read sci-fi stories where an alien menace spreads across the galaxy like a virus - consuming some planet or even a star to replicate itself, and then bursting forth to spread to other star systems - like a virus does.

So if the universe is billions of years old, perhaps it's possible that some entity - maybe a machine swarm, if you will - could have evolved/emerged to spread that way.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/27/2017 04:15 AM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.

Just because one object looks like a UFO, doesn't mean all objects have to be UFOs.

But I've read sci-fi stories where an alien menace spreads across the galaxy like a virus - consuming some planet or even a star to replicate itself, and then bursting forth to spread to other star systems - like a virus does.

So if the universe is billions of years old, perhaps it's possible that some entity - maybe a machine swarm, if you will - could have evolved/emerged to spread that way.
Yup.  The only aliens hypothesis that gets around the "serendipity objection" is the supposition that we have been getting such visitors continuously, though of course the timespans involved are still incredibly long.

Frankly I'm amazed this object hasn't generated nearly a similar amount of paranoia as "planet X" did...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/27/2017 04:44 AM
Yup.  The only aliens hypothesis that gets around the "serendipity objection" is the supposition that we have been getting such visitors continuously, though of course the timespans involved are still incredibly long.

Frankly I'm amazed this object hasn't generated nearly a similar amount of paranoia as "planet X" did...

Well, at least we now know that comets aren't the only possibility for Pan-Spermia. It could be asteroids too.

I'm just wondering if most interstellar travelers have the same odd shape as this one, or if it was just mere happenstance that our first observed interstellar visitor happened to have this elongated type of shape.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: meekGee on 11/27/2017 04:48 AM
Yup.  The only aliens hypothesis that gets around the "serendipity objection" is the supposition that we have been getting such visitors continuously, though of course the timespans involved are still incredibly long.

Frankly I'm amazed this object hasn't generated nearly a similar amount of paranoia as "planet X" did...

Well, at least we now know that comets aren't the only possibiity for Pan-Spermia. It could be asteroids too.

I'm just wondering if most interstellar travelers have the same odd shape as this one, or if it was just mere happenstance that our first observed interstellar visitor happened to have this elongated type of shape.
Looking forward to finding out in the coming years
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: jebbo on 11/27/2017 06:54 AM
A short paper discussing possible origins for `Oumuamua.

It makes a reasonable argument for a young age and has a less extreme aspect ratio of 6:1.

Quote
With a hyperbolic trajectory around the Sun, `Oumuamua is the first confirmed interstellar object. However, its origin is poorly known. By simulating the orbits of 0.23 million local stars, we find 109 encounters with periastron less than 5 pc. `Oumuamua's low peculiar velocity is suggestive of its origin from a young stellar association with similar velocity. In particular, we find that `Oumuamua would have had slow encounters with at least five young stars belonging to the Local Association thus suggesting these as plausible sites for formation and ejection. In addition to an extremely elongated shape, the available observational data for `Oumuamua indicates a red colour suggestive of a potentially organic-rich and activity-free surface. These characteristics seem consistent with formation through energetic collisions between planets and debris objects in the middle part of a young stellar system. We estimate an abundance of about 6.0×10−3 au−3 for such interstellar objects with mean diameter larger than 100 m and find that it is likely that most of them will be ejected into the Galactic halo. Our Bayesian analysis of the available light curves indicates a rotation period of 6.96+1.45−0.39 h which is consistent with the estimation by Meech et al. 2017 and shorter than other literature. The codes and results are available on GitHub.

https://arxiv.org/abs/1711.08800 (https://arxiv.org/abs/1711.08800)

--- Tony
It's not aliens. It's never aliens.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/27/2017 12:09 PM
A short paper discussing possible origins for `Oumuamua.

It makes a reasonable argument for a young age and has a less extreme aspect ratio of 6:1.

Quote
With a hyperbolic trajectory around the Sun, `Oumuamua is the first confirmed interstellar object. However, its origin is poorly known. By simulating the orbits of 0.23 million local stars, we find 109 encounters with periastron less than 5 pc. `Oumuamua's low peculiar velocity is suggestive of its origin from a young stellar association with similar velocity. In particular, we find that `Oumuamua would have had slow encounters with at least five young stars belonging to the Local Association thus suggesting these as plausible sites for formation and ejection. In addition to an extremely elongated shape, the available observational data for `Oumuamua indicates a red colour suggestive of a potentially organic-rich and activity-free surface. These characteristics seem consistent with formation through energetic collisions between planets and debris objects in the middle part of a young stellar system. We estimate an abundance of about 6.0×10−3 au−3 for such interstellar objects with mean diameter larger than 100 m and find that it is likely that most of them will be ejected into the Galactic halo. Our Bayesian analysis of the available light curves indicates a rotation period of 6.96+1.45−0.39 h which is consistent with the estimation by Meech et al. 2017 and shorter than other literature. The codes and results are available on GitHub.

https://arxiv.org/abs/1711.08800 (https://arxiv.org/abs/1711.08800)

--- Tony
It's not aliens. It's never aliens.

It’s never aliens until it is.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: RotoSequence on 11/27/2017 12:16 PM
It’s never aliens until it is.

One day, but probably not today.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Star One on 11/27/2017 12:18 PM
It’s never aliens until it is.

One day, but probably not today.

Just hope that day is before I kick the bucket.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Johnnyhinbos on 11/27/2017 12:43 PM
It’s never aliens until it is.

One day, but probably not today.

Just hope that day is before I kick the bucket.
(could be one and the same...)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 11/28/2017 01:40 AM
A general method for assessing the origin of interstellar small bodies: the case of 1I/2017 U1 (Oumuamua) (https://arxiv.org/abs/1711.09397)

With the advent of more and deeper sky surveys, the discovery of interstellar small objects entering into the Solar System has been finally possible. In October 19, 2017, using observations of the PANSTARRS survey, a fast moving object, now officially named 1I/2017 U1 (Oumuamua), was discovered in a heliocentric unbound trajectory suggesting an interstellar origin. Assessing the provenance of interstellar small objects is key for understanding their distribution, spatial density and the processes responsible for their ejection from planetary system. However, their peculiar trajectories place a limit on the number of observations available to determine a precise orbit. As a result, when its position is propagated ∼10^5−10^6 years backward in time, small errors in orbital elements become large uncertainties in position in the interstellar space. In this paper we present a general method for assigning probabilities to nearby stars of being the parent system of an observed interstellar object. We describe the method in detail and apply it for assessing the origin of 1I/2017 U1. A preliminary list of potential progenitors and their corresponding probabilities is provided. In the future, when further information about the object and/or the nearby stars be refined, the probabilities computed with our method can be updated.

Implications of the interstellar object 1I/'Oumuamua for planetary dynamics and planetesimal formation (https://arxiv.org/abs/1711.09599)

The first bona-fide interstellar planetesimal -- the ~100 m-sized 1I/'Oumuamua -- was discovered passing through our Solar System on a hyperbolic orbit. This object was likely ejected from a distant star system and provides constraints that on average ~1 Earth mass of planetesimals are ejected per Solar mass of Galactic stars. Using simulations of giant planet dynamics that include rocky and icy planetesimals, we find that this average mass ejection efficiency is consistent with known exoplanet populations if 'Oumuamua was an icy planetesimal in a population dominated (by mass) by similar small bodies. An asteroidal composition is dynamically disfavoured, and would require both high masses for typical asteroid belts and a low ratio by number of icy to rocky planetesimals. Regardless of the composition, it is unlikely that we would have found an object like 'Oumuamua if it samples a broad planetesimal mass function that is dominated by massive objects. Further detections may therefore place strong constraints on predictions for the planetesimal mass function from streaming instability-induced collapse, or point to unexpected collisional or dynamical evolution taking place at large radii in planet-forming discs around young stars.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: sanman on 11/30/2017 01:56 PM
Apparently Musk's BFR might be capable of a mission to catch up with the interstellar object:

https://www.scientificamerican.com/article/spacex-rsquo-s-planned-giant-rocket-could-chase-down-interstellar-asteroid/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 12/01/2017 01:10 AM
1I/'Oumuamua is tumbling (https://arxiv.org/abs/1711.11530)

The discovery of 1I/2017 U1 ('Oumuamua) has provided the first glimpse of a planetesimal born in another planetary system. This interloper exhibits a variable colour, within a range that is broadly consistent with local small bodies such as the P/D type asteroids, Jupiter Trojans, and dynamically excited Kuiper Belt Objects. 1I/'Oumuamua appears unusually elongated in shape, with an axial ratio exceeding 5:1. Rotation period estimates are inconsistent and varied, with reported values between 6.9 and 8.3 hours. Here we analyse all reliable optical photometry reported to date. No single rotation period can explain the exhibited brightness variations. Rather, 1I/'Oumuamua appears to be in an excited rotational state undergoing Non-Principal Axis (NPA) rotation, or tumbling. A satisfactory solution has apparent lightcurve frequencies of 0.135 and 0.126 hr-1 and implies a longest-to-shortest axis ratio of 5:1, though the available data are insufficient to uniquely constrain the true frequencies and shape. Assuming a body that responds to NPA rotation in a similar manner to Solar System asteroids and comets, the timescale to damp 1I/'Oumuamua's tumbling is at least a billion years. 1I/'Oumuamua was likely set tumbling within its parent planetary system, and will remain tumbling well after it has left ours.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Mongo62 on 12/04/2017 01:40 AM
Tumbling motion of 1I/'Oumuamua reveals body's violent past (https://arxiv.org/abs/1712.00437)

Models of the Solar System evolution show that almost all the primitive material leftover from the formation of the planets was ejected to the interstellar space as a result of dynamical instabilities. Accordingly, minor bodies should also be ejected from other planetary systems and should be abundant in the interstellar space. The number density of such objects, and prospects for their detection as they penetrate through the Solar System, were speculated about for decades, recently rising high hopes with the Pan-STARRS and LSST surveys. These expectations materialized on 18 October 2017 with the Pan-STARRS's discovery of 1I/'Oumuamua. Here we report homogeneous photometric observations of this body from Gemini North, which densely cover a total of 8 hr over two nights. A combined ultra-deep image of 1I/'Oumuamua shows no signs of cometary activity, confirming the results from earlier, less sensitive searches. Our data also show an enormous range of brightness variations > 2.5 mag, larger than ever observed in the population of Solar System objects, suggesting a very elongated shape of the body. But most significantly, the light curve does not repeat exactly from one rotation cycle to another and its double-peaked periodicity of 7.5483 ± 0.0073 hr from our data is inconsistent with earlier determinations. These are clear signs of a tumbling motion, a remarkable characteristic of 1I/'Oumuamua's rotation, consistent with a catastrophic collision in the distant past. This first example of an impacted minor body of exosolar origin indicates that collisional evolution of minor body populations in other planetary systems is not uncommon.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: Ludus on 12/04/2017 10:08 PM
https://phys.org/news/2017-11-lyra-mission-interstellar-asteroid.html (https://phys.org/news/2017-11-lyra-mission-interstellar-asteroid.html)

Project Lyra

Paper on Project Lyra (https://www.researchgate.net/publication/320990957_Project_Lyra_Sending_a_Spacecraft_to_1I'Oumuamua_former_A2017_U1_the_Interstellar_Asteroid)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/06/2017 12:54 AM
1I/`Oumuamua as a Tidal Disruption Fragment From a Binary Star System (https://arxiv.org/abs/1712.01823)

1I/`Oumuamua is the first known interstellar small body, probably being only about 100 m in size. Against expectations based on comets, `Oumuamua does not show any activity and has a very elongated figure, and also exhibits undamped rotational tumbling. In contrast, `Oumuamua's trajectory indicates that it was moving with the local stars, as expected from a low-velocity ejection from a relatively nearby system. Here we assume that `Oumuamua is typical of 100-m interstellar objects, and speculate on its origins. We find that giant planets are relatively inefficient at ejecting small bodies from inner solar systems of main-sequence stars, and that binary systems offer a much better opportunity for ejections of non-volatile bodies. We also conclude that `Oumuamua is not a member of a collisional population, which could explain its dramatic difference from small asteroids. We observe that 100 m small bodies are expected to carry little mass in realistic collisional populations, and that occasional events when whole planets are disrupted in catastrophic encounters may dominate interstellar population of 100 m fragments. Unlike the Sun or Jupiter, red dwarf stars are very dense and are capable of thoroughly tidally disrupting terrestrial planets. We conclude that the origin of `Oumuamua as a fragment from a planet that was tidally disrupted and then ejected by a dense member of a binary system could explain its peculiarities.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 12/07/2017 05:08 PM
Is 1I/2017 U1 really of interstellar origin? (https://arxiv.org/abs/1711.05735)

Here we investigate the possibility that the asteroid 1I/2017 U1 actually is a Solar System object, currently expelled from the Solar System by the recent encouter with a Solar System planet. We show that this possibility is extremely unlikeley and that 1I/2017 U1 really is an interstellar object.

This talks about the chances of it passing near the hypothetical Planet 9. Even if it did, how would that explain the 26 km/s of heliocentric boost when the orbital velocities hundreds of AU from the Sun are mere fractions of that.
A research note from Jason Wright does the math to confirm this:
On Distinguishing Interstellar Objects Like 'Oumuamua From Products of Solar System Scattering (http://iopscience.iop.org/article/10.3847/2515-5172/aa9f23/meta)
Quote
1. Could 'Oumuamua Possibly Be a Solar System Object?

The recent discovery of the apparently interstellar3 asteroid 1I/2017 U1 ('Oumuamua)4 has led to speculation about its origin. (Schneider 2017) explored the possibility that it is a solar system object scattered from a solar system planet and concludes that none of the known planets could be the scatterer, nor could the hypothetical "Planet Nine" proposed by Batygin & Brown (2016). Schneider (2017) concludes that if 'Oumuamua is a solar system object, it must have been scattered by "another, yet unknown planet."

If this were true, then one might search for such a planet in the directions of the incoming trajectory of 'Oumuamua and similar objects discovered in the future. However, the orbital energy of 'Oumuamua is too large to be the result of a single scattering event from any hypothetical solar system object
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: llanitedave on 12/10/2017 04:29 PM
A derelict would be so cool...   However that idea suffers from the same probability problem - what are the odds that it would tumble in just in the exact moment in time that humanity gained the instruments to detect such an object?
Another way to look at it: We know that the average star system in the galaxy should have ejected billions of natural objects. We don't know how many artificial objects the average system produces, but it seems safe to assume it's a significantly lower number. Our own system is estimated to have lost ~ Earth masses worth of natural objects, and has only sent a handful of artificial ones.

For chance encounters with randomly drifting stuff, the odds should overwhelmingly favor rocks.
I don't believe the alien hypothesis at all.. but just to have some fun with this:

If this thing were alien technology then yes, that would imply that it wasn't the first, that hundreds of alien objects tumble though our solar system every year and have been doing so for a billion years. Statistically, it would be >50% of every interstellar object. This race would totally dominate the space between stars in our galaxy, so maybe it is 100%

I picture it more like cells in an organism. They give not the slightest damn about us. They may not even care or think about suns. After all, we don't often think about the molten core beneath our feet.

Watch out, because some of the cells are probably antibodies. Fermi paradox resolved.

I had to make sure my vaccinations were up to date after reading this.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Jeff Lerner on 12/10/2017 04:49 PM
Ok...can't resist....since there's been so much speculation on what the object can be...here's my $0.02..

...superior alien race tosses these objects around the galaxy like a stick for a dog to chase and fetch....object passes through a system, no activity, it moves on to the next system..someone goes after it, object signals back to owners that someone is around who they might want to pay attention to...lol
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: kch on 12/10/2017 05:12 PM
It’s never aliens until it is.

One day, but probably not today.

Just hope that day is before I kick the bucket.

(could be one and the same...)

Cookbook?  ;)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 12/11/2017 07:25 PM
Breakthrough Listen is to scan Oumuamua just to make sure it isn’t an alien spaceship.

Here’s the press release.

Quote
San Francisco – December 11, 2017 – Breakthrough Listen, the global astronomical program searching for evidence of civilizations beyond Earth, announced that it is currently focusing its observational efforts on ‘Oumuamua, the mysterious interloper recently spotted moving rapidly through the solar system.
‘Oumuamua was discovered by the Pan-STARRS project at the University of Hawaii in October 2017, passing Earth at about 85 times the distance to the Moon – a stone’s throw, in astronomical terms. It is the first object discovered in the solar system that appears to originate from another star system. Its high speed – 196,000 mph at its peak – suggests it is not gravitationally bound to the Sun, but will continue its voyage back into interstellar space. It has a highly unusual structure for an asteroid – an elongated cigar shape, hundreds of meters in length but with width and height perhaps only one tenth as long.
Researchers working on long-distance space transportation have previously suggested that a cigar or needle shape is the most likely architecture for an interstellar spacecraft, since this would minimize friction and damage from interstellar gas and dust. While a natural origin is more likely, there is currently no consensus on what that origin might have been, and Breakthrough Listen is well positioned to explore the possibility that ‘Oumuamua could be an artifact.
Listen’s observation campaign will begin on Wednesday, December 13 at 3:00 pm ET. Using the Robert C. Byrd Green Bank Telescope, it will continue to observe ‘Oumuamua across four radio bands, from 1 to 12 GHz. Its first phase of observations will last a total of 10 hours, divided into four “epochs” based on the object’s period of rotation.
‘Oumuamua is now about 2 astronomical units (AU) away, or twice the distance between Earth and the Sun. This is closer by a factor of 50-70 than the most distant human artifact, the Voyager I spacecraft. At this distance, it would take under a minute for the Green Bank instrument to detect an omnidirectional transmitter with the power of a cellphone.
“‘Oumuamua’s presence within our solar system affords Breakthrough Listen an opportunity to reach unprecedented sensitivities to possible artificial transmitters and demonstrate our ability to track nearby, fast-moving objects,” said Listen’s Andrew Siemion, Director of Berkeley SETI Research Center. “Whether this object turns out to be artificial or natural, it’s a great target for Listen.”
Even if no signal or other evidence of extraterrestrial technology is heard, Listen observations will cover portions of the radio spectrum in which the object has not yet been observed, and could provide important information about the possibility of water/ice, or the chemistry of a coma (gaseous envelope), neither of which have yet been identified. Listen has already proved its value for traditional, non-SETI astronomy: in August 2017 it detected several dozen repeating fast radio bursts (FRBs) from a distant dwarf galaxy – for details see www.astronomerstelegram.org/?read=10675.

http://breakthroughinitiatives.org/news/14
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 12/11/2017 08:58 PM
Scanning for signs of technology:

https://www.theatlantic.com/science/archive/2017/12/yuri-milner-oumuamua-interstellar-asteroid/547985/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 12/12/2017 08:35 PM
Spitzer data on the ground: https://twitter.com/astrokiwi/status/940560728188125186

Laughlin & Batygin research note seen earlier as a pre-print (http://forum.nasaspaceflight.com/index.php?topic=44075.msg1747041#msg1747041) published: On the Consequences of the Detection of an Interstellar Asteroid (http://iopscience.iop.org/article/10.3847/2515-5172/aaa02b/meta)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/13/2017 01:28 AM
Explaining the elongated shape of 'Oumuamua by the Eikonal abrasion model (https://arxiv.org/abs/1712.04409)

The photometry of the minor body with extrasolar origin (1I/2017 U1) 'Oumuamua revealed an unprecedented shape: Meech et al. (2017) reported a shape elongation b/a close to 1/10, which calls for theoretical explanation. Here we show that the abrasion of a primordial asteroid by a huge number of tiny particles ultimately leads to such elongated shape. The model (called the Eikonal equation) predicting this outcome was already suggested in Domokos et al. (2009) to play an important role in the evolution of asteroid shapes.

Ejection of rocky and icy material from binary star systems: Implications for the origin and composition of 1I/`Oumuamua (https://arxiv.org/abs/1712.04435)

In single star systems like our own Solar system, comets dominate the mass budget of bodies that are ejected into interstellar space, since they form further away and are less tightly bound. However 1I/`Oumuamua, the first interstellar object detected, appears asteroidal in its spectra and in its lack of detectable activity. We argue that the galactic budget of interstellar objects like 1I/`Oumuamua should be dominated by planetesimal material ejected during planet formation in circumbinary systems, rather than in single star systems or widely separated binaries. We further show that in circumbinary systems, rocky bodies should be ejected in comparable numbers to icy ones. This suggests that a substantial fraction of additional interstellar objects discovered in the future should display an active coma. We find that the rocky population, of which 1I/`Oumuamua seems to be a member, should be predominantly sourced from A-type and late B-star binaries.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: JasonAW3 on 12/13/2017 03:04 AM
Scanning for signs of technology:

https://www.theatlantic.com/science/archive/2017/12/yuri-milner-oumuamua-interstellar-asteroid/547985/

Probably wouldn't be a bad idea to point an x-ray telescope at this asteroid.  An IR check could also be useful, primarily to get an idea of stresses from its' tumbling.  Any chance of getting radar images of it, or is it too far out now?
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 12/13/2017 05:02 PM
Decent summation of where we stand now with our knowledge of Oumuamua.

https://www.youtube.com/watch?v=Abr4VcT3Dmw
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: whitelancer64 on 12/13/2017 05:25 PM
Scanning for signs of technology:

https://www.theatlantic.com/science/archive/2017/12/yuri-milner-oumuamua-interstellar-asteroid/547985/

Probably wouldn't be a bad idea to point an x-ray telescope at this asteroid.  An IR check could also be useful, primarily to get an idea of stresses from its' tumbling.  Any chance of getting radar images of it, or is it too far out now?

It has already been observed in IR, by Spitzer. Hubble was also used for observations. It is currently farther from the Sun than Mars is, much too far for good radar data on it. Had we discovered it before its closest approach to Earth (which was still 24 million kilometers, 15 million miles away), we could have gotten some OK radar images of it.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Zed_Noir on 12/14/2017 01:36 AM
Decent summation of where we stand now with our knowledge of Oumuamua.

https://www.youtube.com/watch?v=Abr4VcT3Dmw

Doesn't rule anything out except that it is unlikely to be pile of stuff from accumulated space debris.



Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 12/14/2017 01:51 AM
Space Time did an episode on Oumuamua  :)

https://www.youtube.com/watch?v=nYGs92-qnFY
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Dao Angkan on 12/14/2017 07:15 PM
Sky News in the UK had a live interview yesterday with one of the SETI guys at one of their observatories in the US. The presenter did a good job of asking sensible questions for what could be a sensationalist story, and the SETI guy did a good job of explaining what they're doing to the lay-person. There was even a discussion on the difference between METI and SETI (the presenter brought up that Stephen Hawking says that we should hide from ET), the SETI guy acknowledged that there is a big debate about this, but he falls on the "hide" side, and that SETI only listens.

It was a fun news piece (which is always welcome), whilst also showing science and astronomy in a good light. I don't know if SETI will ever find anything, but I think they do a good job of inspiring people and making space fun.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ncb1397 on 12/14/2017 08:09 PM
Quote
Interstellar Visitor Stays Silent: No Signs of Life Yet on 'Oumuamua
https://www.space.com/39100-interstellar-object-oumuamua-alien-life-search.html?utm_source=notification

Probably not the best strategy to broadcast on the net when you will be listening if you want to pick something up from something that may not want you picking anything up. But any signals would likely be directional and thus this will probably only pick up anything if it was trying to make contact.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Dao Angkan on 12/14/2017 08:54 PM
Quote
Interstellar Visitor Stays Silent: No Signs of Life Yet on 'Oumuamua
https://www.space.com/39100-interstellar-object-oumuamua-alien-life-search.html?utm_source=notification

Probably not the best strategy to broadcast on the net when you will be listening if you want to pick something up from something that may not want you pick anything up. But any signals would likely be directional and thus this will probably only pick up anything if it was trying to make contact.

So we can say that they're not METI at least! :)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: JasonAW3 on 12/14/2017 11:31 PM
Scanning for signs of technology:

https://www.theatlantic.com/science/archive/2017/12/yuri-milner-oumuamua-interstellar-asteroid/547985/

Probably wouldn't be a bad idea to point an x-ray telescope at this asteroid.  An IR check could also be useful, primarily to get an idea of stresses from its' tumbling.  Any chance of getting radar images of it, or is it too far out now?

It has already been observed in IR, by Spitzer. Hubble was also used for observations. It is currently farther from the Sun than Mars is, much too far for good radar data on it. Had we discovered it before its closest approach to Earth (which was still 24 million kilometers, 15 million miles away), we could have gotten some OK radar images of it.

This may seem slightly off topic, but it might not be a bad idea to orbit a few radio telescopes, maybe in the Earth - Moon Lagrange points, or possibly the solar Lagrange points.  A strong RF point source that could be used for long range radio mapping wouldn't be a bad idea as well.  Not only would they be useful for stellar observation, but useful for deep space observation of asteroids, comets, planets and other unusual objects.

      We could probably use inflatable structures for the telescopes, as this would provide the most structure for the least mass.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 12/16/2017 10:35 PM
Karen Meech and collaborators secured additional HST time http://www.stsci.edu/cgi-bin/get-proposal-info?id=15447&observatory=HST

Quote
We request four additional HST/WFC3/UVIS orbits of 1I/217 U1 ('Oumuamua), our Solar System's first interstellar visitor, in order to complete our DD program 15405. Our science goal is to obtain precise astrometry along an extended arc length in order  to identify the region from which this object originated. Since the rotational light curve of 'Oumuamua shows variations of as much as 2.5 mag in brightness, a secure detection in the HST single exposures needed to maximize astrometric precision can only be assured in observations conducted at light curve maximum. However, we and other teams have recently determined that `Oumuamua is in a state of excited rotation and that, contrary to our intial expectations, we cannot predict the rotational phase in early January from existing data. We thus request four additional HST orbits that will allow us to sample `Oumuamua's light curve at multiple rotation phases, thereby ensuring that program 15405 will obtain a secure, final detection of our target that is crucial for this program to achieve its scientific objective.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 12/18/2017 03:52 PM
Interstellar object ‘Oumuamua covered in 'thick crust of carbon-rich gunk

Quote
The mysterious interstellar object ‘Oumuamua that is shooting through our solar system is wrapped in a thick coating of carbon-rich gunk that built up on its cosmic travels, astronomers have found.

New observations of the cigar-shaped body found evidence for a deep surface layer that formed when organic ices – such as frozen carbon dioxide, methane and methanol – that make up the object were battered by the intense radiation that exists between the stars.

https://www.theguardian.com/science/2017/dec/18/interstellar-object-oumuamua-covered-in-thick-crust-of-carbon-rich-gunk
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: jebbo on 12/18/2017 04:26 PM
The paper cited above:

Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 ‘Oumuamua
Quote
During the formation and evolution of the Solar System, significant numbers of cometary and asteroidal bodies were ejected into interstellar space1,2. It is reasonable to expect that the same happened for planetary systems other than our own. Detection of such interstellar objects would allow us to probe the planetesimal formation processes around other stars, possibly together with the effects of long-term exposure to the interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known interstellar object, discovered by the Pan-STARRS1 telescope in October 2017 (ref. 3). The discovery epoch photometry implies a highly elongated body with radii of ~ 200 × 20 m when a comet-like geometric albedo of 0.04 is assumed. The observable interstellar object population is expected to be dominated by comet-like bodies in agreement with our spectra, yet the reported inactivity of 'Oumuamua implies a lack of surface ice. Here, we report spectroscopic characterization of ‘Oumuamua, finding it to be variable with time but similar to organically rich surfaces found in the outer Solar System. We show that this is consistent with predictions of an insulating mantle produced by long-term cosmic ray exposure4. An internal icy composition cannot therefore be ruled out by the lack of activity, even though ‘Oumuamua passed within 0.25 au of the Sun.
https://www.nature.com/articles/s41550-017-0361-4?utm_content=bufferc0423&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer (https://www.nature.com/articles/s41550-017-0361-4?utm_content=bufferc0423&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer)
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 12/18/2017 04:52 PM
An ideal habitat for basic life especially as that coating would probably protect it from the worst of interstellar radiation.

Quote
Fitzsimmons' team estimates that outer layer might have reached temperatures as high as 300 degrees Celsius during 'Oumuamua's closest pass of the sun, but that it would have provided enough insulation to prevent ice inside from vaporizing. Which raises the question: Could it have protected life inside the asteroid, perhaps waterborne microbes, from vaporizing as well?

I mean, technically? Yes. But Meech says that a far greater risk to microbial life would be the same cosmic rays that cooked 'Oumuamua's outside in the first place. Only if something were buried deep inside of the asteroid (say, at a distance of a few meters) would it be shielded from the harsh radiation of space.

https://www.wired.com/story/oumuamua-probably-isnt-a-spaceshipbut-it-could-have-passengers/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/19/2017 01:01 AM
On Distinguishing Interstellar Objects Like `Oumuamua From Products of Solar System Scattering (https://arxiv.org/abs/1712.06044)

Schneider (2018) explored the possibility that 'Oumuamua is a Solar System object, and concluded that if it is, it must have been scattered by "another, yet unknown planet." I provide an extremely conservative upper limit on post-scattering velocities in the Solar System to show that 'Oumuamua is moving far to quickly to be the result of any hypothetical single scattering event between any bound Solar System objects within 21 au (a distance within which our understanding of objects capable of scattering 'Oumuamua is presumably complete).
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 12/19/2017 05:44 AM
Fitzsimmons paper sans paywall on arxiv Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 'Oumuamua (https://arxiv.org/abs/1712.06552)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/20/2017 12:55 AM
What and Whence 1I/`Oumuamua? (https://arxiv.org/abs/1712.06721)

The first confirmed interstellar interloper in our Solar System, 1I/`Oumuamua, is likely to be a minor body ejected from another star, but its brief flyby and faintness made it difficult to study. Two remarkable properties are its large (2-2.5 mag) rotational variability and its motion relative to the Sun before encounter. The former suggests an extremely elongated (>10:1) shape and the latter an origin from the protoplanetary disk of a young star in a nearby association. 1I/`Oumuamua's variability can also be explained if it is a contact binary of near-equilibrium ellipsoidal components and heterogeneous surfaces, i.e. brighter, dust-mantled inner-facing hemispheres and darker, dust-free outer-facing poles. The probability that 1I/`Oumuamua has the same motion as a young stellar association is <1%. One explanation for the youth of 1I/`Oumuamua relative to the Solar neighborhood mean it that loss of dust mantles and darkening of lag surfaces by cosmic rays renders similar objects undetectable in a few 100's of Myr. In this scenario, 1I/`Oumuamua is smaller and much less massive, but represents a more numerous population of ejected planetesimals. Studies of such objects are a potential means to probe early planet formation, complementing observations of protoplanetary disks and studies of meteorites.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/21/2017 02:34 AM
Ejection of material --"Jurads" -- from post main sequence planetary systems (https://arxiv.org/abs/1712.07247)

We show that the rate of pollution of white dwarfs by asteroidal material implies a concomitant rate of material ejection that can contribute significantly to the population of interstellar minor bodies. We note also that the irradiation during post main sequence evolution implies that much of this ejected material may lose volatiles, providing a rationale for the curious properties of the recently discovered interstellar object Oumuamua.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Ben the Space Brit on 12/21/2017 08:56 AM
Did I read that right? Basically, this suggestion is that Oumanuamua is basically a tiny solid bit of a planetary nebulae that has zipped by, aeons after being blown out of its home system by the dissolution of its primary?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper?
Post by: vapour_nudge on 12/21/2017 09:33 AM
I think that there has been a lot of unsupported speculation on this thread. What do we know for a fact about this object?

1. Definitely interstellar in origin, moving at close to the general velocity of gravitationally unbound objects in this part of the Galaxy.

2. There has been no obvious originating exoplanetary system found so far. There are a few possibilities, but all of them appear to have a low probability of being the originating system.

3. The reddish color slope of the object is consistent with an outer solar system object, either asteroidal or cometary. Its color is consistent with a variety of compositions, and in fact is exactly what would be expected for a dormant comet nucleus.

4. The shape derived from its light curve is highly unusual (but not unheard of) for a rocky asteroidal object, but comet nuclei have been found to frequently be quite elongated, although not as elongated as this object appears to be. A small sample size warning for comet nuclei, though.

5. Part of the light curve variations might be due to compositional differences, bringing its shape into the normal range.

6. Its rotation period of around 8 hours is not unusual, and is well over the limit for "rubble piles" of its size.

Conclusion: what we know of this object is consistent with a natural origin in the outer portions of an unidentified exoplanetary system.

Great post which is back to facts. I suspect the feelings of some are: "we can't prove it is not an alien created/manipulated object so it just might be".

It's hard to argue the point with those who just "want" to believe that stuff. We can't prove it isn't a giant dog - or a 1000x scale Tesla Roadster for that matter - but seeing the concise facts posted is great

I read an article recently and can't find it but it suggests the size is possibly a bit over 6:1 ratio now. Initial data suggested 10:1. It's great to see how the data is being refined. We live in exciting times; we don't need alien talk to make it exciting
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 12/21/2017 11:07 AM
I think that there has been a lot of unsupported speculation on this thread. What do we know for a fact about this object?

1. Definitely interstellar in origin, moving at close to the general velocity of gravitationally unbound objects in this part of the Galaxy.

2. There has been no obvious originating exoplanetary system found so far. There are a few possibilities, but all of them appear to have a low probability of being the originating system.

3. The reddish color slope of the object is consistent with an outer solar system object, either asteroidal or cometary. Its color is consistent with a variety of compositions, and in fact is exactly what would be expected for a dormant comet nucleus.

4. The shape derived from its light curve is highly unusual (but not unheard of) for a rocky asteroidal object, but comet nuclei have been found to frequently be quite elongated, although not as elongated as this object appears to be. A small sample size warning for comet nuclei, though.

5. Part of the light curve variations might be due to compositional differences, bringing its shape into the normal range.

6. Its rotation period of around 8 hours is not unusual, and is well over the limit for "rubble piles" of its size.

Conclusion: what we know of this object is consistent with a natural origin in the outer portions of an unidentified exoplanetary system.

Great post which is back to facts. I suspect the feelings of some are: "we can't prove it is not an alien created/manipulated object so it just might be".

It's hard to argue the point with those who just "want" to believe that stuff. We can't prove it isn't a giant dog - or a 1000x scale Tesla Roadster for that matter - but seeing the concise facts posted is great

I read an article recently and can't find it but it suggests the size is possibly a bit over 6:1 ratio now. Initial data suggested 10:1. It's great to see how the data is being refined. We live in exciting times; we don't need alien talk to make it exciting

Talk about making unrealistic comparisons to try and prove an argument. All that does it make your argument look weak and you’re not going to convince anyone that way.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/21/2017 02:41 PM
Did I read that right? Basically, this suggestion is that Oumanuamua is basically a tiny solid bit of a planetary nebulae that has zipped by, aeons after being blown out of its home system by the dissolution of its primary?

The paper basically states that just as considerable asteroidal / cometary material is being regularly accreted by white dwarfs, other asteroidal / cometary material must be ejected, possibly comprising a significant fraction of all small interstellar objects.

Such material would have been baked by the preceding red giant phase for several million years, resulting in the sort of composition we see with 'Oumuamua.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 12/22/2017 01:05 AM
Prospects for Backtracing 1I/`Oumuamua and Future Interstellar Objects (https://arxiv.org/abs/1712.08059)

1I/`Oumuamua is the first of likely many small bodies of extrasolar origin to be found in the solar system. These interstellar objects (ISOs) are hypothesized to have formed in extrasolar planetary systems prior to being ejected into interstellar space and subsequently arriving at the solar system. This paper discusses necessary considerations for tracing ISOs back to their parent stars via trajectory analysis, and places approximate limits on doing so. Results indicate the capability to backtrace ISOs beyond the immediate solar neighborhood is presently constrained by the quality of stellar astrometry, a factor poised for significant improvement with upcoming Gaia data releases. Nonetheless, prospects for linking 1I or any other ISO to their respective parent star appear unfavorable on an individual basis due to gravitational scattering from random stellar encounters which limit traceability to the past few tens of millions of years. These results, however, do not preclude the possibility of occasional success, particularly after considering the potential for observational bias favoring the discovery of younger ISOs, together with the anticipated rise in the ISO discovery rate under forthcoming surveys.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 01/10/2018 12:50 AM
1I/2017 'Oumuamua-like Interstellar Asteroids as Possible Messengers from the Dead Stars (https://arxiv.org/abs/1801.02658)

Discovery of the first interstellar asteroid (ISA) - 1I/2017 'Oumuamua - raised a number of questions regarding its origin. Many of them relate to its lack of cometary activity, suggesting refractory composition of 'Oumuamua. Here we explore the possibility that 'Oumuamua-like ISAs are produced in tidal disruption events (TDEs) of refractory planetoids (asteroids, dwarf planets, etc.) by the white dwarfs (WDs). This idea is supported by existing spectroscopic observations of metal-polluted WDs, hinting at predominantly volatile-poor composition of accreted material. We show that such TDEs sourced by realistic planetary systems (including a population of >1000 km planetoids and massive perturbers - Neptune-to-Saturn mass planets) can eject to interstellar space up to 30% of planetary mass involved in them. Collisional fragmentation, caused by convergent vertical motion of the disrupted planetoid's debris inside the Roche sphere of the WD, channels most of the original mass into 0.1-1 km fragments, similar to 'Oumuamua. Such size spectrum of ISAs (very different from the top-heavy distributions expected in other scenarios) implies that every WD needs to eject ~0.3M_E of refractory material through TDEs (for ISA albedo of 0.2). This figure is consistent with the existing observations of WD metal pollution once we account for observational biases by using realistic models of circum-WD planetary systems. ISAs should exhibit kinematic characteristics similar to old, dynamically hot Galactic populations; we interpret 'Oumuamua's slow Galactic motion as a statistical fluctuation. ISA ejection in individual planetary TDEs is highly anisotropic, resulting in large fluctuations of their space density. We also show that other ISA production mechanisms involving stellar remnants - direct ejection by massive planets around WDs and SN explosions - have difficulty explaining 'Oumuamua-like ISAs.

Interstellar Interlopers: Number Density and Origins of 'Oumuamua-like Objects (https://arxiv.org/abs/1801.02821)

We provide a calculation of Pan-STARRS' ability to detect objects similar to the interstellar object 1I/2017 U1 (hereafter 'Oumuamua), including the most detectable approach vectors and the effect of object size on detection efficiency. Using our updated detection cross-section, we infer an interstellar number density of such objects (nIS≈0.2 au−3). This translates to a mass density of ρIS≈4M⊕ pc−3 which cannot be populated unless every star is contributing. We find that given current models, such a number density cannot arise from the ejection of inner solar system material during planet formation. We note that a stellar system's Oort cloud will be released after a star's main sequence life time and may provide enough material to obtain the observed density. The challenge is that Oort cloud bodies are icy and \OBJECT was observed to be dry which necessitates a crust generation mechanism.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 01/10/2018 02:08 AM
Breakthrough Listen Observations of Breakthrough Listen with the GBT (https://arxiv.org/abs/1801.02814) (typo in original , they meant 'Oumuamua :o)

Quote
We have conducted a search for radio emission consistent with an artificial source targeting 1I/'Oumuamua with the Robert C. Byrd Green Bank Telescope (GBT) between 1.1 and 11.6 GHz. We searched the data for narrow band signals and found none. Given the close proximity to this interstellar object, we can place limits to putative transmitters with extremely low power (0.08 W).
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 01/19/2018 08:38 PM
Update on an Interstellar Asteroid

Quote
What’s the news coming from the research world on the interstellar asteroid visitor, asteroid 1I/’Oumuamua? Read on for an update from a few of the latest studies.

http://aasnova.org/2018/01/19/update-on-an-interstellar-asteroid/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 01/25/2018 05:22 PM
‘Oumuamua talks by Meg Schwamb and Matija Cuk at the SETI institute, Jan 23

https://www.youtube.com/watch?v=b_vAcv7JGhQ

Nothing really new for those who have followed the preprints, but a good overview.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: speedevil on 01/28/2018 05:52 AM
Has there been any work done on estimating if any of the prior surveys for asteroids/... may have caught these optically, and not picked them up due to searching only for bound bodies to improve performance?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 02/05/2018 12:38 AM
Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies (https://arxiv.org/abs/1802.00778)

Observed hyperbolic minor bodies might have an interstellar origin, but they can be natives of the Solar system as well. Fly-bys with the known planets or the Sun may result in the hyperbolic ejection of an originally bound minor body; in addition, members of the Oort cloud could be forced to follow inbound hyperbolic paths as a result of secular perturbations induced by the Galactic disc or, less frequently, due to impulsive interactions with passing stars. These four processes must leave distinctive signatures in the distribution of radiants of observed hyperbolic objects, both in terms of coordinates and velocity. Here, we perform a systematic numerical exploration of the past orbital evolution of known hyperbolic minor bodies using a full N-body approach and statistical analyses to study their radiants. Our results confirm the theoretical expectations that strong anisotropies are present in the data. We also identify a statistically significant overdensity of high-speed radiants towards the constellation of Gemini that could be due to the closest and most recent known fly-by of a star to the Solar system, that of the so-called Scholz's star. In addition to and besides 1I/2017 U1 (`Oumuamua), we single out eight candidate interstellar comets based on their radiants' velocities.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 02/06/2018 12:45 AM
Spinup and Disruption of Interstellar Asteroids by Mechanical Torques, and Implications for 1I/2017 U1 (`Oumuamua) (https://arxiv.org/abs/1802.01335)

The detection of the first interstellar asteroid, 1I/2017 U1 (`Oumuamua), has opened a new era for research on interstellar objects. In this paper, we study the rotational dynamics of interstellar asteroids (ISAs) of irregular shapes moving through the interstellar gas. We find that regular mechanical torques resulting from the bombardment of gas flow on the irregular body could be important for the dynamics and destruction of ISAs. Mechanical torques can spin up the ISA, resulting in the breakup of the original ISA into small binary asteroids when the rotation rate exceeds the critical limit determined by material strength. We find that the breakup timescale is short for ISAs of highly irregular shapes and low tensile strength. We apply our results to the first observed ISA, `Oumuamua, and suggest that its extreme elongated shape may originate from a re-assembly of the binary fragments due to gravity along its journey in the interstellar medium. The tumbling of `Oumuamua could have been induced by rotational disruption due to mechanical torques. Finally, we discuss the survival possibility of high-velocity asteroids presumably formed by tidal disruption of planetary systems by the black hole at the Galactic center.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 02/08/2018 01:26 AM
Why is Interstellar Object 1I/2017 U1 (`Oumuamua) Rocky, Tumbling and Very Prolate? (https://arxiv.org/abs/1802.02273)

The recently discovered first interstellar object 1I/2017 U1 (`Oumuamua) has brightness that varies by a factor of 10, a range greater than that of any Solar System asteroid, a spectrum characteristic of Type D asteroids, and no evidence of evaporating volatiles, contrary to expectation for exo-Oort clouds. This object was the first example of the proposed "Jurads", objects depleted in volatiles and ejected from planetary systems during the post-main sequence evolution of their parent star. I suggest that heating by the star's giant stage fluidized a precursor cometary object as volatiles escaped, causing it to assume the Jacobi ellipsoidal shape of a self-gravitating incompressible liquid. The collision that produced the inferred tumbling motion must have occurred thousands of years after the formation of 1I/2017 U1 `Oumuamua. Jacobi ellipsoids have a unique relation among rotation rate, density and axial ratio. The inferred axial ratio ⪆5 implies a lower bound on the density of 1.6 g/cm3, excluding an icy interior unless it is almost entirely frozen CO2. This object is the first Jurad to be discovered and may be related to accreting objects that pollute white dwarf atmospheres and may make Soft Gamma Repeaters.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 02/11/2018 08:28 AM
For UK forum members tonight’s Sky At Night is all about Oumuamua.

Feature article.

http://www.bbc.co.uk/news/science-environment-43018706

Episode link.

http://www.bbc.co.uk/programmes/b09rvpts
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: plutogno on 02/11/2018 07:33 PM
The tumbling rotational state of 1I/‘Oumuamua

https://www.nature.com/articles/s41550-018-0398-z
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 02/14/2018 07:31 PM
‘Oumuamua: New Work on Interstellar Objects

https://www.centauri-dreams.org/2018/02/14/oumuamua-new-work-on-interstellar-objects/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 02/27/2018 01:02 AM
A Serendipitous MWA Search for Narrow-band and Broad-band Low Frequency Radio Transmissions from 1I/2017 U1 'Oumuamua (https://arxiv.org/abs/1802.09276)

We examine data from the Murchison Widefield Array (MWA) in the frequency range 72 -- 102 MHz for a field-of-view that serendipitously contained the interstellar object 'Oumuamua on 2017 November 28. Observations took place with time resolution of 0.5 s and frequency resolution of 10 kHz. %This observation was undertaken for another purpose but due to the MWA's extremely large field-of-view, 'Oumuamua was serendipitously observed simultaneously. Based on the interesting but highly unlikely suggestion that 'Oumuamua is an interstellar spacecraft, due to some unusual orbital and morphological characteristics, we examine our data for signals that might indicate the presence of intelligent life associated with 'Oumuamua. We searched our radio data for: 1) impulsive narrow-band signals; 2) persistent narrow-band signals; and 3) impulsive broadband signals. We found no such signals with non-terrestrial origins and make estimates of the upper limits on Equivalent Isotropic Radiated Power (EIRP) for these three cases of approximately 7 kW, 840 W, and 100 kW, respectively. These transmitter powers are well within the capabilities of human technologies, and are therefore plausible for alien civilizations. While the chances of positive detection in any given Search for Extraterrestrial Intelligence (SETI) experiment are vanishingly small, the characteristics of new generation telescopes such as the MWA (and in the future, the Square Kilometre Array) make certain classes of SETI experiment easy, or even a trivial by-product of astrophysical observations. This means that the future costs of SETI experiments are very low, allowing large target lists to partially balance the low probability of a positive detection.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 03/09/2018 01:03 AM
Interstellar object 'Oumuamua as an extinct fragment of an ejected cometary planetesimal (https://arxiv.org/abs/1803.02840)

'Oumuamua was discovered passing through our Solar System on a hyperbolic orbit. It presents an apparent contradiction, with colors similar to those of volatile-rich Solar System bodies but with no visible outgassing or activity during its close approach to the Sun. Here we show that this contradiction can be explained by the dynamics of planetesimal ejection by giant planets. We propose that 'Oumuamua is an extinct fragment of a comet-like planetesimal born in a planet-forming disk that also formed Neptune- to Jupiter-mass giant planets. On its pathway to ejection 'Oumuamua's parent body underwent a close encounter with a giant planet and was tidally disrupted into small pieces, similar to comet Shoemaker-Levy 9's disruption after passing close to Jupiter. We use dynamical simulations to show that 0.1-1% of cometary planetesimals undergo disruptive encounters prior to ejection. Rocky asteroidal planetesimals are unlikely to disrupt due to their higher densities. After disruption, the bulk of fragments undergo enough close passages to their host stars to lose their surface volatiles and become extinct. Planetesimal fragments such as 'Oumuamua contain little of the mass in the population of interstellar objects but dominate by number. Our model makes predictions that will be tested in the coming decade by LSST.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 03/19/2018 08:22 PM
NEWS & PRESS

‘Oumuamua likely came from a binary star system

Last Updated on Monday, 19 March 2018 11:52
Published on Monday, 19 March 2018 11:52
New research finds that 'Oumuamua, the rocky object identified as the first confirmed interstellar asteroid, very likely came from a binary star system.
 
"It's remarkable that we've now seen for the first time a physical object from outside our Solar System," says lead author Dr Alan Jackson, a postdoc at the Centre for Planetary Sciences at the University of Toronto Scarborough in Ontario, Canada.
 
A binary star system, unlike our Sun, is one with two stars orbiting a common centre.
 
For the new study, published in the journal Monthly Notices of the Royal Astronomical Society, Jackson and his co-authors set about testing how efficient binary star systems are at ejecting objects. They also looked at how common these star systems are in the Galaxy.
 
They found that rocky objects like 'Oumuamua are far more likely to come from binary than single star systems. They were also able to determine that rocky objects are ejected from binary systems in comparable numbers to icy objects.
 
"It's really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot and the Solar System ejects many more comets than asteroids," says Jackson, who specializes in planet and solar system formation.
 
Once they determined that binary systems are very efficient at ejecting rocky objects, and that a sufficient number of them exist, they were satisfied that 'Oumuamua very likely came from a binary system. They also concluded that it probably came from a system with a relatively hot, high mass star since such a system would have a greater number of rocky objects closer in.
 
The team suggest that the asteroid was very likely to have been ejected from its binary system sometime during the formation of planets.
 
'Oumuamua, which is Hawaiian for 'scout', was first spotted by the Haleakala Observatory in Hawaii on 19 October 2017. With a radius of 200 metres and travelling at a blistering speed of 30 kilometres per second, at its closest it was about 33,000,000 km from Earth.
 
When it was first discovered researchers initially assumed the object was a comet, one of countless icy objects that release gas when they warm up on approaching the Sun. But it didn't show any comet-like activity as it neared the Sun, and was quickly reclassified as an asteroid, meaning it was rocky.
 
Researchers were also fairly sure it was from outside our Solar System, based on its trajectory and speed. An eccentricity of 1.2 – which classifies its path as an open-ended hyperbolic orbit – and such a high speed meant it was not bound by the gravity of the Sun.
 
In fact, as Jackson points out, 'Oumuamua's orbit has the highest eccentricity ever observed in an object passing through our Solar System.
 
Major questions about ‘Oumuamua remain. For planetary scientists like Jackson, being able to observe objects like these may yield important clues about how planet formation works in other star systems.
 
“The same way we use comets to better understand planet formation in our own Solar System, maybe this curious object can tell us more about how planets form in other systems.”
 
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 03/20/2018 01:06 AM
The Feasibility and Benefits of In Situ Exploration of `Oumuamua-like objects (https://arxiv.org/abs/1803.07022)

A rapid accumulation of observations and interpretation have followed in the wake of 1I `Oumuamua's passage through the inner Solar System. We briefly outline the consequences that this first detection of an interstellar asteroid implies for the planet-forming process, and we assess the near-term prospects for detecting and observing (both remotely and in situ) future Solar System visitors of this type. Drawing on detailed heat-transfer calculations that take both `Oumuamua's unusual shape and its chaotic tumbling into account, we affirm that the lack of a detectable coma in deep images of the object very likely arises from the presence of a radiation-modified coating of high molecular weight material (rather than a refractory bulk composition). Assuming that `Oumuamua is a typical representative of a larger population with a kinematic distribution similar to Population I stars in the local galactic neighborhood, we calculate expected arrival rates, impact parameters and velocities of similar objects and assess their prospects for detection using operational and forthcoming facilities. Using `Oumuamua as a proof-of-concept, we assess the prospects for missions that intercept interstellar objects (ISOs) using conventional chemical propulsion. Using a "launch on detection" paradigm, we estimate wait times of order 10 years between favorable mission opportunities with the detection capabilities of the Large-Scale Synoptic Survey Telescope (LSST), a figure that will be refined as the population of interstellar asteroids becomes observationally better constrained.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 03/28/2018 01:53 AM
Constraints on the Density and Internal Strength of 1I/'Oumuamua (https://arxiv.org/abs/1803.09864)

1I/'Oumuamua was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS 1) on 19 October 2017. Unlike all previously discovered minor planets this object was determined to have eccentricity e>1.0, suggesting an interstellar origin. Since this discovery and within the limited window of opportunity, several photometric and spectroscopic studies of the object have been made. Using the measured light curve amplitudes and rotation periods we find that, under the assumption of a triaxial ellipsoid, a density range 1500<ρ<2800 kg m−3 matches the observations and no significant cohesive strength is required. We also determine that an aspect ratio of 6±1:1 is most likely after accounting for phase-angle effects and considering the potential effect of surface properties. This elongation is still remarkable but less than some other estimates.

Search for OH 18-cm radio emission from 1I/2017 U1 with the Green Bank telescope (https://arxiv.org/abs/1803.10187)

This paper reports the first OH 18-cm line observation of the first detected interstellar object 1I/2017 U1 (`Oumuamua) using the Green Bank Telescope. We have observed the OH lines at 1665.402 MHz, 1667.359, and 1720.53 MHz frequencies with a spectral resolution of 357 Hz (approximately 0.06 km-s^{-1}). At the time of the observation, `Oumuamua was at topocentric distance and velocity of 1.07 au and 63.4 km-s^{-1}, respectively, or at heliocentric distance and velocity of 1.8 au and 39 km-s^{-1}, respectively. Based on a detailed data reduction and an analogy-based inversion, our final results confirm the asteroidal origin of `Oumuamua (as discussed in Meech et al., 2017) with an upper bound of OH production of Q[OH] < 0.17 x 10^{28} s^{-1}.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 04/11/2018 01:26 AM
The Excited Spin State of 1I/2017 U1 `Oumuamua (https://arxiv.org/abs/1804.03471)

We show that `Oumuamua's excited spin could be in a high energy LAM state, which implies that its shape could be far from the highly elongated shape found in previous studies. CLEAN and ANOVA algorithms are used to analyze `Oumuamua's lightcurve using 818 observations over 29.3~days. Two fundamental periodicities are found at frequencies (2.77±0.11) and (6.42±0.18)~cycles/day, corresponding to (8.67±0.34)~h and (3.74±0.11)~h, respectively. The phased data show that the lightcurve does not repeat in a simple manner, but approximately shows a double minimum at 2.77~cycles/day and a single minimum at 6.42~cycles/day. This is characteristic of an excited spin state. `Oumuamua could be spinning in either the long (LAM) or short (SAM) axis mode. For both, the long axis precesses around the total angular momentum vector with an average period of (8.67±0.34)~h. For the three LAMs we have found, the possible rotation periods around the long axis are 6.58, 13.15, or 54.48~h, with 54.48~h being the most likely. `Oumuamua may also be nutating with respective periods of half of these values. We have also found two possible SAM states where `Oumuamua oscillates around the long axis with possible periods at 13.15 and 54.48~h, the latter as the most likely. In this case any nutation will occur with the same periods. Determination of the spin state, the amplitude of the nutation, the direction of the TAMV, and the average total spin period may be possible with a direct model fit to the lightcurve. We find that `Oumuamua is "cigar-shaped"', if close to its lowest rotational energy, and an extremely oblate spheroid if close to its highest energy state for its total angular momentum.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: plutogno on 06/27/2018 06:29 PM
Interstellar asteroid is really a comet
http://sci.esa.int/solar-system/60464-interstellar-asteroid-is-really-a-comet/

and related (paywalled) Nature paper
Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua)
https://www.nature.com/articles/s41586-018-0254-4
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Alpha_Centauri on 06/27/2018 06:56 PM
^^ non-paywall version;

http://www.eso.org/public/archives/releases/sciencepapers/eso1820/eso1820a.pdf
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 06/29/2018 12:31 AM
Ouamuamua's acceleration of 4.92+/-.16 x 10^-6 m/s² is consistent with cometary emissions, and the lack of observed water is consistent with the observed acceleration, but the lack of dust to be seen is not consistent with cometary emissions. Strange.  ???

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Orbiter on 06/29/2018 12:46 AM
Could also be an ion thruster ignition ;)

(I'm kidding, of course)
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 07/01/2018 06:51 PM
Ouamuamua's acceleration of 4.92+/-.16 x 10^-6 m/s² is consistent with cometary emissions, and the lack of observed water is consistent with the observed acceleration, but the lack of dust to be seen is not consistent with cometary emissions. Strange. 

I keep having to explain to people online this is due to it being a comet apparently and it becoming active, not because some alien has put his foot on the accelerator. I blame Arthur C Clarke.

But if it turns around starts heading back towards Earth I am stocking up on supplies. Especially if it starts making whale song.
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 07/01/2018 07:18 PM
Not seen this posted on here and it gives a plausible explanation for the lack of dust detection.

Our Solar System’s First Known Interstellar Object Gets Unexpected Speed Boost

Using observations from NASA’s Hubble Space Telescope and ground-based observatories, an international team of scientists have confirmed ′Oumuamua (oh-MOO-ah-MOO-ah), the first known interstellar object to travel through our solar system, got an unexpected boost in speed and shift in trajectory as it passed through the inner solar system last year.

“Our high-precision measurements of ′Oumuamua’s position revealed that there was something affecting its motion other than the gravitational forces of the Sun and planets," said Marco Micheli of ESA’s (European Space Agency) Space Situational Awareness Near-Earth Object Coordination Centre in Frascati, Italy, and lead author of a paper describing the team's findings.

Analyzing the trajectory of the interstellar visitor, co-author Davide Farnocchia of the Center for Near Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory (JPL) found that the speed boost was consistent with the behavior of a comet.

“This additional subtle force on ′Oumuamua likely is caused by jets of gaseous material expelled from its surface,” said Farnocchia. “This same kind of outgassing affects the motion of many comets in our solar system.”

Comets normally eject large amounts of dust and gas when warmed by the Sun. But according to team scientist Olivier Hainaut of the European Southern Observatory, “there were no visible signs of outgassing from ′Oumuamua, so these forces were not expected.”

The team estimates that ′Oumuamua’s outgassing may have produced a very small amount of dust particles – enough to give the object a little kick in speed, but not enough to be detected.

Karen Meech, an astronomer at the University of Hawaii’s Institute of Astronomy and co-author of the study, speculated that small dust grains, present on the surface of most comets, eroded away during ′Oumuamua's long journey through interstellar space.

"The more we study ′Oumuamua, the more exciting it gets," Meech said. "I'm amazed at how much we have learned from a short, intense observing campaign. I can hardly wait for the next interstellar object!"

′Oumuamua, less than half a mile in length, now is farther away from our Sun than Jupiter and traveling away from the Sun at about 70,000 mph as it heads toward the outskirts of the solar system. In only another four years, it will pass Neptune’s orbit on its way back into interstellar space.

Because ′Oumuamua is the first interstellar object ever observed in our solar system, researchers caution that it’s difficult to draw general conclusions about this newly-discovered class of celestial bodies. However, observations point to the possibility that other star systems regularly eject small comet-like objects and there should be more of them drifting among the stars. Future ground- and space-based surveys could detect more of these interstellar vagabonds, providing a larger sample for scientists to analyze.

https://www.nasa.gov/press-release/our-solar-system-s-first-known-interstellar-object-gets-unexpected-speed-boost
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 07/19/2018 08:22 PM
The story Oumuamua, the first visitor from another star system TED talk by Karen J. Meech

https://www.youtube.com/watch?v=rfi3w9Bzwik
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 08/13/2018 01:23 AM
New papers on this object are becoming uncommon, but are still occasionally appearing.

A kinematical age for the interstellar object 1I/'Oumuamua (https://arxiv.org/abs/1808.03637)

1I/'Oumuamua is the first interstellar object observed passing through the Solar System. Understanding the nature of these objects will provide crucial information about the formation and evolution of planetary systems, and the chemodynamical evolution of the Galaxy as a whole. We obtained the galactic orbital parameters of this object, considering 8 different models for the Galaxy, and compared it to those of stars of different ages from the Geneva-Copenhagen Survey (GCS). Assuming that the galactic orbital evolution of this object is similar to that of stars, we applied a Bayesian analyses and used the distribution of stellar velocities, as a function of age, to obtain a probability density function for the age of 'Oumuamua. We considered two models for the age-velocity dispersion relation (AVR): the traditional power law, fitted using data from the GCS; and a model that implements a second power law for younger ages, which we fitted using a sample of 153 Open Clusters (OCs). We find that the slope of the AVR is smaller for OCs than it is for field stars. Using these AVRs, we constrained an age range of 0.01-1.87 Gyr for 'Oumuamua and characterized a most likely age ranging between 0.20-0.45 Gyr, depending on the model used for the AVR. We also estimated the intrinsic uncertainties of the method due to not knowing the exact value of the Solar motion and the particularities of 1I/'Oumuamua's ejection.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 08/29/2018 01:34 AM
Radio SETI Observations of the Interstellar Object 'Oumuamua (https://arxiv.org/abs/1808.09355)

Motivated by the hypothesis that 'Oumuamua could conceivably be an interstellar probe, we used the Allen Telescope Array to search for radio transmissions that would indicate a non-natural origin for this object. Observations were made at radio frequencies between 1-10 GHz using the Array's correlator receiver with a channel bandwidth of 100 kHz. In frequency regions not corrupted by man-made interference, we find no signal flux with frequency-dependent lower limits of 0.01 Jy at 1 GHz and 0.1 Jy at 7 GHz. For a putative isotropic transmitter on the object, these limits correspond to transmitter powers of 30 mW and 300 mW, respectively. In frequency ranges that are heavily utilized for satellite communications, our sensitivity to weak signals is badly impinged, but we can still place an upper limit of 10 W for a transmitter on the asteroid. For comparison and validation should a transmitter be discovered, contemporaneous measurements were made on the solar system asteroids uz2017 and wc2017 with comparable sensitivities. Because they are closer to Earth, we place upper limits on transmitter power to be 0.1 and 0.001 times the limits for 'Oumuamua. A concurrent set of observations over the same frequency range were made with a narrow-band (1 Hz) beamformer/spectrometer. Setting a 6.5 sigma threshold, the (frequency dependent) sensitivity limits on 'Oumuamua were in the range 175 +/- 25 Jy into a 1 Hz bin. This rules out 1 Hz transmitters on 'Oumuamua, 2017uz, and 2017wc to less than 500 mW, 50 mW, and 0.5 mW respectively over the frequency range from 1-10 GHz.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Zed_Noir on 08/29/2018 09:14 PM
Radio SETI Observations of the Interstellar Object 'Oumuamua (https://arxiv.org/abs/1808.09355)

Motivated by the hypothesis that 'Oumuamua could conceivably be an interstellar probe, we used the Allen Telescope Array to search for radio transmissions that would indicate a non-natural origin for this object. Observations were made at radio frequencies between 1-10 GHz using the Array's correlator receiver with a channel bandwidth of 100 kHz. In frequency regions not corrupted by man-made interference, we find no signal flux with frequency-dependent lower limits of 0.01 Jy at 1 GHz and 0.1 Jy at 7 GHz. For a putative isotropic transmitter on the object, these limits correspond to transmitter powers of 30 mW and 300 mW, respectively. In frequency ranges that are heavily utilized for satellite communications, our sensitivity to weak signals is badly impinged, but we can still place an upper limit of 10 W for a transmitter on the asteroid. For comparison and validation should a transmitter be discovered, contemporaneous measurements were made on the solar system asteroids uz2017 and wc2017 with comparable sensitivities. Because they are closer to Earth, we place upper limits on transmitter power to be 0.1 and 0.001 times the limits for 'Oumuamua. A concurrent set of observations over the same frequency range were made with a narrow-band (1 Hz) beamformer/spectrometer. Setting a 6.5 sigma threshold, the (frequency dependent) sensitivity limits on 'Oumuamua were in the range 175 +/- 25 Jy into a 1 Hz bin. This rules out 1 Hz transmitters on 'Oumuamua, 2017uz, and 2017wc to less than 500 mW, 50 mW, and 0.5 mW respectively over the frequency range from 1-10 GHz.

If Oumuamua was an Interstellar probe (the covert system survey intruder kind). Than would not expect any active sensors operating in wavelengths that could be pick up by the natives of the system the probe is heading into.

So as to not alarm the natives being observed as decreed by some Interstellar prime directive.  ;)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 09/19/2018 02:58 AM
Spin Evolution and Cometary Interpretation of the Interstellar Minor Object 1I/2017 'Oumuamua (https://arxiv.org/abs/1809.06389)

Observations of the first interstellar minor object 1I/2017 'Oumuamua did not reveal direct signs of outgassing that would have been natural if it had volatile-rich composition. However, a recent measurement by Micheli et al (2018) of a substantial non-gravitational acceleration affecting the orbit of this object has been interpreted as resulting from its cometary activity, which must be rather vigorous. Here we critically re-assess this interpretation by exploring the implications of measured non-gravitational acceleration for the 'Oumuamua's rotational state. We show that outgassing torques should drive rapid evolution of 'Oumuamua's spin (on a timescale of a few days), assuming torque asymmetry typical for the Solar System comets. However, given the highly elongated shape of the object, its torque asymmetry is likely higher, implying even faster evolution. This would have resulted in rapid rotational fission of 'Oumuamua during its journey through the Solar System and is clearly incompatible with the relative stability of its rotational state inferred from photometric variability. Based on these arguments, as well as the lack of direct signs of outgassing, we conclude that the classification of 'Oumuamua as a comet (invoked to explain its claimed anomalous acceleration) is questionable.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 09/25/2018 03:13 AM
Plausible home stars of the interstellar object 'Oumuamua found in Gaia DR2 (https://arxiv.org/abs/1809.09009)

The first detected interstellar object 'Oumuamua that passed within 0.25au of the Sun on 2017 September 9 was presumably ejected from a stellar system. We use its newly determined non-Keplerian trajectory together with the reconstructed Galactic orbits of 7 million stars from Gaia DR2 to identify past close encounters. Such an "encounter" could reveal the home system from which 'Oumuamua was ejected. The closest encounter, at 0.60pc (0.53-0.67pc, 90% confidence interval), was with the M2.5 dwarf HIP 3757 at a relative velocity of 24.7km/s, 1Myr ago. A more distant encounter (1.6pc) but with a lower encounter (ejection) velocity of 10.7km/s was with the G5 dwarf HD 292249, 3.8Myr ago. Two more stars have encounter distances and velocities intermediate to these. The encounter parameters are similar across six different non-gravitational trajectories for 'Oumuamua. Ejection of 'Oumuamua by scattering from a giant planet in one of the systems is plausible, but requires a rather unlikely configuration to achieve the high velocities found. A binary star system is more likely to produce the observed velocities. None of the four home candidates have published exoplanets or are known to be binaries. Given that the 7 million stars in Gaia DR2 with 6D phase space information is just a small fraction of all stars for which we can eventually reconstruct orbits, it is a priori unlikely that our current search would find 'Oumuamua's home star system. As 'Oumuamua is expected to pass within 1pc of about 20 stars and brown dwarfs every Myr, the plausibility of a home system depends also on an appropriate (low) encounter velocity.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 09/25/2018 06:40 AM
Spin Evolution and Cometary Interpretation of the Interstellar Minor Object 1I/2017 'Oumuamua (https://arxiv.org/abs/1809.06389)

Observations of the first interstellar minor object 1I/2017 'Oumuamua did not reveal direct signs of outgassing that would have been natural if it had volatile-rich composition. However, a recent measurement by Micheli et al (2018) of a substantial non-gravitational acceleration affecting the orbit of this object has been interpreted as resulting from its cometary activity, which must be rather vigorous. Here we critically re-assess this interpretation by exploring the implications of measured non-gravitational acceleration for the 'Oumuamua's rotational state. We show that outgassing torques should drive rapid evolution of 'Oumuamua's spin (on a timescale of a few days), assuming torque asymmetry typical for the Solar System comets. However, given the highly elongated shape of the object, its torque asymmetry is likely higher, implying even faster evolution. This would have resulted in rapid rotational fission of 'Oumuamua during its journey through the Solar System and is clearly incompatible with the relative stability of its rotational state inferred from photometric variability. Based on these arguments, as well as the lack of direct signs of outgassing, we conclude that the classification of 'Oumuamua as a comet (invoked to explain its claimed anomalous acceleration) is questionable.

So they are back to thinking it’s not a comet and not having a reason for its acceleration?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 10/20/2018 04:59 AM
https://www.cfa.harvard.edu/news/su201842

Quote

The IRAC camera on the Spitzer Space Telescope is currently about 155 million miles from Earth, and had a very different viewing angle toward 'Oumuamua than did Earth-bound telescopes. CfA astronomers Joe Hora, Howard Smith and Giovanni Fazio, together with their long-standing team of Near Earth Object scientists and other colleagues, pointed IRAC at the spot in the sky where predictions placed 'Oumuamua (because it is not bound to the Solar system and is so fast moving, 'Oumuamua’s path in the sky was comparatively difficult to calculate). After thirty hours of staring – a relatively long time – the object was not detected, and subsequent orbital analyses confirmed that the camera was pointed correctly towards it. The limit to its emission, however, was so low that it enabled the team to constrain some of its physical properties. The lack of an infrared signal, for example, suggests it has no gas or dust, species that would be expected if it were a cometary-like body. The scientists also calculate that, depending on its exact composition and reflectivity, 'Oumuamua is at least 240 meters (and maybe as much as one kilometer) in its longest dimension (for Star Trek aficionados, some fans estimate the length of the Enterprise to be 725 meters). The object has now moved too far for any of our telescopes to see it, and so although it will remain an interstellar mystery, it reminds us yet again that our cosmic neighborhood is full of surprises.
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 10/31/2018 08:46 PM
Speculation from a new scientific paper that Oumuamua could actually be an alien solar sail craft either an inactive relic or still active probe.

Here’s the paper in question.

Quote
“We explain the excess acceleration of `Oumuamua away from the Sun as the result of the force that the Sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimeter in thickness but tens of meters in size. This makes the object lightweight for its surface area and allows it to act as a light-sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the Solar System).”

Quote
“The alternative is to imagine that `Oumuamua was on a reconnaissance mission. The reason I contemplate the reconnaissance possibility is that the assumption that `Oumumua followed a random orbit requires the production of ~10^{15} such objects per star in our galaxy. This abundance is up to a hundred million times more than expected from the Solar System, based on a calculation that we did back in 2009. A surprisingly high overabundance, unless `Oumuamua is a targeted probe on a reconnaissance mission and not a member of a random population of objects.”

https://arxiv.org/pdf/1810.11490.pdf

Via this link.

https://www.universetoday.com/140391/could-oumuamua-be-an-extra-terrestrial-solar-sail/

This article adds further detail in reference to another new paper.

Quote
Just as I was publishing this I learned of a paper by Eric Mamajek (University of Rochester), who notes that ‘Oumuamua appears to have originated at the Local Standard of Rest (LSR), which is the galactic frame of reference. Quoting Mamajek: “Compared to the LSR, ‘Oumuamua has negligible radial and vertical Galactic motion…” According to Dr. Loeb in a subsequent email, less than one star in 500 is at that frame of reference to the same precision. (The Mamajek paper, “Kinematics of the Interstellar Vagabond 1I/’Oumuamua (A/2017 U1),” can be found here (https://arxiv.org/abs/1710.11364)
in preprint form)

Quote
It’s an interesting point. If ‘Oumuamua turned out to be artificial, would there be an advantage in such a position? Perhaps so, for as Loeb goes on to say in his email:

I view a sail (like `Oumuamua) floating in interstellar space with stars (like the Sun) running into it as if it were a buoy floating on the ocean surface with boats colliding with it. An artificial origin would naturally place floating sails at the LSR, perhaps as relay stations.

https://www.centauri-dreams.org/2018/10/29/on-oumuamua-thin-films-and-lightsails/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Bynaus on 11/01/2018 05:16 AM
Also, the recent suggestion that we have missed an interstellar comet a couple of years ago: https://arxiv.org/abs/1810.12766 That one, at least, seems a fit to our expectation for interstellar objects. In contrast to 'Oumuamua, I mean.
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/01/2018 06:32 AM
It wouldn’t surprise me if we don’t discover in the longer term there is a veritable  “highway” of interstellar material passing through the solar system. I believe from the papers posted on here that even at our current level of technology we should expect to detect one interstellar visitor per year.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ThereIWas3 on 11/01/2018 04:40 PM
Speculation from a new scientific paper

That paper was quite detailed (3 pages of equations) and carefully explains why the other explanations do not hold together but that their "light sail" hyposthesis is a good fit.  But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.  Still, that is an awfully small number, and I wonder how that was measured.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/01/2018 05:53 PM
Speculation from a new scientific paper

That paper was quite detailed (3 pages of equations) and carefully explains why the other explanations do not hold together but that their "light sail" hyposthesis is a good fit.  But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.  Still, that is an awfully small number, and I wonder how that was measured.

My use of the word was inline of the idea that extraordinary claims need extraordinary evidence.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Welsh Dragon on 11/01/2018 06:01 PM
Speculation from a new scientific paper

That paper was quite detailed (3 pages of equations) and carefully explains why the other explanations do not hold together but that their "light sail" hyposthesis is a good fit.  But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.  Still, that is an awfully small number, and I wonder how that was measured.
It's not even speculation from a scientific paper. It's speculation from an unreviewed manuscript. Rather important difference.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: speedevil on 11/01/2018 07:00 PM
Speculation from a new scientific paper

That paper was quite detailed (3 pages of equations) and carefully explains why the other explanations do not hold together but that their "light sail" hyposthesis is a good fit.  But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.  Still, that is an awfully small number, and I wonder how that was measured.
It's not even speculation from a scientific paper. It's speculation from an unreviewed manuscript. Rather important difference.

Indeed, it means that two guys haven't looked at some of it and noticed no major problems with the bits they read.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Bynaus on 11/01/2018 07:44 PM
Quote
But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.

Hm, 4.92 x 10-4 cm s-2 is the same as 4.92 x 10-6 m s-2. Note cm vs. m.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: as58 on 11/01/2018 08:31 PM
Speculation from a new scientific paper

That paper was quite detailed (3 pages of equations) and carefully explains why the other explanations do not hold together but that their "light sail" hyposthesis is a good fit.  But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.  Still, that is an awfully small number, and I wonder how that was measured.
It's not even speculation from a scientific paper. It's speculation from an unreviewed manuscript. Rather important difference.

Indeed, it means that two guys haven't looked at some of it and noticed no major problems with the bits they read.

In astronomy usually just one guy...
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Mongo62 on 11/02/2018 12:53 AM
Origin of 1I/'Oumuamua. II. An ejected exo-Oort cloud object? (https://arxiv.org/abs/1811.00023)

1I/'Oumuamua is the first detected interstellar interloper. We test the hypothesis that it is representative of a background population of exo-Oort cloud objects ejected under the effect of post-main sequence mass loss and stellar encounters. We do this by comparing the cumulative number density of interstellar objects inferred from the detection of 1I/'Oumuamua to that expected from these two clearing processes. We consider the 0.08--8 M⊙ mass range, take into account the dependencies with stellar mass, Galactocentric distance, and evolutionary state, and consider a wide range of size distributions for the ejected objects. Our conclusion is that 1I/'Oumuamua is likely not representative of this background population, strengthened by the consideration that our estimate is likely an overestimate because it assumes exo-Oort clouds are frequent but the parameter space to form them is actually quite restricted. We discuss whether the number density of free-floating, planetary-mass objects derived from gravitational microlensing surveys could be used as a discriminating measurement regarding 1I/'Oumuamua's origin (given their potential common origin). We conclude that this is challenged by the mass limitation of the surveys and the resulting uncertainty of the mass distribution. The detection of interlopers may be one of the few observational constraints of the low end of the mass distribution of free-floaters, with the caveat that, as we conclude here and in Moro-Mart\'ın (2018), it might not be appropriate to assume they are representative of an isotropic background population, which makes the derivation of a number density very challenging.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/04/2018 03:58 PM
I am posting this as it appears to have some additional commentary from Prof. Loeb about his paper as quoted below.

Quote
“We explain the excess acceleration of `Oumuamua away from the Sun as the result of the force that the Sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimeter in thickness but tens of meters in size. This makes the object lightweight for its surface area and allows it to act as a light-sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the Solar System).”

Quote
“The alternative is to imagine that `Oumuamua was on a reconnaissance mission. The reason I contemplate the reconnaissance possibility is that the assumption that `Oumumua followed a random orbit requires the production of ~10^{15} such objects per star in our galaxy. This abundance is up to a hundred million times more than expected from the Solar System, based on a calculation that we did back in 2009. A surprisingly high overabundance, unless `Oumuamua is a targeted probe on a reconnaissance mission and not a member of a random population of objects.”

https://www.universetoday.com/140391/could-oumuamua-be-an-extra-terrestrial-solar-sail/
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ThereIWas3 on 11/04/2018 05:17 PM
The problem with that analysis is that you can not extrapolate the random abundance of such objects from a single encounter.  There might have been more, but we missed them - we very nearly missed detecting this one.  There might be just the one, literally with our name on it.  Or there might be just the one, and we just happened to run into it.

I'm walking down the sidewalk and find a dime on the ground, which I pick up.  From this one event can I calculate how many dimes there are on all the city sidewalks?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: speedevil on 11/04/2018 07:10 PM
I'm walking down the sidewalk and find a dime on the ground, which I pick up.  From this one event can I calculate how many dimes there are on all the city sidewalks?
Yes.
You can reasonably say things about the probabilities involved, on the assumption that the events are uncorrelated and random.

On the street example - if you walk down the same route every day, and on the hundredth day you find a dime, the chances of the average rate of dimes being one a day in the parts you walk down is essentially zero.

Seeing it after a hundred days means that the probability of occurrance is most likely around a hundred days.

It pretty firmly rules out it being anything under about 10, though it does not place strong constraints on what the upper limit is.

We know where various telescopes were pointing, and what data was taken, and people have computed from this good maximum rates on how many objects on such extreme orbits we could have missed.

At some point, you have to rely on the universe not to throw you a stacked deck.
If you flip a coin a hundred times and get 40 heads and 60 tails, it's reasonable to conclude it may be a fair coin.
If the first time you do this, you get a hundred heads, something odd is going on.

For the time to first occurance not to tell you anything pretty much implies that something odd is going on - which is itself interesting.
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/04/2018 07:16 PM
One of the biggest problems was that one of our best resources for studying this had been taken offline by storm damage.

Source for that statement is this new video on the topic by Seeker.

https://www.youtube.com/watch?v=Wflp1fQKY5w
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: TakeOff on 11/04/2018 10:27 PM
I'm walking down the sidewalk and find a dime on the ground, which I pick up.  From this one event can I calculate how many dimes there are on all the city sidewalks?
If Laplace's Sunrise problem is applicable, and k is the number of searches having been made, none of them finding this, then the probability that the next search also won't find it, is (k+1)/(k+2). After for example nine searches finding nothing, the probability for the next attempt also finding nothing, is (9+1)/(9+2)=91%.

Is that right?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/06/2018 06:01 PM
So regarding the claim of non-gravitational acceleration of Oumuamua, what are the possible natural explanations for this?
Some people have said there may be some hidden outgassing, even though the object did not appear to have a cometary tail. How can that happen?

Even though there's no way to catch up with the object to view it directly, could it be feasible to send a probe along its "exhaust trail" to detect evidence of the outgassing? How long do such trails last before all traces are lost?

Is there any other way to look for the outgassing?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: TakeOff on 11/06/2018 06:32 PM
If all volatilities and small particle dust have been removed by cooking in interstellar space, or whatever ejecting close stellar encounter this guy has been through, then our Sun would only have particles on its surface to excite with its rays, that aren't detectable in infrared. So not out gassing, but out dusting. And I don't make this stuff up. I watched on my crystal screen someone who looked like he or she knew something about it, proposing this. Someone with a beard between the knees at one altitude or the other.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/06/2018 06:50 PM
If all volatilities and small particle dust have been removed by cooking in interstellar space, or whatever ejecting close stellar encounter this guy has been through, then our Sun would only have particles on its surface to excite with its rays, that aren't detectable in infrared. So not out gassing, but out dusting. And I don't make this stuff up. I watched on my crystal screen someone who looked like he or she knew something about it, proposing this. Someone with a beard between the knees at one altitude or the other.


Never heard of dust as a means of propulsion before. What kind of Isp do you get from solar-heated dust?

Has this phenomenon ever previously been observed for other objects in our solar system?

Could that dust remain for awhile as a sort of contrail?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/06/2018 07:30 PM
If all volatilities and small particle dust have been removed by cooking in interstellar space, or whatever ejecting close stellar encounter this guy has been through, then our Sun would only have particles on its surface to excite with its rays, that aren't detectable in infrared. So not out gassing, but out dusting. And I don't make this stuff up. I watched on my crystal screen someone who looked like he or she knew something about it, proposing this. Someone with a beard between the knees at one altitude or the other.

Sounds rather unlikely. The Solar Sail explanation seems more likely than that.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/06/2018 09:48 PM
Sounds rather unlikely. The Solar Sail explanation seems more likely than that.

Regarding this Solar Sail speculation - I thought this thing was supposed to be cigar-shaped - how can something that's cigar-shaped amount to a Solar Sail?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/06/2018 10:04 PM
Sounds rather unlikely. The Solar Sail explanation seems more likely than that.

Regarding this Solar Sail speculation - I thought this thing was supposed to be cigar-shaped - how can something that's cigar-shaped amount to a Solar Sail?

Good question I have been wondering if their theory brings into question the speculated shape of the object?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Comga on 11/06/2018 10:17 PM
Sounds rather unlikely. The Solar Sail explanation seems more likely than that.

Regarding this Solar Sail speculation - I thought this thing was supposed to be cigar-shaped - how can something that's cigar-shaped amount to a Solar Sail?

IIRC the "cigar shape" is a conjecture to account for the large periodic variation in intrinsic brightness.
It's a simple shape whose area can change by an order of magnitude depending on the direction of observation.
It has also been portrayed, in the Meech TED talk I believe, as sort of a rough disk, which could also have a 10:1 ratio.
A solar sail could have an enormous ratio if it were pitching or rolling.
If its plane sweeps over the observer the cross section becomes tiny.
That could make too large a variation.  Oumaumau doesn't disappear at its faintest.
And the variation in the angle of observation from Earth could change the ratio over time unless the motion was in a specific orientation in space.
But a pitching solar sail wouldn't be an efficient way to gain velocity.
I think the "solar sail" hypothesis is based solely on the apparent acceleration.
But I could well be wrong.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/06/2018 10:18 PM
Sounds rather unlikely. The Solar Sail explanation seems more likely than that.

Regarding this Solar Sail speculation - I thought this thing was supposed to be cigar-shaped - how can something that's cigar-shaped amount to a Solar Sail?

Good question I have been wondering if their theory brings into question the speculated shape of the object?

You can read their paper here: https://arxiv.org/abs/1810.11490
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ThereIWas3 on 11/07/2018 01:35 AM
I did not think the shape was observed directly, but was hypothesized based off the fluctuations in brightness.  Of course that assumes uniform reflectivity, which might not be the case.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Comga on 11/07/2018 02:03 AM
If all volatilities and small particle dust have been removed by cooking in interstellar space, or whatever ejecting close stellar encounter this guy has been through, then our Sun would only have particles on its surface to excite with its rays, that aren't detectable in infrared. So not out gassing, but out dusting. And I don't make this stuff up. I watched on my crystal screen someone who looked like he or she knew something about it, proposing this. Someone with a beard between the knees at one altitude or the other

Never heard of dust as a means of propulsion before. What kind of Isp do you get from solar-heated dust?

Has this phenomenon ever previously been observed for other objects in our solar system?
(snip)

Isp is the exhaust velocity divided by Earth's gravity, which in Imperial units, with pounds of mass "cancelling" pounds of force, comes out in seconds.

So if the dust is expelled from heat, even sublimating ice, it would be really low.
But if the mechanism was something else, like electrostatic repulsion after charge generation from solar ultraviolet or charged particles, and the dust was very fine, it could be significant.

I did a calculation like this once, where the kinetic energy of atoms from an ion engine exhaust was transferred to dust particles.  It increased the momentum transfer by about six orders of magnitude.

As to your second question, that's the nature of comets, how Whipple deduced that they were composed of ice.
That doesn't seem to work for Oumuamua, which didn't have observable tails or coma.

edit: (Hawaiian) spelling error
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/07/2018 03:34 PM
I wonder if the speculated ejected dust could be interstellar matter which accumulated / condensed / accreted on the object across its long voyage through interstellar space?


So if the dust is expelled from heat, even sublimating ice, it would be really low.
But if the mechanism was something else, like electrostatic repulsion after charge generation from solar ultraviolet or charged particles, and the dust was very fine, it could be significant.

I did a calculation like this once, where the kinetic energy of atoms from an ion engine exhaust was transferred to dust particles.  It increased the momentum transfer by about six orders of magnitude.

I've never heard about dust improving the performance of ion engines. Has this ever been studied?

So does that mean ion engines would work better when traveling through a dust cloud, as compared to traveling through a vacuum?
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/07/2018 06:42 PM
I’d be kind of unlucky in the extreme if this was an alien vehicle, and we can never know that partly because we missed it initially on its inward trip. And partly because we just don’t have the technology to give us the data to know for sure.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: TakeOff on 11/07/2018 06:58 PM
When Cassini (the great scientist, not the great machine) discovered Iapetus, moon of Saturn, he could only observe it while on one side of Saturn, never on the other side. Did it turn around and come back every half orbit? A perfectly reasonable hypothesis for all that was known at the time. Except for orbital mechanics. Was it an alien spacecraft? But he intelligently proposed that one half of it was bright, and the other hemisphere dark. And that's so. The hypothesis of the extreme elongation of Ouma is based on what's known about asteroids and comets in the Solar system. But since Ouma has been ejected from the stellar formation process where it once formed, perhaps it has been badly burned on one side when passing close to the star (perhaps in a binary system) that ejected it. The spacecraft people need to temper their Hollywood fantasies. Why would a spacecraft do what Ouma did? A pretty boring mission if so. Something is malfunctioning here, one doesn't have to go interstellar to realize that.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/07/2018 08:06 PM
When Cassini (the great scientist, not the great machine) discovered Iapetus, moon of Saturn, he could only observe it while on one side of Saturn, never on the other side. Did it turn around and come back every half orbit? A perfectly reasonable hypothesis for all that was known at the time. Except for orbital mechanics. Was it an alien spacecraft? But he intelligently proposed that one half of it was bright, and the other hemisphere dark. And that's so. The hypothesis of the extreme elongation of Ouma is based on what's known about asteroids and comets in the Solar system. But since Ouma has been ejected from the stellar formation process where it once formed, perhaps it has been badly burned on one side when passing close to the star (perhaps in a binary system) that ejected it. The spacecraft people need to temper their Hollywood fantasies. Why would a spacecraft do what Ouma did? A pretty boring mission if so. Something is malfunctioning here, one doesn't have to go interstellar to realize that.

Your post makes no sense as it in-fact did exactly what a probe would do being as it went straight through the habitable zone of this solar system.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: TakeOff on 11/07/2018 08:11 PM
When Cassini (the great scientist, not the great machine) discovered Iapetus, moon of Saturn, he could only observe it while on one side of Saturn, never on the other side. Did it turn around and come back every half orbit? A perfectly reasonable hypothesis for all that was known at the time. Except for orbital mechanics. Was it an alien spacecraft? But he intelligently proposed that one half of it was bright, and the other hemisphere dark. And that's so. The hypothesis of the extreme elongation of Ouma is based on what's known about asteroids and comets in the Solar system. But since Ouma has been ejected from the stellar formation process where it once formed, perhaps it has been badly burned on one side when passing close to the star (perhaps in a binary system) that ejected it. The spacecraft people need to temper their Hollywood fantasies. Why would a spacecraft do what Ouma did? A pretty boring mission if so. Something is malfunctioning here, one doesn't have to go interstellar to realize that.

Your post makes no sense as it in-fact did exactly what a probe would do being as it went straight through the habitable zone of this solar system.
You are extremely geocentric!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Tywin on 11/07/2018 08:42 PM
If somebody want to sign  :D

https://www.change.org/p/agencias-espaciales-sonda-a-oumuamua/u/23558137
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/07/2018 09:13 PM

A solar sail could have an enormous ratio if it were pitching or rolling.
...
But a pitching solar sail wouldn't be an efficient way to gain velocity.
I think the "solar sail" hypothesis is based solely on the apparent acceleration.
But I could well be wrong.

But so even if this object was doing the conventional outgassing of a comet, or even that out-dusting mentioned before - wouldn't its pitching motion affect the direction of thrust? Even if the sunlight is always hitting it from the same direction, wouldn't the resultant outgassing keep changing orientation with the object itself?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Comga on 11/07/2018 09:23 PM
I wonder if the speculated ejected dust could be interstellar matter which accumulated / condensed / accreted on the object across its long voyage through interstellar space?


So if the dust is expelled from heat, even sublimating ice, it would be really low.
But if the mechanism was something else, like electrostatic repulsion after charge generation from solar ultraviolet or charged particles, and the dust was very fine, it could be significant.

I did a calculation like this once, where the kinetic energy of atoms from an ion engine exhaust was transferred to dust particles.  It increased the momentum transfer by about six orders of magnitude.

I've never heard about dust improving the performance of ion engines. Has this ever been studied?

So does that mean ion engines would work better when traveling through a dust cloud, as compared to traveling through a vacuum?

The Bialy & Loeb paper discusses the accumulation of ISM dust on the surface of 'Oumuamua.

No.  Ion engines don't gain from traveling through dust, but that's going off topic here. 

The relevant point was that if dust is liberated by some mechanism much more energetic than heating it might be possible to increase the momentum transfer, the thrust, Isp as you put it, which would increase Bialy's thickness solution.  It would also increase the range of origin distances, as the lifetime would not be limited by erosion of a sub-millimeter thick "sail".

Quote
“We explain the excess acceleration of `Oumuamua away from the Sun as the result of the force that the Sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimeter in thickness but tens of meters in size.”

emphasis mine

The momentum transfer mechanism would need to increase by something like five orders of magnitude to get from 0.3-0.9 mm to something that could easily be natural, like 30-90 meters. 
That may be physical, as photons don't carry much momentum.
Something like electrostatic repulsion of fine dust particles might do that.

However tempting, "aliens" should be the last hypothesis. 
And we almost never run out of hypothesis.
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/07/2018 09:26 PM
I wonder if the speculated ejected dust could be interstellar matter which accumulated / condensed / accreted on the object across its long voyage through interstellar space?


So if the dust is expelled from heat, even sublimating ice, it would be really low.
But if the mechanism was something else, like electrostatic repulsion after charge generation from solar ultraviolet or charged particles, and the dust was very fine, it could be significant.

I did a calculation like this once, where the kinetic energy of atoms from an ion engine exhaust was transferred to dust particles.  It increased the momentum transfer by about six orders of magnitude.

I've never heard about dust improving the performance of ion engines. Has this ever been studied?

So does that mean ion engines would work better when traveling through a dust cloud, as compared to traveling through a vacuum?

The Bialy & Loeb paper discusses the accumulation of ISM dust on the surface of 'Oumuamua.

No.  Ion engines don't gain from traveling through dust, but that's going off topic here. 

The relevant point was that if dust is liberated by some mechanism much more energetic than heating it might be possible to increase the momentum transfer, the thrust, Isp as you put it, which would increase Bialy's thickness solution.  It would also increase the range of origin distances, as the lifetime would not be limited by erosion of a sub-millimeter thick "sail".

The ejection mechanism would need to be something like five orders of magnitude to get from 0.3-0.9 mm to something that could be natural, like 30-90 meters.  That may be physical, as photons don't carry much momentum.

However tempting, "aliens" should be the last hypothesis.

Your last sentence is why there has been inherent and persistent bias against SETI research up until very recently.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Comga on 11/07/2018 09:42 PM
Your post makes no sense as it in-fact did exactly what a probe would do being as it went straight through the habitable zone of this solar system.
You are extremely geocentric!

Agreed
Logical fallacy:
We have observed an interstellar transit
We can only observe transits through our solar system
Our solar system is inhabited
So our solar system is habitable
So the observed transit was of a habitable system
Therefore all interstellar transits are of habitable systems
Therefore they are intelligently directed
Therefore it is intelligently directed

There's a gap in that chain.

Your last sentence is why there has been inherent and persistent bias against SETI research up until very recently.
Not really.
I probably have more credits than you on [email protected]  (4E6 seconds?)
They don't jump up and down whenever anything is 3-sigma greater than the noise.
Yet we keep looking.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/07/2018 10:10 PM
It never fails to disappoint me that "an unusual object has properties that look suspiciously artificial and we cannot disprove that hypothesis with the data we have" consistently results in retorts along the lines of "it's not aliens, and you've done a bad thing by even suggesting the possibility."
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: whitelancer64 on 11/07/2018 10:28 PM
It never fails to disappoint me that "an unusual object has properties that look suspiciously artificial and we cannot disprove that hypothesis with the data we have" consistently results in retorts along the lines of "it's not aliens, and you've done a bad thing by even suggesting the possibility."

It's not clear that it's an unnatural activity, though. It took decades to figure out that the Pioneer Anomaly was re-radiated heat from the RTGs.

Saying "we don't know right now" doesn't automatically mean that the default explanation must be that it's aliens.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/07/2018 10:33 PM
It's not clear that it's an unnatural activity, though. It took decades to figure out that the Pioneer Anomaly was re-radiated heat from the RTGs.

Saying "we don't know right now" doesn't automatically mean that the default explanation must be that it's aliens.

What purpose does restating this actually serve, though? Obviously if someone pipes in that it must be aliens, they need to be warned that they're getting much too far ahead of themselves, but that argument is not only consistently preempted, but anyone who tries to continue the line of discussion is treated as if they just declared that the observed phenomenon is a definitive work of extra-terrestrial intelligence.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: whitelancer64 on 11/07/2018 10:54 PM
It's not clear that it's an unnatural activity, though. It took decades to figure out that the Pioneer Anomaly was re-radiated heat from the RTGs.

Saying "we don't know right now" doesn't automatically mean that the default explanation must be that it's aliens.

What purpose does restating this actually serve, though? Obviously if someone pipes in that it must be aliens, they need to be warned that they're getting much too far ahead of themselves, but that argument is not only consistently preempted, but anyone who tries to continue the line of discussion is treated as if they just declared that the observed phenomenon is a definitive work of extra-terrestrial intelligence.

What's the point of talking about it being aliens when alternative explanations haven't been explored?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/07/2018 10:59 PM
What's the point of talking about it being aliens when alternative explanations haven't been explored?

What alternative explanations in the problem space currently strike you as inadequately explored? The only reason aliens are being raised right now is because Oumuamua passed very close to the Earth, has exhibited unexplained acceleration, has physical dimensions unlike anything ever seen, and passed through from an unexpected trajectory that does not oblige an obvious point of origin.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: whitelancer64 on 11/07/2018 11:13 PM
What's the point of talking about it being aliens when alternative explanations haven't been explored?

What alternative explanations in the problem space currently strike you as inadequately explored? The only reason aliens are being raised right now is because Oumuamua passed very close to the Earth, has exhibited unexplained acceleration, has physical dimensions unlike anything ever seen, and passed through from an unexpected trajectory that does not oblige an obvious point of origin.

Any, as it hasn't been adequately explored at all. Why do you insist on defending jumping to the conclusion that it must be aliens?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/07/2018 11:41 PM
Any, as it hasn't been adequately explored at all. Why do you insist on defending jumping to the conclusion that it must be aliens?

I'm not, and am making no such defense, which is the entire object of my frustration!
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: matthewkantar on 11/08/2018 12:54 AM
What's the point of talking about it being aliens when alternative explanations haven't been explored?

What alternative explanations in the problem space currently strike you as inadequately explored? The only reason aliens are being raised right now is because Oumuamua passed very close to the Earth, has exhibited unexplained acceleration, has physical dimensions unlike anything ever seen, and passed through from an unexpected trajectory that does not oblige an obvious point of origin.

-it didn't pass close enough to suggest a targeted flyby.
-the acceleration is very small if it exists at all.
-the dimensions are inferred from dimming, many other explanation possible.
-what is unexpected about the trajectory of a sample of one object?

Squeezing the data will not make it more likely to be an alien artifact.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/08/2018 01:24 AM
What's the point of talking about it being aliens when alternative explanations haven't been explored?

What alternative explanations in the problem space currently strike you as inadequately explored? The only reason aliens are being raised right now is because Oumuamua passed very close to the Earth, has exhibited unexplained acceleration, has physical dimensions unlike anything ever seen, and passed through from an unexpected trajectory that does not oblige an obvious point of origin.

-it didn't pass close enough to suggest a targeted flyby.
-the acceleration is very small if it exists at all.
-the dimensions are inferred from dimming, many other explanation possible.
-what is unexpected about the trajectory of a sample of one object?

Squeezing the data will not make it more likely to be an alien artifact.

Oumuamua passed within 60 million kilometers of the Earth from interstellar distances.
The acceleration never the less does not have a good explanation at this time.
Light curve modeling is not an unreliable technique for general inference
There are very few stars in plane with Oumuamua, and all of them are many parsecs away.

Squeezing the data is not necessary to say that it is peculiar, or that Oumuamua implies significantly more interstellar objects than observed.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: jebbo on 11/08/2018 06:08 AM
[ snippety snip ]
There are very few stars in plane with Oumuamua, and all of them are many parsecs away.

Squeezing the data is not necessary to say that it is peculiar, or that Oumuamua implies significantly more interstellar objects than observed.

On the point of origin and population size, 'Oumuamua was VERY close to galactic LSR and came from the solar apex.  This is suggestive of a very old population orbiting the galactic core ...

Poor thing, minding its own business, slowly circling the galaxy and along comes this pesky Solar System disturbing it and firing it off in some random direction ;)

--- Tony
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/08/2018 06:45 AM
Your post makes no sense as it in-fact did exactly what a probe would do being as it went straight through the habitable zone of this solar system.
You are extremely geocentric!

Agreed
Logical fallacy:
We have observed an interstellar transit
We can only observe transits through our solar system
Our solar system is inhabited
So our solar system is habitable
So the observed transit was of a habitable system
Therefore all interstellar transits are of habitable systems
Therefore they are intelligently directed
Therefore it is intelligently directed

There's a gap in that chain.

Your last sentence is why there has been inherent and persistent bias against SETI research up until very recently.
Not really.
I probably have more credits than you on [email protected]  (4E6 seconds?)
They don't jump up and down whenever anything is 3-sigma greater than the noise.
Yet we keep looking.

And I follow Jason Wright’s Twitter and he has mentioned this issue more than once regarding SETI, and I know who I am more likely to believe on this matter.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: TakeOff on 11/08/2018 08:23 AM
Extremely ...centric was intended as a pun. Exorbitant objects require extraordinary claims.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Bynaus on 11/08/2018 09:27 AM
Its highly probable that it is not aliens (as always).

However, if, while trying to understand this object, we find that its properties can be explained in a straightforward way by it being very thin and light, which might or might not suggest an artificial origin - why should we not be allowed to have a reasonable discussion about a potential artificial origin in this context?

Mind you, it would be totally unscientific if someone had said "well that force pushing it from a keplerian path is just its hyperdrive in standby". This would be a laughable "god of the gaps"-type explanation that explains nothing. But this is not what happend!

The problem is not the scientists being unscientific with their proposal. Thinking outside the box is something that should come natural to any scientist, actually, and it should be fully acceptable to ponder and drop also seemingly exotic explanations when looking for an answer.

The actual problem is the internet being highly disfunctional as a place to have a reasonable discussion between educated adults, because on the internet, money is earned by attention, and scientists talking of aliens always brings attention. A harmless "Hey, look at that data set, isn't that weird? I wonder what it could mean!" quickly turns into "Scientists find definitive proof of alien spaceship, NASA cover-up underway" (literally!).

But that is not really the scientists fault.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/08/2018 10:08 AM
The variable brightness on this object is believed to be due to a tumbling motion and a high aspect ratio.

With ordinary comets which have the visible tail, do any of them exhibit any tumbling motion?

Could it be that Oumuamua's tumbling is the reason why it doesn't have a visible tail?
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/08/2018 12:41 PM
Its highly probable that it is not aliens (as always).

However, if, while trying to understand this object, we find that its properties can be explained in a straightforward way by it being very thin and light, which might or might not suggest an artificial origin - why should we not be allowed to have a reasonable discussion about a potential artificial origin in this context?

Mind you, it would be totally unscientific if someone had said "well that force pushing it from a keplerian path is just its hyperdrive in standby". This would be a laughable "god of the gaps"-type explanation that explains nothing. But this is not what happend!

The problem is not the scientists being unscientific with their proposal. Thinking outside the box is something that should come natural to any scientist, actually, and it should be fully acceptable to ponder and drop also seemingly exotic explanations when looking for an answer.

The actual problem is the internet being highly disfunctional as a place to have a reasonable discussion between educated adults, because on the internet, money is earned by attention, and scientists talking of aliens always brings attention. A harmless "Hey, look at that data set, isn't that weird? I wonder what it could mean!" quickly turns into "Scientists find definitive proof of alien spaceship, NASA cover-up underway" (literally!).

But that is not really the scientists fault.

I can’t say I’ve seen that much this means definitive proof of aliens in its coverage online, but then I don’t go looking for rubbish coverage of it online and then rail against the internet for its inequity. Because of course it’s always the internet and not scientists courting attention or some other part of the human condition. I think some think people forget scientists are still people with all that entails, and your post is a perfect example of this and the idealisation of scientists which I would argue is just as damaging as mangled messages online to science communication.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Bynaus on 11/08/2018 02:47 PM
Its highly probable that it is not aliens (as always).

However, if, while trying to understand this object, we find that its properties can be explained in a straightforward way by it being very thin and light, which might or might not suggest an artificial origin - why should we not be allowed to have a reasonable discussion about a potential artificial origin in this context?

Mind you, it would be totally unscientific if someone had said "well that force pushing it from a keplerian path is just its hyperdrive in standby". This would be a laughable "god of the gaps"-type explanation that explains nothing. But this is not what happend!

The problem is not the scientists being unscientific with their proposal. Thinking outside the box is something that should come natural to any scientist, actually, and it should be fully acceptable to ponder and drop also seemingly exotic explanations when looking for an answer.

The actual problem is the internet being highly disfunctional as a place to have a reasonable discussion between educated adults, because on the internet, money is earned by attention, and scientists talking of aliens always brings attention. A harmless "Hey, look at that data set, isn't that weird? I wonder what it could mean!" quickly turns into "Scientists find definitive proof of alien spaceship, NASA cover-up underway" (literally!).

But that is not really the scientists fault.

I can’t say I’ve seen that much this means definitive proof of aliens in its coverage online, but then I don’t go looking for rubbish coverage of it online and then rail against the internet for its inequity. Because of course it’s always the internet and not scientists courting attention or some other part of the human condition. I think some think people forget scientists are still people with all that entails, and your post is a perfect example of this and the idealisation of scientists which I would argue is just as damaging as mangled messages online to science communication.

FTR, I don't go looking for rubbish coverage, I think someone linked such an article in my twitter feed.

Sure, scientists are humans too. But a scientist has almost nothing to gain, and everything to lose for boasting about having found aliens (look at the backlash it produced). While for news websites (especially the ones without actual science writers), the more hype, the more money they make. Yep, even scientists can get on the wrong path sometimes, and yep, sometimes, even the yellow pages of internet produce well-balanced, fair articles about scientists talking about aliens. But since the incentives push strongly into the other direction, its usually the other way around.

My point was: science cannot have certain ideas tabooed or even censored just because they might create a hype on the internet. Tin-foil-hatters gonna tin-foil-hat, anyway.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: bad_astra on 11/08/2018 03:01 PM
The spacecraft people need to temper their Hollywood fantasies.
Why would an alien artifact or remote probe be a Hollywood fantasy. According to Drake's equation, it would not seem that fantastical at all. A reasonably advanced civilization would be expected to send out probes. We certainly do. I am more interested in why the idea that it COULD be artificial would make someone "spacecraft people." When did skepticism override logic?

one doesn't have to go interstellar to realize that.
you realize the irony in that statement, I take it?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: jebbo on 11/08/2018 03:08 PM
BTW its non-gravitational acceleration falls within the range for solar system objects.
 
https://twitter.com/astrokiwi/status/1060553406522253312?s=19 (https://twitter.com/astrokiwi/status/1060553406522253312)
Title: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/08/2018 03:37 PM
That chart says comets we don’t even know for certain it falls within that class of object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/09/2018 09:03 AM
Not everyone is on board with that wild Oumuamua ‘alien’ theory (https://bgr.com/2018/11/08/oumuamua-alien-spacecraft-theory-asteroid-comet/)

Quote
“The thing you have to understand is: scientists are perfectly happy to publish an outlandish idea if it has even the tiniest sliver of a chance of not being wrong,” astrophysicist Katie Mack noted in a thread on Twitter. “Some of us are more conservative, of course. And it surely varies by field. But in my area (astrophysics/cosmology), there’s generally no downside to publishing something that’s (a) somehow interesting and (b) not completely ruled out, whether or not it ends up ‘the right answer.'”

She’s not alone, and other scientists have weighed in with their own doubts about the theory. Put simply, there’s no real smoking gun that screams “aliens!” but there’s also not much to prove that it isn’t. The result is a theory that sounds groundbreaking and incredible, but is almost certainly nothing more than a dream.

Scientists push back against Harvard 'alien spacecraft' theory (https://m.phys.org/news/2018-11-scientists-harvard-alien-spacecraft-theory.html)

Quote
"Like most scientists, I would love there to be convincing evidence of alien life, but this isn't it," said Alan Fitzsimmons, an astrophysicist at Queens University, Belfast.

"It has already been shown that its observed characteristics are consistent with a comet-like body ejected from another star system," he told AFP.

"And some of the arguments in this study are based on numbers with large uncertainties."
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ChrisWilson68 on 11/09/2018 10:23 AM
I'm walking down the sidewalk and find a dime on the ground, which I pick up.  From this one event can I calculate how many dimes there are on all the city sidewalks?
Yes.
You can reasonably say things about the probabilities involved, on the assumption that the events are uncorrelated and random.

On the street example - if you walk down the same route every day, and on the hundredth day you find a dime, the chances of the average rate of dimes being one a day in the parts you walk down is essentially zero.

Seeing it after a hundred days means that the probability of occurrance is most likely around a hundred days.

It's not that simple.

What if you would have wondered about the odds if you had found a penny, a nickel, a dime, or a quarter?  It might be that each is a one-in-four-hundred shot, so that, on average, you'd find one of the four every hundred or so times you took your walk.

But it's much worse than that because you have to consider all the possible outcomes that would strike you as interesting enough to wonder about the odds.  If there are a ten million different things that are so odd that you'd notice them and wonder about the odds, and each was a one-in-a-billion shot, then on average every hundred or so walks you'd encounter one of them, wonder about it, and think that that particular thing was a one-in-a-hundred shot when it was actually one in a billion.  What's the one in a hundred shot is anything in the space of things that would make you wonder.

Astronomers look at a lot of things in a lot of places.  If they see something that makes you go "hmm", you need to consider all the different things all our thousands of astronomers could happen upon before you decide how unlikely you think that particular thing is.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ChrisWilson68 on 11/09/2018 10:24 AM
I'm walking down the sidewalk and find a dime on the ground, which I pick up.  From this one event can I calculate how many dimes there are on all the city sidewalks?
If Laplace's Sunrise problem is applicable, and k is the number of searches having been made, none of them finding this, then the probability that the next search also won't find it, is (k+1)/(k+2). After for example nine searches finding nothing, the probability for the next attempt also finding nothing, is (9+1)/(9+2)=91%.

Is that right?

No, that is not right.

The probability of the next attempt also finding nothing depends on the prior probability distribution you assume.  When people give formulas for these sorts of things, they are implicitly assuming something about the prior probability distribution.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: speedevil on 11/09/2018 01:05 PM
Astronomers look at a lot of things in a lot of places.  If they see something that makes you go "hmm", you need to consider all the different things all our thousands of astronomers could happen upon before you decide how unlikely you think that particular thing is.
This is a mostly broken argument.
This is not one of 'ten million things'.
This is within the top ten things you might rank as interesting given only a basic idea of cosmology, and no knowledge of your particular place.

'Are we an isolated body in the universe'
'What is that big light'
'What are those smaller lights that move'
'What are those small lights that do not move'
'are the small lights that do not move like the big light?'
'Are there smaller lights that move around them?'
'Are all the smaller lights around the bigger lights?'

Once you have discovered that there are bodies on highly eccentric orbits, and know there are stars, the very next thing you ask about is 'are all of these objects actually coming from our solar system'.

And we're pretty much interested in any object coming through, not bodies with the particular class of the topic object.

You are of course free to choose your prior, but if that prior is not 'uncorrelated objects' - you're going to have to justify that really hard to be taken seriously when arguing the actual occurrance rate is much below the one implied by one object seen after a decade or so of observations that could have seen it.

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: TakeOff on 11/09/2018 02:21 PM
The spacecraft people need to temper their Hollywood fantasies.
Why would an alien artifact or remote probe be a Hollywood fantasy. According to Drake's equation, it would not seem that fantastical at all. A reasonably advanced civilization would be expected to send out probes. We certainly do. I am more interested in why the idea that it COULD be artificial would make someone "spacecraft people." When did skepticism override logic?
Is the term "civilization" even defined in this context? Seems to refer to citizenship, and alien life might not even know of the concept of individuality. But let's say space traveling life (life also is a bit diffuse of a concept, might be technology created by life). And we are ourselves the only known example of that, very narcissistic, but that's what we have. Knowing human kind, our civilization, had we been a billion years older, we would be everywhere in this galaxy. And make one helluva of a show that we as ducklings today would've noticed. We would've gone to Earth-like planets and like besserwissers told whatever inhabitants there how to do their gardening, taking care of the environment, as our God ghost told us in Genesis.

But the sky is pitch black and deader than a rock. If Ouma were an artificial space probe, like our flyby probe at Pluto, then their Alan Stern wouldn't have held a happy press conference about it. Quite a better trajectory could easily have been chosen.
And not to digress too much, but all life on Earth is related. Since four billion years or so. It is as if lightning struck once, and from there on. More than 15 orbits around the Milky Way later, and it never happened again. I lean towards us being unique. That's not to say that other unique stuff doesn't exist out there. Heck, if we are, then anything is possible! But that our experience gives very little clue as to what that might be.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: ThereIWas3 on 11/09/2018 03:26 PM
We very nearly missed this one.  There is no way to know how many previous encounters there were, especially if they did not plunge so deep into the solar system.   Even ones like this would have been undetectable more than a few decades ago with available telescope technology.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Comga on 11/09/2018 03:40 PM
The variable brightness on this object is believed to be due to a tumbling motion and a high aspect ratio.

With ordinary comets which have the visible tail, do any of them exhibit any tumbling motion?

Could it be that Oumuamua's tumbling is the reason why it doesn't have a visible tail?

I think all observed comet nuclei rotate to some degree, and some comets display rotating features in their comas.
Tumbling does not prevent the formation of a tail on a comet.

PS. Can we move the ‘aliens’ and philosophy of science discussion to its own thread?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: sanman on 11/11/2018 01:22 AM
Is it possible that Oumuamua is a flat oval-shape?

https://www.skyandtelescope.com/astronomy-news/could-oumuamua-be-an-interstellar-pancake/

(https://s22380.pcdn.co/wp-content/uploads/Oumuamua-painting-Hartmann-480p.jpg)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Bynaus on 11/11/2018 11:19 AM
Is it possible that Oumuamua is a flat oval-shape?

https://www.skyandtelescope.com/astronomy-news/could-oumuamua-be-an-interstellar-pancake/

(https://s22380.pcdn.co/wp-content/uploads/Oumuamua-painting-Hartmann-480p.jpg)

Flying Saucer confirmed. ;)
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: plutogno on 11/11/2018 12:39 PM
Is it possible that Oumuamua is a flat oval-shape?

https://www.skyandtelescope.com/astronomy-news/could-oumuamua-be-an-interstellar-pancake/

(https://s22380.pcdn.co/wp-content/uploads/Oumuamua-painting-Hartmann-480p.jpg)

am I the only one who sees the Millennium Falcon in this image?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: mcgyver on 11/15/2018 07:33 AM
Speculation from a new scientific paper

That paper was quite detailed (3 pages of equations) and carefully explains why the other explanations do not hold together but that their "light sail" hyposthesis is a good fit.  But the acceleration they report is (4.92 ± 0.16) × 10 −4 cm s −2 which is 100x more than in an earlier comment here.  Still, that is an awfully small number, and I wonder how that was measured.
I did another calculation:
Oumuamua size: 230m x 25m x 25m = 281750 m3
Vesta density: 3400 kg/m3
Possible Oumuamua mass: 9.6E8 kg
Needed force for 4.92E-6 m/s2 acceleration:
F = 9.6E8 * 4.92E-6 = 4723 N

(around the force of Apollo 11 descent module)


ISS mass density, considering the whole volume it's included in (72m x 20m x 108m = 155520 m3) and 420000 kg mass is 2.7 kg/m3 (I don't know the actual volume and density).
For such a density, the needed force for Oumuamua would be 3.5 Newton.


ISS habitable volume is 1200 m3, so maybe its actual solid volume is around 5000 m3? In that case, its density would be 84 kg/m3. Let's assume a "possible volume range" of 3 to 100 kg/m3: this would lead, for Oumuamua acceleration, to a force range between 4 and 140 N.





Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: mcgyver on 11/15/2018 07:44 AM
Is anybody able to calculate how long it would take for one of those theoretical "laser propelled microprobes" to reach Oumuamua?
I can't understand how such probes can communicate with Earth, but if they can, this could be an interesting project.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/15/2018 08:42 PM
NASA Learns More About Interstellar Visitor 'Oumuamua (https://www.jpl.nasa.gov/news/news.php?feature=7280)

In November 2017, scientists pointed NASA's Spitzer Space Telescope toward the object known as 'Oumuamua - the first known interstellar object to visit our solar system. The infrared Spitzer was one of many telescopes pointed at 'Oumuamua in the weeks after its discovery that October.

'Oumuamua was too faint for Spitzer to detect when it looked more than two months after the object's closest aproach to Earth in early September. However, the "non-detection" puts a new limit on how large the strange object can be. The results are reported in a new study published today in the Astronomical Journal and coauthored by scientists at NASA's Jet Propulsion Laboratory in Pasadena, California.

The new size limit is consistent with the findings of a research paper published earlier this year, which suggested that outgassing was responsible for the slight changes in 'Oumuamua's speed and direction as it was tracked last year: The authors of that paper conclude the expelled gas acted like a small thruster gently pushing the object. That determination was dependent on 'Oumuamua being relatively smaller than typical solar system comets. (The conclusion that 'Oumuamua experienced outgassing suggested that it was composed of frozen gases, similar to a comet.)

"'Oumuamua has been full of surprises from day one, so we were eager to see what Spitzer might show," said David Trilling, lead author on the new study and a professor of astronomy at Northern Arizona University. "The fact that 'Oumuamua was too small for Spitzer to detect is actually a very valuable result."

'Oumuamua was first detected by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala, Hawaii (the object's name is a Hawaiian word meaning "visitor from afar arriving first"), in October 2017 while the telescope was surveying for near-Earth asteroids.

Subsequent detailed observations conducted by multiple ground-based telescopes and NASA's Hubble Space Telescope detected the sunlight reflected off 'Oumuamua's surface. Large variations in the object's brightness suggested that 'Oumuamua is highly elongated and probably less than half a mile (2,600 feet, or 800 meters) in its longest dimension.

But Spitzer tracks asteroids and comets using the infrared energy, or heat, that they radiate, which can provide more specific information about an object's size than optical observations of reflected sunlight alone would.

The fact that 'Oumuamua was too faint for Spitzer to detect sets a limit on the object's total surface area. However, since the non-detection can't be used to infer shape, the size limits are presented as what 'Oumuamua's diameter would be if it were spherical. Using three separate models that make slightly different assumptions about the object's composition, Spitzer's non-detection limited 'Oumuamua's "spherical diameter" to 1,440 feet (440 meters), 460 feet (140 meters) or perhaps as little as 320 feet (100 meters). The wide range of results stems from the assumptions about 'Oumuamua's composition, which influences how visible (or faint) it would appear to Spitzer were it a particular size.

Small but Reflective

The new study also suggests that 'Oumuamua may be up to 10 times more reflective than the comets that reside in our solar system - a surprising result, according to the paper's authors. Because infrared light is largely heat radiation produced by "warm" objects, it can be used to determine the temperature of a comet or asteroid; in turn, this can be used to determine the reflectivity of the object's surface - what scientists call albedo. Just as a dark T-shirt in sunlight heats up more quickly than a light one, an object with low reflectivity retains more heat than an object with high reflectivity. So a lower temperature means a higher albedo.

A comet's albedo can change throughout its lifetime. When it passes close to the Sun, a comet's ice warms and turns directly into a gas, sweeping dust and dirt off the comet's surface and revealing more reflective ice.

'Oumuamua had been traveling through interstellar space for millions of years, far from any star that could refresh its surface. But it may have had its surface refreshed through such "outgassing" when it made an extremely close approach to our Sun, a little more than five weeks before it was discovered. In addition to sweeping away dust and dirt, some of the released gas may have covered the surface of 'Oumuamua with a reflective coat of ice and snow - a phenomenon that's also been observed in comets in our solar system.

'Oumuamua is on its way out of our solar system - almost as far from the Sun as Saturn's orbit - and is well beyond the reach of any existing telescopes.

"Usually, if we get a measurement from a comet that's kind of weird, we go back and measure it again until we understand what we're seeing," said Davide Farnocchia, of the Center for Near Earth Object Studies (CNEOS) at JPL and a coauthor on both papers. "But this one is gone forever; we probably know as much about it as we're ever going to know."

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit:

https://spitzer.caltech.edu

https://www.nasa.gov/spitzer

Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: RotoSequence on 11/15/2018 09:45 PM
Does it bother anyone else that the outgassing hypothesis is treated as such an open and shut thing in this press release, given the inconsistencies in Oumuamua's solar encounter dynamics when compared to cometary behavior?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Star One on 11/15/2018 10:23 PM
Does it bother anyone else that the outgassing hypothesis is treated as such an open and shut thing in this press release, given the inconsistencies in Oumuamua's solar encounter dynamics when compared to cometary behavior?

Yes I agree.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: mcgyver on 11/16/2018 10:18 AM
Does it bother anyone else that the outgassing hypothesis is treated as such an open and shut thing in this press release, given the inconsistencies in Oumuamua's solar encounter dynamics when compared to cometary behavior?
sudden, short and unique explosion/sublimation of an underground ice block due to solar heating?
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Zed_Noir on 11/16/2018 11:31 AM
Does it bother anyone else that the outgassing hypothesis is treated as such an open and shut thing in this press release, given the inconsistencies in Oumuamua's solar encounter dynamics when compared to cometary behavior?
sudden, short and unique explosion/sublimation of an underground ice block due to solar heating?

That should be at the closest approach to the sun. If there is any water that is not sublime away during inbound approach.

But I am not aware of any reports of significant out gassing of either volatiles or dust.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: mcgyver on 11/16/2018 12:11 PM

But I am not aware of any reports of significant out gassing of either volatiles or dust.
That's why I assumed "sudden and short", like a bubble exploding.
Anyway, without further data, it could have been anything.
Could it even be an error in measuring or calculating? 0.00000492 meter/s2  on a body 800 meters long and some billions meters away.
Or is the datum confirmed?



Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: Bynaus on 11/16/2018 12:51 PM
A sudden blow would have affected the orbit in a different way - what was observed was a constant shift, as if a force, roughly proportional to the inverse of the distance to the Sun squared, was acting on the object. So no, a sudden blow can't explain the orbit.

Its quite remarkable that even if we assume that the CO, CO2, dust emissions are at their upper limit (by no way a given), this would require the water to CO, CO2 ratio in the comet to be much higher than in solar system comets (if water evaporating is the reason for the push). Sure, you can construct a scenario where CO, CO2 evaporates first, so that water evaporates on the outgoing leg of the hyperbolic orbit, but it just sounds so... constructed. We really don't understand this object.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: MoonMoon on 11/16/2018 08:19 PM
Would it be possible for ETI beings to design a craft that appears to be tumbling and outgassing? Better yet why not design a probe that is meant to be studied or captured? Why not send your tech out there like we have with gold records and dvds? I’m not a believer in the whole “we are being visited on purpose” but I do believe a probe with AI can exist out there. This conversation needs to be welcomed amongst us average folks and scientific community.
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: John-H on 11/16/2018 10:34 PM
This is the first object we have seen that has not been touched by any sunlight for a long, long time. Do we have any measurement of how big, or how heavy, it is except for the amount of light reflected? Could it be much smaller and shinier, or much less dense than a normal asteroid, and could it thus be much more affected by radiation pressure?  Perhaps it is a very light collection of hoar frost particles.

John
Title: Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
Post by: hop on 11/17/2018 02:49 AM
This is the first object we have seen that has not been touched by any sunlight for a long, long time.
Oort cloud comets can have periods in the millions of years range, and many likely spend far longer beyond at tens of thousands of AU before they get nudged into the planetary region. That kind of distances shouldn't be terribly different from the larger interstellar environment.

Quote
Do we have any measurement of how big, or how heavy, it is except for the amount of light reflected? Could it be much smaller and shinier, or much less dense than a normal asteroid, and could it thus be much more affected by radiation pressure? 
Not really. The size, density and albedo are very much open questions. Papers have argued that various observations point toward various values, but there are generally a lot of unverifiable assumptions involved.