Author Topic: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)  (Read 70935 times)

Offline sanman

  • Senior Member
  • *****
  • Posts: 4420
  • Liked: 668
  • Likes Given: 8
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #200 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?

Offline Mongo62

  • Full Member
  • ****
  • Posts: 963
  • Liked: 603
  • Likes Given: 135
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #201 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.

Online jebbo

  • Full Member
  • ****
  • Posts: 639
  • Cambridge, UK
  • Liked: 267
  • Likes Given: 245
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #202 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

Offline Star One

  • Senior Member
  • *****
  • Posts: 9707
  • UK
  • Liked: 1850
  • Likes Given: 183
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #203 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

Offline TakeOff

  • Full Member
  • ***
  • Posts: 395
  • Liked: 81
  • Likes Given: 109
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #204 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?
« Last Edit: 11/22/2017 05:47 PM by TakeOff »

Offline nacnud

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2361
  • Liked: 551
  • Likes Given: 229
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #205 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.


Offline Star One

  • Senior Member
  • *****
  • Posts: 9707
  • UK
  • Liked: 1850
  • Likes Given: 183
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #206 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/
« Last Edit: 11/22/2017 07:20 PM by Star One »

Online KelvinZero

  • Senior Member
  • *****
  • Posts: 3794
  • Liked: 597
  • Likes Given: 156
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #207 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

Offline hop

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 472
  • Likes Given: 826
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #208 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.

Online KelvinZero

  • Senior Member
  • *****
  • Posts: 3794
  • Liked: 597
  • Likes Given: 156
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #209 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.


Offline sanman

  • Senior Member
  • *****
  • Posts: 4420
  • Liked: 668
  • Likes Given: 8
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #210 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?

Offline hop

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 472
  • Likes Given: 826
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #211 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 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 ;)

Online ChrisWilson68

  • Senior Member
  • *****
  • Posts: 3786
  • Sunnyvale, CA
  • Liked: 2406
  • Likes Given: 3116
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #212 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.

Online KelvinZero

  • Senior Member
  • *****
  • Posts: 3794
  • Liked: 597
  • Likes Given: 156
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #213 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.

Offline Star One

  • Senior Member
  • *****
  • Posts: 9707
  • UK
  • Liked: 1850
  • Likes Given: 183
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #214 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 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.

Offline hop

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 472
  • Likes Given: 826
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #215 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 ;)

Online jebbo

  • Full Member
  • ****
  • Posts: 639
  • Cambridge, UK
  • Liked: 267
  • Likes Given: 245
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #216 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

Offline Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 7140
  • A spaceflight fan
  • London, UK
  • Liked: 662
  • Likes Given: 771
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #217 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.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Online Johnnyhinbos

  • Full Member
  • ****
  • Posts: 1380
  • Boston, MA
  • Liked: 1606
  • Likes Given: 222
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #218 on: 11/23/2017 11:16 AM »
So what gravity is generated at the poles of the object given its length and spin rate?
John Hanzl. Author, action / adventure www.johnhanzl.com

Offline nacnud

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2361
  • Liked: 551
  • Likes Given: 229
Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #219 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

Tags: