Author Topic: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)  (Read 60256 times)

Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #80 on: 11/02/2017 01:11 AM »
Pole, Pericenter, and Nodes of the Interstellar Minor Body A/2017 U1

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.


Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #81 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) 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.

Offline Ben the Space Brit

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #82 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!
« Last Edit: 11/02/2017 02:15 PM by Ben the Space Brit »
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Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #83 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) 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!

Online nacnud

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #84 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.
« Last Edit: 11/02/2017 03:36 PM by nacnud »

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #85 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")
« Last Edit: 11/02/2017 08:35 PM by hop »

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #86 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.

Offline sanman

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #87 on: 11/03/2017 02:02 AM »
How much damage would it have done if it hit the Earth?

Offline Ben the Space Brit

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #88 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.
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Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #89 on: 11/07/2017 01:29 AM »
Origin of Interstellar Object A/2017 U1 in a Nearby Young Stellar Association?

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

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

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.
« Last Edit: 11/07/2017 01:33 AM by Mongo62 »

Offline jebbo

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #90 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

--- Tony
« Last Edit: 11/07/2017 04:53 PM by jebbo »

Offline Ben the Space Brit

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #91 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?
"Oops! I left the silly thing in reverse!" - Duck Dodgers

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Offline jebbo

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #92 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

Offline missinglink

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #93 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?

Online ugordan

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #94 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.
« Last Edit: 11/07/2017 08:01 AM by ugordan »

Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #95 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.

Online ugordan

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #96 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.

Offline ChrisWilson68

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #97 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.

Offline Bynaus

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #98 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.

Offline Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper?
« Reply #99 on: 11/08/2017 12:58 AM »
On the Consequences of the Detection of an Interstellar Asteroid

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

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.
« Last Edit: 11/08/2017 01:00 AM by Mongo62 »

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