Interstellar Asteroid 1I/2017 U1 'Oumuamua

[bystander]

Small Asteroid or Comet 'Visits' from Beyond the Solar System
Institute for Astronomy | University of Hawaii | 2017 Oct 26

Interstellar Visitor's Path Through The Solar System Credit: Brooks Bays / SOEST Publication Services / UH IfA

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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. ...

Small Asteroid or Comet "Visits" from Beyond the Solar System
NASA | JPL-Caltech | 2017 Oct 26

[neufer]

[b][color=#0000FF][size=150]Lyre, lyre, pants on fyre.[/size][/color][/b]

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<<A/2017 U1 (Previously C/2017 U1 (PANSTARRS)) is an extremely hyperbolic object discovered on October 18, 2017 by the Pan-STARRS telescope when the object was 0.2 AU from Earth. With an eccentricity of 1.18-1.19, it has the highest eccentricity of any known object in the solar system. With an eccentricity of 1.057, C/1980 E1 was the previous record holder.

It is the first possible example of an interstellar object, appearing to originate from the constellation Lyra, with an hyperbolic excess velocity of 26 km/s. JPL solution #1 indicates that one hundred years ago, the object was roughly 544 AU from the Sun. Assuming it is a rock with an albedo of 10%, it would be roughly 160 meters in diameter. The asteroid is calculated to have gone through perihelion [of 0.253 AU at ~88 km/s] on 9 September 2017 and passed about 0.16 AU from Earth on 14 October 2017. The object is small and faint, and has already faded to apparent magnitude 21.

On October 25, in very deep stacked images taken at the Very Large Telescope (VLT) the object was found to show no presence whatsoever of any cometary nature. The object was renamed A/2017 U1, becoming the first comet to ever be re-designated as an asteroid. Its asteroidal nature indicates that it must have formed within the frost line of whatever stellar system it originated from, or have been in the inner solar system long enough for all ice to sublimate.>>

[MarkBour]

Rendezvous With Rama, Arthur C. Clarke:

And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes.

So, perhaps we should keep an eye on this general trajectory?

[neufer]

Rendezvous With Rama, Arthur C. Clarke:

And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes.

So, perhaps we should keep an eye on this general trajectory?

Sticks and stones may break my bones...
but if you want to do a really good job try tossing 160 meter asteroids.

[daddyo]

It's seems hard to believe interstellar asteroids are this rare. Maybe there are waves of them that come in from old exploded stars.

[BDanielMayfield]

Well, (it came from) far out

It's seems hard to believe interstellar asteroids are this rare. Maybe there are waves of them that come in from old exploded stars.

Their rarity is due to the very large average separation between star systems in these parts. It will be really cool if they can figure out which system it likely came from.

Bruce

[BDanielMayfield]

Rendezvous With Rama, Arthur C. Clarke:

And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes.

So, perhaps we should keep an eye on this general trajectory?

It “used” the Sun’s gravity well to make what looks like a more than 90 degree “course adjustment.” Hey, did we just get “probed”?

Bruce

[neufer]

Well, (it came from) far out

It seems hard to believe interstellar asteroids are this rare. Maybe there are waves of them that come in from old exploded stars.

Their rarity is due to the very large average separation between star systems in these parts.
It will be really cool if they can figure out which system it likely came from.

Hence: It seems rather hard to believe interstellar asteroids are this common
(Note that this dry asteroid had to come within about 0.25 AU of Earth for us to
detect it whereas we can often detect icy interstellar comets tens of AU away.)

I'm beginning to envision all the planetary nebula we currently observe as
primarily A-F stars that have recently lost over half their mass so as to
release all their planets, dry asteroids & icy bodies into interstellar space.

[BDanielMayfield]

Well, (it came from) far out

It seems hard to believe interstellar asteroids are this rare. Maybe there are waves of them that come in from old exploded stars.

Their rarity is due to the very large average separation between star systems in these parts.
It will be really cool if they can figure out which system it likely came from.

Hence: It seems rather hard to believe interstellar asteroids are this common
(Note that this dry asteroid had to come within about 0.25 AU of Earth for us to
detect it whereas we can often detect icy interstellar comets tens of AU away.)

Good point. Even the Pan-STARS survey could have very easily missed it due to weather, etc. It looks like they barely managed to catch it as it was already on its way out and dimming rapidly.

I'm beginning to envision all the planetary nebula we currently observe as
primarily A-F stars that have recently lost over half their mass so as to
release all their planets, dry asteroids & icy bodies into interstellar space.

Even better point. But only distant orbiters, close-in bodies would likely get destroyed in the red giant phase. That could have been what dried it out. Retracing its path back to its origin might show the point where a white dwarf used to be. But it would have taken an extremely long time to have made the interstellar crossing. Its parent star might be half way across the Milky Way by now, right?

Bruce

[MarkBour]

[
Sticks and stones may break my bones...
but if you want to do a really good job try tossing 160 meter asteroids.

Ouch! Hopefully, it wasn't the first and smallest of a group.

It “used” the Sun’s gravity well to make what looks like a more than 90 degree “course adjustment.” Hey, did we just get “probed”?
Bruce

I'm guessing that no sky survey we have undertaken, begun, or even conceived of is going to help give us much advance warning for one of these. So I hope they are very, very rare.

[neufer]

I'm beginning to envision all the planetary nebula we currently observe as
primarily A-F stars that have recently lost over half their mass so as to
release all their planets, dry asteroids & icy bodies into interstellar space.

Even better point. But only distant orbiters, close-in bodies would likely get destroyed in the red giant phase. That could have been what dried it out. Retracing its path back to its origin might show the point where a white dwarf used to be. But it would have taken an extremely long time to have made the interstellar crossing. Its parent star might be half way across the Milky Way by now, right?

A/2017 U1 may well have been in orbit around the Milky Way for over a billion years before its close encounter with our Solar System.
(At a speed 0.009% the speed of light vs-a-vi the Sun a billion years would place it on the other side of the Milky Way.)

[BDanielMayfield]

I'm beginning to envision all the planetary nebula we currently observe as
primarily A-F stars that have recently lost over half their mass so as to
release all their planets, dry asteroids & icy bodies into interstellar space.

Even better point. But only distant orbiters, close-in bodies would likely get destroyed in the red giant phase. That could have been what dried it out. Retracing its path back to its origin might show the point where a white dwarf used to be. But it would have taken an extremely long time to have made the interstellar crossing. Its parent star might be half way across the Milky Way by now, right?

A/2017 U1 may well have been in orbit around the Milky Way for over a billion years before its close encounter with our Solar System.
(At a speed 0.009% the speed of light vs-a-vi the Sun a billion years would place it on the other side of the Milky Way.)

So, it could have come from a great number of potential systems, depending upon how long it has been since it was ejected from the system it formed in. I recon that, just as stars hardly ever have such close encounters, individual ejected objects hardly ever do as well, it’s just that such interstellar objects must vastly outnumber stars so we finally caught one passing through.

Bruce

[daddyo]

Probably all those gravitational vacuum cleaners have swept up most of the interstellar grit.

It might be interesting to directly see what the rest of the universe is made of by landing on one. Might be a real mess if it turned out to be antimatter...

[HiYoSilver]

What if the visitor is not a visitor, but was once part of the solar system, was flung out, and is just re-entering?

[HiYoSIlver]

Anyway .. the thought of being ejected brings back memories of high school math classes.

[Chris Peterson]

What if the visitor is not a visitor, but was once part of the solar system, was flung out, and is just re-entering?

If it had been flung out but remained in a closed orbit (so that it could reenter), we'd see an eccentricity of slightly less than one, not significantly more than one (1.19). This is almost certainly a first time visitor that originated elsewhere.

[neufer]

What if the visitor is not a visitor, but was once part of the solar system, was flung out, and is just re-entering?

If it had been flung out but remained in a closed orbit (so that it could reenter), we'd see an eccentricity of slightly less than one, not significantly more than one (1.19). This is almost certainly a first time visitor that originated elsewhere.

Have astronomers discovered our first interstellar visitor?
by Phil Plait

<<If there’s another planet in our solar system orbiting far, far beyond Neptune, and the asteroid started somewhere nearby (that is, as part of our solar system since the start) and passed close to this planet, it could get a kick in velocity and get flung down towards us at higher speed. However, a lot of things have to line up for this to happen so the odds on this are incredibly low, so low I’d put them at essentially 0. But I’d be remiss not to at least mention it.>>

[neufer]

A/2017 U1 may well have been in orbit around the Milky Way for over a billion years before its close encounter with our Solar System. (At a speed 0.009% the speed of light vs-a-vi the Sun a billion years would place it on the other side of the Milky Way.)

So, it could have come from a great number of potential systems, depending upon how long it has been since it was ejected from the system it formed in. I recon that, just as stars hardly ever have such close encounters, individual ejected objects hardly ever do as well, it’s just that such interstellar objects must vastly outnumber stars so we finally caught one passing through.

Indeed they must.

Another method contributing to the interstellar asteroid population is:

Have astronomers discovered our first interstellar visitor?
Phil Plait

<<For quite some time now astronomers have understood that early in the life of the solar system, the big planets have moved around. Jupiter and Saturn were farther out from the Sun and migrated inwards. This can disrupt the orbits of smaller objects like comets and asteroids, flinging them about hither and yon. Eventually this cleared a lot of debris from the young solar system, dropping these rocks into the Sun or ejecting them out into interstellar space.>>

[BDanielMayfield]

A/2017 U1 may well have been in orbit around the Milky Way for over a billion years before its close encounter with our Solar System. (At a speed 0.009% the speed of light vs-a-vi the Sun a billion years would place it on the other side of the Milky Way.)

So, it could have come from a great number of potential systems, depending upon how long it has been since it was ejected from the system it formed in. I recon that, just as stars hardly ever have such close encounters, individual ejected objects hardly ever do as well, it’s just that such interstellar objects must vastly outnumber stars so we finally caught one passing through.

Indeed they must.

Another method contributing to the interstellar asteroid population is:

Have astronomers discovered our first interstellar visitor?
Phil Plait

<<For quite some time now astronomers have understood that early in the life of the solar system, the big planets have moved around. Jupiter and Saturn were farther out from the Sun and migrated inwards. This can disrupt the orbits of smaller objects like comets and asteroids, flinging them about hither and yon. Eventually this cleared a lot of debris from the young solar system, dropping these rocks into the Sun or ejecting them out into interstellar space.>>

Yes. I would think that the early ejection population would be greater than the numbers of those released by stellar end phase events, but maybe not. The fact that A/2017 U1 was dry suggests that it either never had any volatiles or that they had been cooked off somehow. Its speed also suggests an energetic expulsion rather than a gentle release.

Bruce

[Chris Peterson]

Its speed also suggests an energetic expulsion rather than a gentle release.

Actually, its speed is low for an interstellar object. But that tells us nothing about the speed of its ejection, only about the relative speed of its parent system with respect to our own.

[BDanielMayfield]

Its speed also suggests an energetic expulsion rather than a gentle release.

Actually, its speed is low for an interstellar object. But that tells us nothing about the speed of its ejection, only about the relative speed of its parent system with respect to our own.

Interesting Chris. What speeds should be expected for such rare objects?

[Chris Peterson]

Its speed also suggests an energetic expulsion rather than a gentle release.

Actually, its speed is low for an interstellar object. But that tells us nothing about the speed of its ejection, only about the relative speed of its parent system with respect to our own.

Interesting Chris. What speeds should be expected for such rare objects?

It depends on where it came from. The fact that this one was traveling only a little above our system's escape velocity suggests a nearby star which is traveling in a similar orbit to our own. Most of the stars in the galaxy have a greater relative speed with respect to us, and therefore anything escaping from them would pass through our system faster (assuming no other major perturbations along the way).

[neufer]

Its speed also suggests an energetic expulsion rather than a gentle release.

Actually, its speed is low for an interstellar object. But that tells us nothing about the speed of its ejection, only about the relative speed of its parent system with respect to our own.

Which begs the question of why we didn't first observe interstellar asteroid/comets coming in at two to three times that speed since their interception rate should be some two to three times higher (and their rapid motion might have been more pronounced).

[Doum]

At first i tought it was possible for it to have been in the Oort cloud and it encounter planet nine wich make it come toward us with a little above our system's escape velocity. But since it was dryed i suppose its not possible. just a tought.

[Chris Peterson]

Its speed also suggests an energetic expulsion rather than a gentle release.

Actually, its speed is low for an interstellar object. But that tells us nothing about the speed of its ejection, only about the relative speed of its parent system with respect to our own.

Which begs the question of why we didn't first observe interstellar asteroid/comets coming in at two to three times that speed since their interception rate should be some two to three times higher (and their rapid motion might have been more pronounced).

There are many questions around the apparent rate we'd expect for interstellar bodies, given current models. (We've been looking for evidence of meteoroids in significantly hyperbolic orbits for the last ten or twenty years, as we've had the technology to determine that from a large number of recorded meteors. So far, nothing but a small number of possible, but unlikely observations.)