Interstellar Interlopers, Coming in from the great beyond Options

[hendric]

With all the hot Jupiters we've discovered, I would expect that this object is more likely from the inner portion of its source solar system, scattered to a Galactic orbit by an approaching Big Brother.

Maybe it's not a stripped extrasolar Oort Cloud member, but rather an extrasolar Vulcanoid!

That would explain the lack of outgassing during the close approach, it's already been "cooked dry". Don't know enough about asteroid spectrography to talk about if it could be as red as it is with limited organics. Maybe Alan Stern can comment?

[Hungry4info]

With as deep in their star's gravitational wells as they are, it would be quite a feat for a hot Jupiter to kick an asteroid out of its planetary system that wasn't already on a highly eccentric orbit.

[HSchirmer]

With as deep in their star's gravitational wells as they are, it would be quite a feat for a hot Jupiter to kick an asteroid out of its planetary system that wasn't already on a highly eccentric orbit.

Well, I think the idea is a Nice model, gas giant forms at the snowline, then makes it's way to the inner orbit by gas drag,
or by dumping excess angular momentum by scattering asteroids or comets.

It's counter-intuitive, gas giants don't have retro-rockets to slow them down and spiral in, so their method of braking is tossing asteroids around.
-edit- It's sort of a solar system version of the gravel run-outs you have for trucks that loose their brakes - tossing small rocks around is a way to scrub off speed.

[hendric]

Well, my assumption was that the source solar system had a lighter mass sun, such as a red dwarf. Should be much easier for a hot jupiter in that situation to knock about protoplanetoids during its dive from the outer parts to the inner parts. Considering how compact some of these systems are, multiple encounters of the same or other Jupiter class planets in the same system is entirely likely.

[JRehling]

Hot Jupiters are relatively rare. We discovered so many of them early in the exoplanet discovery process because there are two observational biases favoring them: size and proximity to their star, both factors favored by both the Doppler method and the transiting method. There are only about 0.06 Jupiter-sized planets per sunlike star with periods <500 days, and even fewer in the "hot" bin.

The most common kind of star, red dwarfs, have few Jupiter-sized planets at all, so far as we know. Sunlike stars are less common, but have more Jupiter-sized planets. Still larger stars are still rarer, but may have more, if the trend continues.

We're almost totally ignorant about the frequency of planets distant (>10 AU) from stars. We know that they exist (Fomalhaut b, Uranus, Neptune) but not their frequency.

All told, we can't possibly have a good handle on the various observational biases: How many stars of what size have planets of what size at what distances, and potential interloper population at what distances, and at what times in the evolutionary history of the system. We only have very partial information to begin to answer this. The dynamics follow universal laws that are well understand, but most of the rest is unconstrained now. We know the planet population function only for the more common kinds of star and only for relatively close-in orbits (~500 days for Earths and Super-Earths, out to ~10 AU for giant planets). And then there are biases allowing the body's survival and having made the long journey here. Unknowns on top of unknowns.

It does seem likely that this body is "baked" / rocky and not comet-like. Empirical observations FTW!

[fredk]

Here's a twist - a paper looking at the possibility that the interloper is a chunk of dark matter: Could 1I/'Oumuamua be macroscopic dark matter?

There are two mass ranges for such lumps allowed by gravitational lensing and cosmic microwave background constraints. The paper is pretty sketchy, but it seems that the lower mass range (around 10^15 g) would imply that many more of these should've been seen, so that range should be ruled out. The heavier mass range (around 10^22 g) is potentially ruled out by the fact that such a heavy mass would produce noticable perturbations on the orbits of solar system bodies. (The heavy range corresponds very roughly to masses in the range of a small moon such as Pandora to a mid-sized moon such as Iapetus.)

So the idea may not work, which might be interesting as a new constraint on certain types of dark matter.

[nprev]

Well...at least it's a testable hypothesis if they claim it would have caused perturbations of the inner system during its passage. Short of that, you could use Occam's Sledgehammer to eliminate it...no need for fine work provided by the Razor...

[dudley]

Examination of the light curve of Oumuamua as it rotates is now reported to suggest an object 30 meters wide by 180 long. That's a remarkably long, thin object, about the shape of a thick cigar; length to width ratio 6 to 1. That's over twice the longest, thinest asteroid known to inhabit our solar system.

[TheAnt]

Examination of the light curve of Oumuamua as it rotates is now reported to suggest an object 30 meters wide by 180 long. That's a remarkably long, thin object.....

It might also be a darker area that seemingly gives that result.
If that is correct it might be a shard from some kind of collision, or perhaps even from uneven heating when it passed close to its primary star when it got ejected.

@nprev: "Occam's Sledgehammer" Yes I felt that paper was bordering on too speculative. That the first interstellar object also have to be something really spectacular.
Then again, it's good science to check even on less likely possibilities.

[Explorer1]

Examination of the light curve of Oumuamua as it rotates is now reported to suggest an object 30 meters wide by 180 long. That's a remarkably long, thin object, about the shape of a thick cigar; length to width ratio 6 to 1. That's over twice the longest, thinest asteroid known to inhabit our solar system.

Very interesting/strange...How can something like that stay together? It's not a rubble pile like Itokawa (which is bigger), so it must be more solid?

I wonder what Arthur C. Clarke would say...

[fredk]

It's not entirely clear what Occam would say about this. We know dark matter exists, but have no idea what form it takes. There's been no sign of the "nominal" WIMPS yet, so "chunks" are a real possibility (medium-sized black holes are currently popular, which, being black, we wouldn't've seen).

Another point against the dark matter hypothesis I forgot to mention is that Oumuamua was moving about a tenth the speed expected for typical dark matter particles, but apparently at a not-surprising speed for an interstellar interloper.

The other side of this is: what do we expect for the local density/distribution of asteroids/comets kicked out of extrasolar systems? Surely there must be some estimates of this. Of course any such estimates would span a wide range since the details are very unclear, but if the estimates are that we'd expect to see such an interloper no more often than once in, say, 10 000 years, then the observation of one would be an important data point and perhaps point to other possibilities (if not a gross misunderstanding of solar systems). On the other hand, a predicted rate consistent with one per decade or so would support such an origin. Has anyone seen such estimates?

[dudley]

Very interesting/strange...How can something like that stay together? It's not a rubble pile like Itokawa (which is bigger), so it must be more solid?

I wonder what Arthur C. Clarke would say...

The spectra of the object suggested similarities to D and P class asteroids. These are made of silicates, carbon, and perhaps some ice in their interiors. I don't know how well such material would bear spinning, once every 8 hours, if formed into such a long thin shape. Seeing no asteroids belonging to our own solar system that come anywhere near this shape, I'm inclined to suspect that such an object would be likely to fly apart, or be knocked apart by impacts.

[Ron Hobbs]

ESO has a press release out today with an artist's impression of 'Oumuamua. It looks very much like the proverbial needle in a haystack.



https://www.eso.org/public/news/eso1737/

I bet Arthur Clarke would have fun seeing this discovery.

[Gerald]

Possibly a collision fragment. But figures of equilibrium of gravitationally bound polytropes allow for elongated Jacobi ellipsoids, too.

[dudley]

The differences in reflectivity, through the course of its rotation, are held to imply that the object is at least 10 times longer than it is wide. If the two ends don't align directly with Earth, which would be quite a coincidence, the elongation would be even greater, we're told. The 'fat cigar' has become quite a thin one! Not a contact binary, it seems. The object is reported to be spinning too rapidly for this to be a stable configuration. The article, linked below, has some even less probable explanations for the object.

BBC Article