How `Oumuamua Got Its Shape

Computer models have come up with a possible explanation for the strange shape of ‘Oumuamua. The theory is that the object made a close pass to its home star. As it neared the star, the rocky material became malleable and tidal forces stretched it into its elongated shape.

This same effect caused the comet Comet Shoemaker–Levy 9 to break into a "string of pearls" as it entered deep into the gravitational well of Jupiter.

The process is akin to making a super-thin snake from a ball of Play-Doh. As the Play-Doh gets progressively thinner, smaller chunks start to shred off, with each of the bits still retaining their elongated shape.

gizmodo.com...

I think it’s the Yuuzhan Vong lol. That’s cool though. Weird things happen out there.

Either that or it was a Giant Interstellar Space Rat dropping.

a reply to: willzilla

That's sort of part of the problem of figuring out what the heck it is. Other studies have concluded that there must be a lot of those things out there so how could such an odd thing be relatively common? This provides an answer.

At the same time, it also provides an explanation for why the surface of the object is so "dry", and how getting close to the Sun could cause volatile materials (H2O) beneath the surface to be ejected and produce that famous non-gravitational acceleration.

It's a nice neat package.

But I have never said that `Oumuamua is not a spaceship.

So they’re fairly certain about its formation process, how about where it came from? Any ideas as to where and how far this interstellar interloper travelled?

And from the read they expect these types of interstellar interlopers to frequent the Milky Way — Panspermia getting some love.

a reply to: Cravens

Any ideas as to where and how far this interstellar interloper travelled?

Only in the vaguest of terms, finding stars it might have come from, or have influenced its path through space. The Sun is now another one of those pinball bumpers.

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.

arxiv.org...

There are other hypotheses as well. None likely to be definitive.

Very cool. It's fascinating how "big things" with "big force" mimic "small things" with "small force" (like the play-doh analogy).

I read a thing about microscopic alien life possibly riding on rocks like Oumuamua. It made me think about larger alien life forms using rocks like this to house equipment for prolonged space journeys. It was a cool thought. But here's some science based stuff to enjoy:

www.discovermagazine.com...

In a January 2019 study published in the International Journal of Astrobiology, Loeb and a Harvard undergraduate student Amir Siraj suggest that Earth-grazing comets and interstellar objects could have snagged microbes from high in our atmosphere and then carried them out into the Milky Way. Their estimates predict this could have already happened many times, depending on how high up life exists on our planet. "We found that there could be thousands, if not tens of thousands, that could pass through the Earth's atmosphere, collect microbes, and then get kicked to another solar system," Loeb says.

Basically, it depends on your definition of "space ship." If rock carrying some form of life counts, then I'll call it.

a reply to: Crosswinds

I have some problems with the notion that any living thing which originated from within an atmosphere could survive for hundreds of thousands, millions of years, in interstellar space.

But who knows.

a reply to: Phage

Nice, thanks for sharing! Its funy, I hadn't really given it thought until I read the thread title. What popped into my mind right away was melting close tona star, followed by cooling into its solid form as it hurtled away from the star. Not *quite* what they're saying, but not bad for a not-astrophysicist

I could imagine this could have resulted in some form of compression of material which squeezed out anything that would cause off-gassing and dust-particles, such that we end up with the seemingly inert object.

a reply to: Phage

I remember reading about how it was unusually reflective. Perhaps getting close to its sun caused a glazing on its surface resulting in its reflectivity...?

a reply to: MissSmartypants

I remember reading about how it was unusually reflective.

No. The opposite, actually. Pretty typical.

Reflectivity of the surface of ‘Oumuamua The surface reflectivity of ‘Oumuamua is consistent with D-type asteroids¹⁰ and comets.

www.researchgate.net...

a reply to: Phage

Gotcha. The pinball analogue paints a much clearer picture. Here’s to hoping Earth never becomes a bumper:

originally posted by: Phage
a reply to: MissSmartypants

I remember reading about how it was unusually reflective.

No. The opposite, actually. Pretty typical.

Reflectivity of the surface of ‘Oumuamua The surface reflectivity of ‘Oumuamua is consistent with D-type asteroids¹⁰ and comets.

www.researchgate.net...

l
According to NASA an article published in The Astronomical Journal stated that it may be 10 times more reflective than comets found in our solar system. According to the study, passing by our sun left it with a coating of ice.

a reply to: MissSmartypants

Passing the Sun gave it a coating of ice? That's interesting.
I don't suppose you have a link?

a reply to: Phage

I have a link to an article that mentions it's not quite icy at all.
www.theatlantic.com...
And I quote,

‘Oumuamua didn’t show signatures of ice or minerals found in rock, which means it’s neither icy nor rocky, at least not exactly. But it did show signs of carbon compounds. Fitzsimmons said previous studies have revealed that when carbon-rich, comet-like objects are exposed to the radiation that would be found in interstellar space, the material forms a crust that acts as insulation. If ‘Oumuamua has ice, as a comet would, it may be hiding beneath a mantle half a meter thick, formed after hundreds of millions—perhaps even billions—of years of bombardment by high-energy particles.

If there's any ice there, sounds like it's underneath the surface, not on top of it.

a reply to: Crosswinds

If there's any ice there, sounds like it's underneath the surface, not on top of it.

Yes, which fits well with this (non cometary) theory of its origin.

Also, I think, with the non-gravitational acceleration it exhibited as it said bye bye. Surface heating from sunlight would penetrate by convection to deeper areas where pockets of frozen volatile materials (ices) remain, heating them and causing them to burst forth. Providing a bit of propulsion.

originally posted by: Phage
a reply to: MissSmartypants

Passing the Sun gave it a coating of ice? That's interesting.
I don't suppose you have a link?

It's from an article on NASA.gov from Nov.14 2018 entitled "NASA Learns More About Interstellar Visitor Oumuanua".

I concede that the info may be out of date now.

a reply to: MissSmartypants
Thanks. Since you can't seem to post a link. Here it is
solarsystem.nasa.gov...

The NASA article oversimplifies the actual study that it's referring to. The study makes assumptions involving 3 different albedo models (the actual albedo is unknown because the actual size of the object is unknown). One of those models assumes that the object has a higher albedo than a comet and is therefore quite small. That seems to be the only model which the NASA article is referring to for some reason.

Since `Oumuamua was not discovered until it had rounded the Sun, there really is no way to know if its albedo increased as it did so. The study, using the assumption that the object is cometlike, makes the assumption that it behaved in a cometlike manner and shed dust from its surface as a result of outgassing (not that it gained a coating of ice).

Unfortunately, we do not have pre-perihelion observations to compare to these post-perihelion observations to test the hypothesis that 'Oumuamua brightened during its perihelion passage.

iopscience.iop.org...
This study, the topic of this thread, says "Nope, not a comet."


The study referenced in the NASA article, like the one I linked earlier (and others) show that there is probably nothing unusual about `Oumuamua in regard to albedo (reflectivity).

Just goes to show that consumer grade science often doesn't get it right when it tries to simplify things.

a reply to: Phage

Just as long its not one of these passing through ………

www.youtube.com...

a reply to: Phage

That is really interesting.

If it was rotating fast enough (end over end), it could have been pulled into a dumbbell shape.