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Oumuamua’s oddball spin could be related to its origins as well. According to new research posted on the preprint server arXiv.org, the visitor is tumbling willy-nilly rather than smoothly rotating on its axis. The researchers, who declined to comment due to embargo concerns, state in their paper “1I/‘Oumuamua was likely set tumbling within its parent planetary system, and will remain tumbling well after it has left ours.” ‘Oumuamua’s motion, they speculate, could be due to a long-ago collision with another body or the extreme tidal torqueing it may have experienced during its ejection from its parent planetary system. Alternatively, its spin could come from the jetlike outgassing of icy material vaporizing in sunlight—the process that creates a cometary tail.
But, again, the object did not appear to sprout a tail when it closely approached our sun. If indeed ‘Oumuamua is an icy body, how did it avoid growing a cometary tail? David Jewitt, an astronomer at the University of California, Los Angles, suspects any ice might be buried under a layer of material damaged by the charged particles known as cosmic rays that bombarded ‘Oumuamua while it traveled through space. “The prolonged exposure will toast the surface,” forming a protective crust, he says.
Bailer-Jones and his colleagues found four stars that are possible candidates for 'Oumuamua's home world. All four of them are dwarf stars. The one that came closest to 'Oumuamua, at least about one million year ago, is the reddish dwarf star HIP 3757. It approached within about 1.96 light-years. Given the uncertainties unaccounted for in this reconstruction, that is close enough for 'Oumuamua to have originated from its planetary system (if the star has one). However, the comparatively large relative speed (around 25 km/s) makes it less probable for this to be 'Oumuamua's home.
The next candidate, HD 292249, is similar to our Sun, was a little bit less close to the object's trajectory 3.8 million years ago, but with a smaller relative speed of 10 km/s. The two additional candidates met 'Oumuamua 1.1 and 6.3 million years ago, respectively, at intermediate speeds and distances. These stars have been previously catalogued by other surveys, but little is known about them.
Instead, there was some additional acceleration when the object was close to the Sun. The likely explanation is that 'Oumuamua has some similarity to a comet – with ice that, when sufficiently heated by sunlight, produces gas that will in turn accelerate the source object like an exceedingly weak rocket engine.
However, given the highly elongated shape of the object, its torque asymmetry is likely higher, implying even faster evolution. This would have resulted in rapid rotational fission of 'Oumuamua during its journey through the Solar System and is clearly incompatible with the relative stability of its rotational state inferred from photometric variability. Based on these arguments, as well as the lack of direct signs of outgassing, we conclude that the classification of 'Oumuamua as a comet (invoked to explain its claimed anomalous acceleration) is questionable.
A few months later, another collaboration found that ’Oumuamua wasn’t just being pulled by the sun’s gravity. Instead, it was being slightly accelerated by an unseen force, which they argued could only be attributed to comet “outgassing” acting like a thruster. With this additional information, the case appeared to be closed. “Interstellar asteroid is really a comet,” read the headline of a press release put out by the European Space Agency.
The explanation seemed to fit with what we know about our own solar system. In the distant reaches beyond Neptune, countless comets orbit our sun. Anytime one of these comets gets too close to a planet, it could be ejected out into the galaxy. In contrast, there are far fewer asteroids in the asteroid belt, and they orbit closer to the sun, where they’re harder to knock into interstellar space. “There are more comets, and it’s easier to fling them away from a planetary system,” said Ann-Marie Madigan, an astrophysicist at the University of Colorado, Boulder. “For the first interstellar traveler that we see in our solar system, for that to be an asteroid, would be shocking.”
[Roman Rafikov] proposed such a scenario earlier this year, whereby an ordinary star dies, forming a white dwarf, and in the process rips apart a planet and launches the shards clear across the galaxy. ’Oumuamua is one of those shards. “Basically, it’s a messenger from a dead star,” he said.
[... M]ost of the past research into panspermia has focused on whether life could had been distributed through the solar system or neighboring stars. More specifically, these studies addressed the possibility that life could have been transferred between Mars and Earth (or other Solar bodies) via asteroids or meteorites. For the sake of their study, Ginsburg and his colleagues cast a wider net, looking at the Milky Way Galaxy and beyond.
As Dr. Loeb told universe Today via email, the inspiration for this study came from the first-known interstellar visitor to our solar system – the asteroid "Oumuamua:
"Following that discovery, Manasvi Lingam and I wrote a paper where we showed that interstellar objects like `Oumuamua could be captured through their gravitational interaction with Jupiter and the Sun. The solar system acts as a gravitational "fishing net" that contains thousands of bound interstellar objects of this size at any given time. These bound interstellar objects could potentially plant life from another planetary system and in the solar system. The effectiveness of the fishing net is larger for a binary star system, like the nearby Alpha Centauri A and B, which could capture objects as large as the Earth during their lifetime."
"We expect most objects to likely be rocky, but in principle they could also be icy (cometary) in nature," Ginsburg added. "Regardless of whether they are rocky or icy, they can be ejected from their host system and travel potentially thousands of light-years away. In particular the center of the galaxy can act as a powerful engine to seed the Milky Way."