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takyon writes:

Tracking the interstellar object 'Oumuamua to its home

A team of astronomers led by Coryn Bailer-Jones of the Max Planck Institute for Astronomy has tracked the interstellar object 'Oumuamua to several possible home stars. The object was discovered in late 2017 – this was the first time astronomers have been able to observe an astronomical object from another star system visiting our own Solar System. Bailer-Jones and his colleagues used data from the ESA astrometry satellite Gaia to find four plausible stars where 'Oumuamua could have begun its long journey, more than a million years ago. [...] Earlier studies had attempted similar reconstructions of 'Oumuamua's origin, but had not come up with plausible candidates.

These earlier studies were missing a crucial ingredient: in June 2018, a group led by ESA astronomer Marco Micheli had shown that 'Oumuamua's orbit within the Solar System is not that of an object in free fall, that is, of an object moving exclusively under the influence of gravity. 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. Although weak - the outgassing was not visible on images like it is with comets close to the Sun - it is too large to be ignored when back-tracking the orbit. The new study by Bailer-Jones and colleagues takes into account how 'Oumuamua's orbit has changed as the object passed close to the Sun, giving the astronomers a precise estimate of the direction the object came from originally, as well as the speed at which it entered our Solar System.

[...] 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.

'Oumuamua.

Also at Space.com.

Plausible home stars of the interstellar object 'Oumuamua found in Gaia DR2

Previously: 'Oumuamua Likely Originated in the Local Association (Pleiades Moving Group)
'Oumuamua Outgasses Like a Comet

Original Submission

EventH0rizon writes:

Two Harvard astronomers have suggested that the interstellar object that passed through our solar system in late 2017 and early 2018 could have been part of an alien spacecraft.

Shmuel Bialy and Abraham Loeb, two astronomers from the Harvard Smithsonian Centre for Astrophysics, suggested the cigar-shaped object — given the Hawaiian name 'Oumuamua, which NASA notes "means a messenger from afar arriving first" — could have been a discarded light sail of extra-terrestrial origin, perhaps sent here on purpose.

From the paper:

We explain the excess acceleration of `Oumuamua away from the sun as the result of the force that the sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimeter in thickness but tens of meters in size. This makes the object lightweight for its surface area and allows it to act as a light-sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the solar system)."

It's not hard to find plenty of the usual skepticism, much of which seems to center on whether or not the object outgassed on the way into our solar system, and it's shape. The gist of the Harvard paper seems to be that the object would need to be extremely thin and not at all like the rocky artists rendering that has commonly been used in stories to date.

What do Soylentils think of this latest twist?

Original Submission

upstart writes in with an IRC submission for SoyCow1:

Study: 'Oumuamua interstellar object might be remnant of a "super-Earth":

In late 2017, our Solar System received its very first interstellar visitor: a bizarre cigar-shaped object hurtling past at 44 kilometers per second. Scientists have been puzzling over its origin and unusual characteristics ever since. A new paper in Nature Astronomy offers a new comprehensive model to explain some of the object's oddities. 'Oumuamua, as it is called, may be the fragment of another, larger parent body—a long-period comet or debris disk, perhaps, or even a super-Earth planet—torn apart by tidal forces as it passed too close to its host star.

"Our objective is to come up with a comprehensive scenario, based on well understood physical principles, to piece together all the tantalizing clues," said co-author Douglas Lin of the University of California, Santa Cruz. "We showed that 'Oumuamua-like interstellar objects can be produced through extensive tidal fragmentation during close encounters of their parent bodies with their host stars, and then ejected into interstellar space."

The interstellar object was first discovered by the University of Hawaii's Pan-STARRS1 telescope, part of NASA's Near-Earth Object Observations program to track asteroids and comets that come into Earth's vicinity. The team dubbed it 'Oumuamua (Hawaiian for "messenger from afar arriving first"). Other telescopes around the world soon kicked into action, measuring the object's various characteristics, which turned out to be very odd, indeed. For starters, it was accelerating away from our Sun much faster than could be explained by gravity alone.

[...] And that brings us to this latest paper, detailing a comprehensive theory for 'Oumuamua's formation that accounts for all of its strange characteristics. Lin and his co-author, Yun Zhang of the Chinese Academy of Science's National Astronomical Observatories, ran several numerical simulations for the kinds of destructive events most likely to lead to unusually elongated fragments like 'Oumuamua. Tidal disruption—the large forces created when a small body passes very close to a much larger one, like a star—proved to be the best match.

Related
Interstellar object 'Oumuamua believed to be 'active asteroid'

Journal Reference
Yun Zhang, Douglas N. C. Lin. Tidal fragmentation as the origin of 1I/2017 U1 ('Oumuamua), Nature Astronomy (DOI: doi:10.1038/s41550-020-1065-8)

Original Submission

upstart writes in with an IRC submission for RandomFactor:

Scientists determine 'Oumuamua isn't made from molecular hydrogen ice after all:

The debate over the origins and molecular structure of 'Oumuamua continued today with an announcement in The Astrophysical Journal Letters that despite earlier promising claims, the interstellar object is not made of molecular hydrogen ice after all.

The earlier study, published by Seligman & Laughlin in 2020—after observations by the Spitzer Space Telescope set tight limits on the outgassing of carbon-based molecules—suggested that if 'Oumuamua were a hydrogen iceberg, then the pure hydrogen gas that gives it its rocket-like push would have escaped detection. But scientists at the Center for Astrophysics | Harvard & Smithsonian (CfA) and the Korea Astronomy and Space Science Institute (KASI) were curious whether a hydrogen-based object could actually have made the journey from interstellar space to our solar system.

"The proposal by Seligman and Laughlin appeared promising because it might explain the extreme elongated shape of 'Oumuamua as well as the non-gravitational acceleration. However, their theory is based on an assumption that H2 ice could form in dense molecular clouds. If this is true, H2 ice objects could be abundant in the universe, and thus would have far-reaching implications. H2 ice was also proposed to explain dark matter, a mystery of modern astrophysics," said Dr. Thiem Hoang, senior researcher in the theoretical astrophysics group at KASI and lead author on the paper. "We wanted to not only test the assumptions in the theory but also the dark matter proposition." Dr. Avi Loeb, Frank B. Baird Professor of Science at Harvard and co-author on the paper, added, "We were suspicious that hydrogen icebergs could not survive the journey—which is likely to take hundreds of millions of years—because they evaporate too quickly, and as to whether they could form in molecular clouds."

Journal Reference:
Thiem Hoang, Abraham Loeb. Destruction of Molecular Hydrogen Ice and Implications for 1I/2017 U1 ('Oumuamua) [open], The Astrophysical Journal Letters (DOI: 10.3847/2041-8213/abab0c)

Original Submission