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ESO / M. Kornmesser
At the end of 2017, our Solar System received its first interstellar visitor: a strange cigar-shaped object that rushes 44 kilometers per second. Scientists have been puzzling over features that were unusual and their own source. A new article in Nature Astronomy offers a new comprehensive model to explain some of the oddities in the article. ‘Oumuamua, as it is called, could be the fragment of another debris disk or a comet, perhaps, or even a world that is super-Earth, torn apart by the forces of the tides by passing too close to its host star .
“Our goal is to think of a comprehensive scenario, in accordance with well-understood physical principles, to put all the tantalizing clues together,” said co-author Douglas Lin of the University of California at Santa Cruz. “We reveal that Oumuamua-like interstellar objects can be generated through extensive fragmentation of the tides during close encounters of their parent bodies using their host stars, and then ejected into interstellar space.”
The interstellar thing was first discovered by the University of Hawaii’s Pan-STARRS1 telescope, a part of NASA’s Near-Earth Object Observation program to monitor asteroids and comets that are close to Earth. The team called him Oumuamua (Hawaiian for “messenger who goes far”). Telescopes around the planet kicked in, measuring the object’s various features, which turned out to be strange, really. For starters, it was accelerating away from our Sun that could be explained only by gravity. As John Timmer of Ars wrote in 2018,
Originally, its strange orbit had categorized it as a comet, as these tend to have more intense orbits. But the images did not show any signs of gas and dust being released, when a comet approaches the Sun, as is normal. That image also revealed that it had an elongated shape, similar to a cigar. Combined with its relatively fast turn, this would indicate that Oumuamua had to be quite robust, leading to the conclusion that it was probably an asteroid.
Since it had a hyperbolic, or escape, orbit around the Sun, Oumuamua is unlikely to cross our path. So astronomers had a short time to gather as much information as they could about the thing before it went on its way.
Enlarge / / This illustration indicates the procedure of interruption of the tide that can give rise to objects similar to Oumuamua.
NAOC / Y. Zhang
Um Oumuamua sparked a bit of excitement in the media in October 2018, when Harvard astronomer Avi Loeb and his then-postdoctoral fellow Shmuel Bialy sent a preprint (from print) to the Astrophysical Journal. As we report at this time, much of the analysis discussed the potential of solar radiation pressure, or the impulse transfer of photons hitting an object. That alone is the main idea behind the “solar sails” that will one day propel spacecraft around our Solar System or beyond. Loeb and Bialy closed their newspaper in a more exotic but highly speculative situation, suggesting that the object could be a very thin solar sail, especially “a fully operational probe intentionally sent to the Earth area by an alien culture.”
That short phrase may have released thousands of hyperbolic headlines, but astronomers quite agree that Oumuamua is a natural object rather than the result of alien intelligence, despite its strange features. From astrophysicist Katie Mack noted on Twitter right now, “what you should realize is: scientists’ are perfectly pleased to publish an outrageous idea if it has the slightest chance * of not being wrong. But until all other possibilities have been exhausted a dozen times, even writers probably don’t believe it. ”
And that leads us to this last article, which details a comprehensive theory for the formation of ‘Oumuamua’ that explains all its strange characteristics. Lin and his co-author Yun Zhang of the National Astronomical Observatories of the Chinese Academy of Sciences conducted several numerical simulations for the types of harmful events that are likely to lead to fragments that were unusually elongated, such as “Oumuamua.” Tidal disruption: The forces generated when a small body moves close to you, like a star, proved to be the ideal match.
Enlarge / / Something like Oumuamua made by a simulation of the tidal disturbance scenario suggested by Zhang and Lin.
NAOC / Y. Zhang (desktop: ESO / M. Kornmesser)
In this situation, the body of Oumuamua’s parents would have been torn from these tidal forces, forming numerous elongated fragments that were later ejected into interstellar space. Zhang and Lin also produced models showing that the surfaces of these fragments would melt when they were close together if they were further away to create a crust that stabilized, condensed again.
“The heat diffusion during the stellar tidal disruption process also consumes considerable amounts of volatiles, which not only explains the colors of the Oumuamua surface and has no visible coma, but also clarifies the inferred dryness of the interstellar inhabitants “Zhang said. “But some high-temperature sublimation volatiles buried below the surface, like water ice, may remain in condensed form.”
Um Oumuamua is probably not the only object of this type. Astronomers observed an interstellar comet rushing into our Solar System. It is highly likely that large swaths of interstellar area could be sprayed with these types of elements. Oumuamua and 2I / Borisov are alone.
When the Vera C. Rubin Observatory comes online later this year (if you want the coronavirus) in Chile, astronomers are optimistic that we will discover more interstellar objects by visiting our humble Solar System. If those new things also exhibit identical properties that are unusual like ‘Oumuamua, which would imply that Lin and Zhang’s procedure could be quite widespread.
“The expected discovery of a population of ‘Ouamua-like objects within the Solar System for years to come … has the ability to change our thinking and analysis of minor planets within extrasolar systems,” Dmitri Veras of the University of Warwick, Coventry in the UK wrote in a Nature comment. “The timing could be fortuitous, given the increasing detections of planetesimal people outside the Solar System. The deep disturbance and thermal versions of ‘Oumuamua used by Zhang and Lin offer a complete and consistent history of the object, and a basis for investigating future detections. ”
DOI: Astronomy of nature2020. 10. 1038 / s41550-020-1065-8 (About DOIs).
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