Study: ‘Oumuamua’s interstellar object could be a remnant of a” super-Earth “

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 its origin and unusual characteristics ever since. A new article in Nature Astronomy offers a new comprehensive model to explain some of the oddities of the object. ‘Oumuamua, as it is called, may be the fragment of another larger main body, a long-period comet or a disk of debris, perhaps, or even a super-Earth planet, torn apart by tidal forces when too much happened close to its host star.

“Our goal is to create a comprehensive setting, based on well-understood physical principles, to bring all the tantalizing leads together,” said co-author Douglas Lin of the University of California, Santa Cruz. “We demonstrated that ‘Oumuamua-like interstellar objects can be produced through extensive fragmentation of the tides 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, which is part of NASA’s Near-Earth Object Observation program to track asteroids and comets that are close to Earth. The team named it ‘Oumuamua (Hawaiian for “messenger that goes far”). Other telescopes around the world soon came into action, measuring the various characteristics of the object, which turned out to be very strange. For starters, it was accelerating away from our Sun much faster than could be explained by gravity alone. As John Timmer of Ars wrote in 2018:

Initially, its strange orbit had categorized it as a comet, as these tend to have more extreme orbits. But the images did not show any indication of the release of gas and dust, as is typical when a comet approaches the Sun. That image also revealed that it had an elongated, cigar-like shape. Combined with its relatively fast rotation, this would indicate that ‘Oumuamua had to be quite robust, concluding that it was probably an asteroid.

Because it had a hyperbolic, or escape, orbit around the Sun, Oumuamua is unlikely to pass our path again. Thus, astronomers only had a short period of time for the observation to gather as much data about the object as it could before it continued on its merry way.

‘Oumuamua sparked a bit of media excitement again in October 2018, when Harvard astronomer Avi Loeb and his then-postdoctoral fellow Shmuel Bialy submitted a preprint (since its publication) to the Astrophysical Journal. As we reported at the time, much of his analysis discussed the possibility of solar radiation pressure, or the impulse transfer of photons hitting an object. That is the main idea behind “solar sails” that one day could launch spacecraft around our Solar System or beyond. Loeb and Bialy closed their newspaper with a more exotic and highly speculative scenario, suggesting that the object could be a very thin solar sail, specifically, “a fully operational probe intentionally sent to Earth by an alien civilization.”

That short phrase may have released thousands of hyperbolic headlines, but astronomers quite agree that ‘Oumuamua is a natural object and not the result of alien intelligence, despite its strange characteristics. As an astrophysicist Katie Mack noted on Twitter At the time, “What you have to understand is: Scientists are perfectly happy to publish an outrageous idea if it has the slightest * sliver * of a possibility of not being wrong. But until all other possibilities have been exhausted a dozen sometimes finished, even the authors 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, performed various numerical simulations for the types of destructive events that are likely to lead to unusually elongated fragments like ‘Oumuamua. Tidal disruption, the great forces created when a small body passes very close to a much larger one, such as a star, turned out to be the best combination.

Under this scenario, ‘Oumuamua’s father’s body would have been destroyed by these tidal forces, producing numerous elongated fragments that were later ejected into interstellar space. Lin and Zhang also produced thermal models that demonstrate how the surfaces of those fragments would melt when they were close to the star, re-condensing when they were further away to form a stabilizing crust.

“The diffusion of heat during the stellar tidal disruption process also consumes large amounts of volatiles, which not only explains the colors of ‘Oumuamua’s surface and the absence of visible coma, but also clarifies the inferred dryness of the interstellar population, “said Zhang. “However, some high-temperature sublimation volatiles buried below the surface, such as water ice, may remain in condensed form.”

‘Oumuamua is probably not the only object of this type. Last summer, astronomers observed an interstellar comet, named 2I / Borisov, that rushed into our Solar System from the direction of the Cassiopeia constellation. It is highly likely that large swaths of interstellar space could be sprayed with this type of object: ‘Oumuamua and 2I / Borisov are only the first that we have observed.

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 even more interstellar objects by visiting our humble Solar System. If those new objects also exhibit the same unusual properties as’ Oumuamua, that would indicate that Zhang and Lin’s process could be quite extended.

“The expected discovery of a population of ‘Oumuamua-like objects within the Solar System in the coming years … has the potential to transform our thinking and research on minor planets into extrasolar systems,” Dmitri Veras of the University of Warwick, Coventry , in the UK, wrote in a Nature commentary. “The timing would be fortuitous, given the increasing detections of individual planetesimals outside the Solar System. The detailed disruption and thermal models of ‘Oumuamua employed by Zhang and Lin provide a complete and self-consistent history of this object, and a basis for exploring future detections. “

DOI: Astronomy of nature2020. 10.1038 / s41550-020-1065-8 (About DOIs).