New Study Explains Several “Odd Features” of Interstellar Visitor ‘Oumuamua

A large population of 'Oumuamua-like interstellar objects probably exist, and objects like 'Oumuamua could transport matter capable of generating life.

Remember the odd, mysterious object found in 2017 called ‘Oumuamua, the first interstellar visitor posted by mankind? Well, we still don’t know where it car from, what exactly it is, and a new study proves precisely that, although it does offer some new insight on how ‘Oumuamua (1I/2017 U1) got its elongated shape.

New research in ‘Nature Astronomy’ offers the first comprehensive clues to how ‘Oumuamua, the first known interstellar object to visit our solar system, formed –having an extremely elongated, cigar-shaped body.

‘Oumuamua; a weird alien visitor

The lead author of the study, Yun Zhang of the National Astronomical Observatories of the Chinese Academy of Sciences and co-author Douglas NC Lin of the University of California used computer simulations to show how objects like ‘Oumuamua can be formed under the influence of tidal forces like those of Earth’s oceans. Their theory of formation could explain all the unusual characteristics of ‘Oumuamua.

“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,” revealed Lin, professor emeritus of astronomy and astrophysics at UC Santa Cruz.

‘Oumuamua was discovered on October 19, 2017, by the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1) in Hawaii. According to Zhang, ‘Oumuamua is nothing like our solar system. Its dry surface, unusually elongated, and its puzzling movement and odd acceleration even led some scientists to ponder whether ‘Oumuamua was an alien spacecraft sent by an extraterrestrial civilization studying our solar system.

“It is really a mysterious object, but some signs, like its colors and the absence of radio emission, point to ‘Oumuamua being a natural object,” Zhang said.

“Our objective is to come up with a comprehensive scenario, based on well understood physical principles, to piece together all the tantalizing clues,” Lin explained.

Astronomers hoped that the first interstellar object they detected would be a frozen body like a comet. Frozen objects such as those that populate the Oort cloud, a reservoir of comets in the far reaches of our solar system, evolve at very great distances from their host stars.

An artist's rendering of 'Oumuamua. Credit: NASA/JPL-Caltech
An artist’s rendering of ‘Oumuamua. Credit: NASA/JPL-Caltech

These distant objects are rich in volatiles and are often driven from their host systems by gravitational interactions. They are also highly visible due to the sublimation of volatile compounds, which creates the tail of a comet when the sun warms it up. ‘Oumuamua’s dry appearance, however, is similar to rocky bodies like asteroids in the solar system, indicating a different ejection scenario.

Nonetheless, previous studies have suggested that despite ‘Oumuamua’s odd appearance, there should be many objects of similar shape, size, and general dimensions around.

“The discovery of ‘Oumuamua implies that the population of rocky interstellar objects is much larger than we previously thought,” Zhang said. “On average, each planetary system should eject in total about a hundred trillion objects like ‘Oumuamua. We need to construct a very common scenario to produce this kind of object.”

How it got its elongated shape

According to the researchers, when a smaller cosmic body passes close to a much larger one, the smaller body is exposed to the tidal forces of the larger body. These forces can actually treat the smaller object apart, and we’ve seen evidence of that with comet Shoemaker-Levy 9 when it came close to Jupiter.

The process known as tidal disruption can also eject debris into interstellar space, which is actually one of the possible scenarios that could explain the origin of ‘Oumuamua.

However, right until now, whether such a process could account for ‘Oumuamua’s odd characteristics remained a mystery.

To find out, Zhang and Lin performed computer simulations to model the structural dynamics of an object flying in extreme proximity to a star. Their study discovered, perhaps unsurprisingly, that if the object approaches the star at close proximity, the tidal forces could tear the object into extremely elongated fragments that eventually end up being ejected into interstellar space.

In other words, ‘Oumuamua may have been of a  different shape millions of years ago. During one point in its journey, it came close to a massive object which eventually broke it apart, creating its peculiar elongated shape we see today. Then, ‘Oumuamua got expelled, violently, out of its host system and ended up visiting ours.

“The tidal fragmentation scenario not only provides a way to form one single ‘Oumuamua but also accounts for the vast population of asteroid-like interstellar objects,” Zhang said.

The new study supports the theory of a large population of similar objects existing in outer space. Interestingly, since many of these objects could pass within a solar system’s habitable zone, they could also act as transporters of matter that is capable of sparking life on distant alien worlds.

“This is a very new field. These interstellar objects could provide critical clues about how planetary systems form and evolve,” Zhang explained.

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