First-ever interstellar object ‘Oumuamua may be a piece of a planet

The weirdly shaped asteroid and its unusual trajectory raised many questions upon its discovery in 2017

It was a few months ago that I wrote about the second-ever interstellar object — a comet named C/2019 Q4 (Borisov) which was discovered by an amateur astronomer from Ukraine. Using his own telescope, he spotted the comet zipping across the night sky on August 30th of last year. It was a notable discovery, considering C/2019 Q4 (Borisov) was spotted on its way into the Solar system.

The first-ever interstellar object, ‘Oumuamua, was discovered on October 19, 2017, when it was making its way out of our Solar system. Researchers have been intrigued by its unusual shape and trajectory ever since it was spotted in the sky three years ago.

They have been working on figuring out how it got the specific attributes that were observed initially. Some scientists even speculated of it being an alien probe considering the dry surface, unusually elongated shape, and puzzling motion. However, the latter notion was dismissed by a year-long SETI study.

Unlike the most common visitors to our solar system, the asteroids, which are roundish lumps of rock — ‘Oumuamua was a cigar-shaped structure which measured to be 400m (1,300 ft) long, speeding up like a slingshot at 59,000 mph (95,000 km/h) as it went around the sun. The other oddity included the gas it gave off while accelerating like a comet. Later studies confirmed that ‘Oumuamua originated somewhere in the constellation of Lyra.

“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.” ~ Lead Author, Yun Zhang

This illustration shows the tidal disruption process that can give rise to ‘Oumuamua-like objects. (Image credit: NAOC/Y. Zhang)

After a detailed study of all the attributes of ‘Oumuamua, researchers at the Chinese Academy of Sciences and the University of California, Santa Cruz have developed a computer model to explain its shape, trajectory, and its comet-like outgassing.

Using the computer simulation, the team reached the conclusion that ‘Oumuamua is a fragment of a planet or other large rocky object getting its odd shape after going through a “tidal disruption” process (pictured above). The team presumes that the surface of the object melted as it came too close to a star and then recondensed as into a crust that kept its shape as it got flung into deep space.

The same scenario also explains its semi-comet-like characteristics. Comets usually have tails that consist of icy compounds that vaporize once they come close to a star like our sun. While not exactly like that, ‘Oumuamua might have volatile compounds trapped under the surface, which began to vaporize once it passed the Sun.

Of course, this is not the only theory out there trying to explain the origin of ‘Oumuamua. Other explanations include the asteroid being hurtled into deep space by the gravitational influence of a binary star system or a passing star nudging an asteroid out of its orbit. None of these studies, however, have been to explain the properties of ‘Oumuamua in such detail as the current one.

Similar interstellar objects crossing paths with us in the future may provide us further insight into the origin of such objects.

Complete Research was published in the Nature Astronomy.