Interstellar Asteroid Oumuamua’s Weird Cigar-Like Shape Explained

We don’t usually see interstellar space objects in our solar system, but 2017 proved different as scientists spotted Oumuamua — a weird asteroid that came from another star system and zipped through our neighborhood, making headlines all over the globe.

The massive space rock and its speed, around 200,000 mph, drew immediate attention of the scientific community. However, what particularly baffled astronomers was its cigar-like shape. Many thought Oumuamua could be an alien spaceship spying on us, but now, a group of scientists, including astrophysicists at NASA’s Goddard Space Flight Centre, might have an explanation for the object’s weird shape.

In a study published in the journal Monthly News of the Royal Astronomical Society, the team gave insights into Oumuamua’s possible origins with a series of simulations detailing what processes might have come into action as the object got kicked out of its own stellar system.

Usually, space rocks like the one in question are called planetesimals or tiny left-over objects that fail to be part of the group forming new planets. As a result of the chaotic formation, the planet ejects these smaller objects, taking them away or sometimes out of the stellar system.

However, for this specific journey, scientists believe a larger planetesimal might have had some close encounters with other gas giants of the system, so close that the gravitational pull from the planets would have stretched and shredded the object into pieces. This “stretching effect” would have formed a cigar-shaped Oumuamua, instead of a lumpy, normal-looking asteroid.

Oumuamua An artist’s impression of Oumuamua. Photo: ESO/M. Kornmesser

Another interesting thing to note in Oumuamua was its weird behavior.

“Smaller objects that form closer to their stars are too hot to have stable surface ice and become asteroids,” NASA said in a release. “Those that form farther away use ice as a building block and become comets” and shed clouds of gas and dust while flying by a star.

Being an ejected space object, Oumuamua should be icy and behave like a comet, but it did not give away clouds of gas and dust as the scientists expected. This strange dryness could have been a result of a stellar trap, lead study author Sean Raymond explained to Newsweek.

Put simply, it’s plausible that before reaching our solar system, the interstellar object might have been trapped in the orbit of its star, where it would have lost all the material required to produce clouds of gas and dust.

As per Raymond’s simulations, most objects like Oumuamua zipping between stellar systems could also be dry as only 1 percent of planetesimals tear into smaller pieces, a majority of which get trapped in stellar orbits before being ejected out. However, to prove the theory correct, they’ll need more interstellar visitors to study, which could take decades or centuries.

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