The interstellar visitor Oumuamua is a comet after all

An artistic illustration of the interstellar object ‘Oumuamua, which seems to be outgassing material. Scientists suspect that a comet after all, and not an asteroid.

(ESA/Hubble, NASA, ESO, M. Kornmesser)

It turns out that ‘Oumuamua, our first known interstellar visitor, is a comet.

This cosmic object was first discovered in 2017 by researchers with the Panoramic Survey Telescope Rapid Response System (Pan-STARRS). The strange, cigar-like shape, the lack of both a tail and a coma, it is difficult to categorize — some even suggested that this could hold extraterrestrial life. It has so far been classified as a comet, classified as an asteroid, and even in a new ‘interstellar objects” class.

‘Oumuamua, since the discovery, it is very difficult for researchers to study and understand, because, since “this was actually a weak object … we had very little time to observe it,” Karen Meech, an astronomer at the University of Hawaii and co-author on the new work, told But now, in an article published today (27 June) in the journal Nature, researchers seem to have concluded that the mysterious interstellar body is a comet. Scientists still do not know where the dark-red, 2,624-foot-long (800-meter) object came from, but at least part of the mystery is now to rest. [‘Oumuamua: The solar system, 1st Interstellar Visitor Explained in Pictures]

Tumbling through our solar system, ‘Oumuamua the movement and behaviour along this journey has led investigators to their conclusion. They found that the ‘bow’ Oumuamua traveled along may not be fully explained by the gravity of the sun, the planets and other solar system objects. So, as the researchers explained in the new paper, part of the object’s acceleration is not caused by gravity.

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The classification of the object as a comet puts her bow movement and nongravitational acceleration, such as comets can be powered by the gas that they release.

There are other possible explanations for this acceleration, such as magnetic interaction with the solar wind, the pressure of the solar radiation, and the forces of drag and friction. But the researchers excluded.

This leaves the remaining explanation that ‘Oumuamua is partially powered by gas, which would indicate that it is a comet.

Meech said that this study is “conclusive ending” the mystery of what this object really is, while adding that there has never been a one hundred percent guarantee on everything.”

These researchers “infer that it is a comet on the basis of all the available evidence, but there is no other explanation,” Meech said. She added that, if they wanted the concrete proof that it is a comet, which they would have needed to see “a tail of dust and gas, but that was simply not possible in this case.”

Still, ‘Oumuamua is anything but a standard comet. It lacks a coma, the cloud of gas and dust that usually surrounds a comet’s nucleus, and the researchers did not have to be a classic comet tail. The object also has a noticeably unique look. So, with the knowledge that they have, the researchers found that ” Oumuamua must be a comet.

The main remaining mystery about ‘Oumuamua is its origin. Researchers still do not know where the object came from, according to Meech, knowing that the object has nongravitational motion will make it even more difficult to figure out the source.

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