The first interstellar interloper to be detected by our telescopes has been puzzling astronomers ever since it was first spotted in October 2017 by the Pan-STARRS-1 telescope at the Haleakala Observatory in Hawaii.
Initially dubbed a comet, 'Oumuamua — whose moniker translates as "messenger from afar arriving first" in Hawaiian — was confirmed as an asteroid a month later and classified as the first in a new class of objects which were presumed to be interstellar asteroids.
As the Inquisitr previously reported, the mysterious object that swung by our solar system from very far away looks like nothing we've seen before. The 400-meter (0.25-mile) long space rock is extremely elongated and could be up to 10 times as long as it is wide — which is uncommon for both asteroids and comets, notes Science Alert.
At some point toward the end of 2017, 'Oumuamua's bizarre, cigar-shaped appearance even gave rise to the speculation that this one-of-a-kind space object might be an alien spaceship. But radio scans of the enigmatic space rock revealed no signs of alien technology, the Inquisitr reported in December.
Now, a new study published today in the journal Nature has finally cracked the mystery of 'Oumuamua's identity, announcing that our interstellar interloper is a comet after all.
Conducted by an international team of researchers, the study took a close look at 'Oumuamua's path through our solar system and uncovered that the object previously described as an interstellar asteroid actually moves like a comet, reports the Verge.
Propelled By Loss Of Gas
According to The Guardian, the team studied the interstellar object's trajectory through to January and discovered that it's accelerating too fast for it to be an asteroid. In fact, the only way to account for its current speed is if 'Oumuamua were a comet being pushed through our solar system by the gas that seeps out of its sun-warmed end."The motion of all celestial bodies is governed mostly by gravity, but the trajectories of comets can also be affected by non-gravitational forces due to cometary outgassing," the authors wrote in their paper.
This process, common in comets as their ice thaws to gas under the heat of the sun, acts like a rocket thruster and propels the object faster and faster, explains study co-author Karen Meech, an astronomer at the University of Hawaii.
Team leader Marco Micheli, an astronomer at the European Space Agency's SSA-NEO Coordination Centre in Italy studying near-Earth objects, said that neither solar radiation nor the magnetic field of the solar wind is behind 'Oumuamua dizzying speed — which can't be explained by the normal interactions of an asteroid with the gravity of the sun, the moon, and the nearby planets.
"We analyzed other possible explanations in detail, and each of them turned out not to work, either because the effect was too weak, or because its behavior did not match the data."These findings support the results of an earlier study published in December in the journal Nature, which concluded that 'Oumuamua may be a comet even if it doesn't behave like one.
An Unusual Comet
This latest study makes a compelling case that our interstellar visitor is actually a comet in disguise, despite the fact that it lacks the iconic comet tail, also known as a coma — which is why the object was cataloged as an asteroid in the first place, the Inquisitr reported last year.While most comets are shrouded in a cloud of gas and dust, 'Oumuamua lacks this feature as well. Yet the researchers have come up with three possible explanations as to why that is.
In one scenario, the enveloping cloud was stripped away from this interstellar comet, leading to its weird appearance. Another possibility is that astronomers simply didn't see it, as Meech points out that space gas is actually difficult to pick up with a telescope.
The third explanation is that 'Oumuamua is unlike any other comet we've ever known and displays a different chemical makeup. For instance, the interstellar traveler has no trace of cyanide gas, says Meech.
"It emits light very strongly in blue colors, and no one saw it. If the chemistry was the same, we should have seen some," she explains.