Oumuamua, the first space object to visit the Solar System from outside of it, was first thought to be an asteroid, but new research suggested that it was a comet after all.
Oumuamua is now on its way out of the Solar System, raising new questions on whether we will see anything like it ever again.
The Oumuamua Mystery: Asteroid Or Comet?
The first interstellar visitor of the Solar System was spotted in October last year. The cigar-shaped, red-colored object was named Oumuamua, which is the Hawaiian word for "a messenger from afar arriving first."
Oumuamua was so mysterious that astronomers decided to use one of the world's largest telescopes to look at it and check if it is carrying any alien technology. Scientists eventually determined that Oumuamua was an asteroid with an elongated shape caused by gravitational stretching as it left a distant star system.
New study, however, revealed that Oumuamua is not an asteroid, but rather a comet.
Oumuamua Is A Comet, New Research Says
In a new study published in the Nature journal, researchers who have been tracking Oumuamua's trajectory claimed that the interstellar visitor was accelerating as it moves out of the Solar System. The discovery was made through telescopes on Earth and the Hubble Space Telescope.
The increasing speed is not just caused by a gravitational pull but explained by gas that was being released out of the part of Oumuamua that was being warmed by the Sun.
When Oumuamua was first spotted, it did not have a cloud of dust and gas surrounding it like comets. Instead, it looked like it was a huge chunk of rock and metal, similar to asteroids. The study, however, determined that Oumuamua was coated in a layer of grime that insulated its interior. As the Sun warms it up, its ice thaws into gas, like what happens with dry ice on Earth.
"So it's this gas coming off of the comet that gives it a push," said University of Hawaii astronomer and study author Karen Meech, "that acts like little rocket thrusters."
The Oumuamua mystery appears to have been solved, but why did it not look like a comet to begin with? The researchers believe that Oumuamua may have lost its cloud of dust and gas, or it was too faint for astronomers to detect.
Astronomers are now looking forward to the next interstellar visitor, as comets and asteroids may carry information on how other Solar Systems are formed. Hopefully, by then, technology will be advanced enough to send a probe to study the next Oumuamua to unlock the secrets that it will carry.