It’s a bird! It’s a plane! It’s an asteroid! It’s a weird spaceship from another galaxy! It’s a comet! It’s … Oumuamua! The interstellar visitor didn’t stay long but it has captivated the hearts and minds and computer models of astronomers and space scientists worldwide who want to know what it is. Researchers watching the trailing end of the cigar-shaped visitor as it left the solar system noticed that it was accelerating. While it could have just been trying to get away from the all of the chaos it saw on Earth, the real reason seemed to be that gas coming off of the back end was pushing it to a slightly higher speed … a trait that is commonly seen on … sorry, it’s too late to place your bets … comets!
“After ruling out solar-radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object, and geometric effects originating from ‘Oumuamua potentially being composed of several spatially separated bodies or having a pronounced offset between its photocentre and centre of mass, we find comet-like outgassing to be a physically viable explanation, provided that ‘Oumuamua has thermal properties similar to comets.”
A team led by Marco Micheli, a European Space Agency astronomer, released their study this week in the journal Nature. The acceleration of Oumuamua was actually expected since it would be affected by the gravitational pulls of the Moon and outer planets, but the speed at which it was moving could not be attributed to gravity alone.
“It’s an unusual comet, and that’s pretty exciting.”
Karen Meech, an astronomer at the University of Hawaii in Honolulu and a team member, explained to Hawaii's KHON that the unusual lack of dust and ice on Oumuamua meant it didn’t have a tail and that initially led observers to think it was a rocky asteroid rather than an icy comet. In addition, Meech says astronomers were looking for evidence of cyanide, which gives comets a blue hue. They didn’t see it, which means that Oumuamua is still a comet but one with a different chemical composition that those passing thought the solar system before.
If you’re looking for a career exploring the stars and you’re too tall or too scared to be an astronaut, Meech recommends astronomy as the job of the future.
"This is the first time we've ever seen anything like this. Astronomers have been predicting this for decades, so it was very exciting to see the first one come through. I think the Pan-STARRS in particular is going to start to see a lot more of these with the second telescope now starting its survey, so it's an exciting time to be an astronomer."
Exciting, yes … unless you’re the astronomer who spots the deadly asteroid or comet heading straight for Earth.