When we hear about the discovery of new planets outside the Solar System, they're usually orbiting a star of some description. Scratch that -- they're always orbiting a star. So you can understand why PSO J318.5-22, a planet that appears to be sailing freestyle through space, is an exciting piece of extrasolar news.
The planet was discovered by Pan-STARRS 1, a wide-field survey telescope in Maui, according to a press release from the Institute of Astronomy at the University of Hawaii.
Interestingly, PSO J318.5-22, despite being all by itself in the great black void, was easier to spot than a regular planet, as the light from stars makes observing the objects that orbit them difficult.
Continued study of PSO J318.5-22 revealed it is low-mass, with the characteristics of a gas giant and about 80 light years from Earth (making it the closest rogue planet we've seen). As to its origins, the money is on a star in Beta Pictoris moving group.
How it managed to end up starless is anyone's guess -- if it had a parent at all -- thought it's not the only rogue out there.
My theory? It's hollow inside and full of aliens, though that could be the tin-foil hat talking.
Lead image: MPIA/V. Ch. Quetz Body image: N. Metcalfe & Pan-STARRS 1 Science Consortium