If confirmed, the discovery would open the possibility for robotic missions to visit and investigate a piece of another planetary system without ever leaving our stellar home. The findings were published Monday in the Monthly Notices of the Royal Astronomical Society.
Discovered in late 2014 via the Pan-STARRS telescope in Hawaii, the object was provisionally dubbed 2015 BZ509. Scarcely anything is known about it at all, save for its size (about three kilometers wide) and orbit, which is almost identical to Jupiter’s. Almost, that is, save for one important detail—BZ509’s orbit is backwards, or retrograde, meaning it moves in the opposite direction of the prograde orbits of almost everything else circling the sun.
This backward motion goes against the fundamental counterclockwise spin our solar system inherited from more than 4.5 billion years ago, when our star and its planets first coalesced from a whirling disk of gas and dust.