Ever since astronomers first began discovering planets outside of the Solar System, dubbed ‘exoplanets’, in the mid-1990s, our picture of the Solar System as a ‘typical’ arrangement of planets and stars has been turned on its head. Among the 5,600 or so exoplanets that we have discovered over the course of the last three decades are scorching hot worlds bombarded by so much stellar radiation that they rain molten metal, planets that race around their stars so fast they can fit several years into a single day and planets squashed by the gravity of their stars so much they have flattened discs. While all of these discoveries have changed our perspective of the Solar System and its planets being ‘typical’ and may have even made our corner of the Milky Way look slightly mundane by comparison, they all share a similar theme: planets orbiting stars – albeit sometimes strangely, violently or chaotically.
In 2012, the universe let humanity know that even this ever-so-familiar concept can’t be taken for granted. That’s the year that astronomers operating the Canada-France Brown Dwarfs Survey discovered the first possible ‘rogue planet’, a cosmic orphan that drifts through the cosmos away from a parent star. Rogue planets go by a range of alternative names, including interstellar, nomad, orphan, starless, unbound or wandering planets, but the more official names for these worlds are free-floating planets
