Astronomers have for the first time found a rogue planet that appears to be wandering through space on its own, unattached to any star.
"Although theorists had established the existence of this type of very cold and young planet, one had never been observed until today," says Étienne Artigau, an astrophysicist at University of Montreal (UdeM).
Similar objects have been sighted before, but have never been confirmed, as astronomers have not been able to put an age to them. Astronomers use the object’s age to determine if they are really planets rather than brown dwarfs – ‘failed’ stars that resemble planets. The sighting also raises the tantalising possibility that such worlds could be more common than we think, maybe even as numerous as normal stars.
"Over the past few years, several objects of this type have been identified, but their existence could not be established without scientific confirmation of their age," explained Jonathan Gagné, a doctoral student of physics at UdeM.
Because the planet's only around 100 light years from us and there's no dazzling bright light from a nearby star, the astronomers were also able to study its atmosphere in great detail.
"Looking for planets around their stars is akin to studying a firefly sitting one centimetre away from a distant, powerful car headlight," says Philippe Delorme, of the Institut de planetologie et d'astrophysique de Grenoble. "This nearby free-floating object offered the opportunity to study the firefly in detail without the dazzling lights of the car messing everything up."
These objects are important, as they can either help us understand more about how planets may be ejected from planetary systems, or how very light objects can arise from the star formation process, he added.
The homeless planet may be associated with the AB Doradus Moving Group, a wandering group of stars that drift through space together. If confirmed, the homeless planet’s association with this group would confirm that it is young. It would also allow astronomers to assume other information about its features such as the temperature, mass and the make-up of its atmosphere.
However if CFBDSIR2149 is not associated with the AB Doradus Moving Group it will be much more difficult to determine its properties, and it may still be classified as a brown dwarf.
"Further work should confirm CFBDSIR2149 as a free-floating planet," concludes Philippe Delorme.