'Rogue Planet' Spotted Lost In Space?

Astronomers have discovered a lonely wanderer in space: a planet that appears to have no guiding star.

The concept of free-floating planets has been proposed before, with other possible candidates for objects identified as such. But scientists have found it difficult to rule out whether any of the other objects were actually planets, or brown dwarfs -- stars that failed to accumulate enough mass to sustain the hydrogen fusion reactions at their cores that would allow them to really shine.

Now researchers using telescopes at the European Space Observatory think that a new object called CFBDSIR2149 could fit the bill of a so-called “rogue planet.” They announced the discovery in a paper published Wednesday in the journal Astronomy & Astrophysics.

The object, with a mass of about 4 to 7 times that of Jupiter, inhabits a stream of young stars called the AB Doradus Moving Group. The stars in this group are thought to have all formed at the same time, and the fact that CFBDSIR2149 is moving along with them means it is likely the same age, allowing researchers to estimate the object's age.

Because it is not orbiting a star, scientists can also discern more about this possible planet than many other exoplanets.

“Looking for planets around their stars is akin to studying a firefly sitting one centimeter away from a distant, powerful car headlight,” French researcher Philippe Delorme, lead author of the study, said in a statement Wednesday. “This nearby free-floating object offered the opportunity to study the firefly in detail without the dazzling lights of the car messing everything up.”

It's possible that the likely “rogue planet” once orbited a star, but was kicked out. Or, possibly, it formed on its own, like small stars and brown dwarfs, and has always been alone. It's possible that there could be just as many orphan planets as there are stars, treading their own paths, the scientists say.

“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,” Delorme says. “If this little object is a planet that has been ejected from its native system, it conjures up the striking image of orphaned worlds, drifting in the emptiness of space.”

Now Delorme and his colleagues will work on confirming that CFBDSIR2149 is truly a free-floating planet. If it is, then the object could be used as a benchmark that could help researchers understand the physics of other, yet-to-be discovered rogue worlds.