It's long been speculated that there may be planets whizzing through space without a sun to orbit, and now we may have found the first confirmed case.
It's been a long standing theory that planets on occasion become ejected from their solar systems. Several objects have been found since the 1990's which have possibly met this fate, but until now, all such objects have been too close to a star to observe properly. It's unknown if these objects really are planets, or failed stars known as Brown Dwarves.
Now though, Philippe Delorme and his team from Institut de planétologie et d'astrophysique de Grenoble, CNRS/Université Joseph Fourier, France, have found an object which they can confirm is an ejected planet by using the ESO's Very Large Telescope and the Canada-France-Hawaii Telescope. The planet, known as CFBDSIR2149 …we'll call it Charlie for short, is supposedly four to seven times the size of Jupiter, but is bluish in hue and looks more like Neptune.
Artist's depiction of Charlie if illuminated by a star
Delorme's team explains their conclusions: "The team's statistical analysis of the object's proper motion; its angular change in position across the sky each year, shows an 87% probability that the object is associated with the AB Doradus Moving Group, and more than 95% probability that it is young enough to be of planetary mass, making it much more likely to be a rogue planet rather than a small "failed" star."
The AB Doradus Moving Group is a group of around 30 stars which are all traveling at the same velocity, and have similar age and composition. The planet most likely used to orbit one of these stars, before being thrown out. It's not easy to throw a planet out of it's star system, but gravitational forces and interacting bodies could certainly do it. Another planet in the star system might have had an orbit that took it too close to Charlie, and slingshot it (him?) out of the system.