Orphan planets.

Space Orphan or rogue planets have become more than a theoretical possibility reports National Geographic. Scientists searching for dwarf planets, may have stumbled upon one such object, drifting through space:

"Compared with other potential homeless planets, the new candidate is also older, colder, and much closer to Earth—approximately 130 light-years away ...

"Called CFBDSIR2149, the suspected orphan planet appears to reside in a group of young stars, though it isn't gravitationally linked to any of them. This affiliation with the so-called AB Doradus Moving Group helped scientists estimate the planet's age: 50 to 120 million years old."