The galaxy is getting messy: astronomers have found planets that meander around space without neatly orbiting a star. This contradicts everything we learned in our 8th grade science class. Nevertheless, The New York Times reports that scientists have noted at least 10 Jupiter-sized planets (that's the big one pictured above) roaming around the Milky Way that may not be constrained by an orbit. Their hunch is that billions more are out there.
The research, originally reported in the academic journal Nature, points out that the planets "have no host stars that can be detected within about ten astronomical units by gravitational microlensing." The Times translates this statement by observing that astronomers aren't sure if "planets in question are in fact floating free or just far from their stars."
The existence of what've been deemed "free-floaters" may give credence to the idea the planets are thrown out of their neat orbit during formation. The Associated Press writes:
Scientists believe planets are formed when disks of dust that orbit stars form clumps, so that these clumps - the planets - remain in orbit. Maybe the newfound objects started out that way, but then got tossed out of orbit or into distant orbits by the gravitational tugs of larger planets, the researchers suggest.
So there's a giant, galaxy-wide, gravitational tug-of-war acting on these floating rocks. And one of those planets that does orbit a star, but is not Earth, has recently been flagged as possibly Earth-like enough to host life.