The planets beyond our solar system keep getting weirder and weirder. First came word of Jupiter-sized worlds that roast improbably close to their parent stars. Now astronomers Phil Lucas of the University of Hertfordshire and Patrick Roche of Oxford University say they have spotted planets that travel alone through the dark coldness of space.
The researchers found these solo travelers by training the United Kingdom Infrared Telescope's Fast Track Imager on a group of very young stars in the Orion nebula, 1,500 light-years from Earth. Among this crowd, the camera picked out the feeble infrared glow of 150 objects too small and cool to be stars. Thirteen of them appear to be planets, Lucas says. He estimates they have masses roughly eight times that of Jupiter, which implies that they are huge bodies with deep atmospheres. Lucas and Roche suspect these planets grew directly out of a cloud of cold gas and dust—not from a disk surrounding an infant star, the way normal planets do. "We can't rule out the possibility that some might have been flung out of a solar system, but it looks like they have always been free-floating," says Lucas.