Most Rogue Planets Simply Don't Exist

Though some planets do range free through the Galaxy, there appear to be fewer than first thought.

- Chris Lintott

For the past five years, I’ve been telling audiences at talks that a vast number of free-floating planets exist, out between the stars. I’ve enjoyed ending on the thought that the most typical type of planet may be one which has cut loose from its parent star, slung out into interstellar space. But now new results suggest that might all be wrong.

Such planets can’t be detected by any of the normal methods, which rely on spotting a planet’s effect on its star. Instead, astronomers use a technique that relies on the bending of light by gravity – gravitational lensing. Lensing is most familiar from studies of distant galaxies, their images bent into long, blue arcs by nearby clusters, but here the lensed sources are stars.