They're outcasts on a galactic scale, rebels without a star: Astronomers think they have discovered 10 massive planets that defy a standard definition of what it means to be a planet: They orbit no star. What's more, the astronomers believe there are many, many more roaming free about the Milky Way, possibly twice the number of stars in the galaxy, reports Time. The new findings could shed more light on how planets form.
"The implications of this discovery are profound," writes a member of the Center for Astronomy in Germany in an accompanying Nature article. Scientists have long speculated that such rogue planets could exist, with one theory being that they got flung away from their own systems because of a too-close-encounter with another planet, explains Bloomberg. Astronomers used a process known as gravitational microlensing to detect the Jupiter-sized objects, and Space.com has more on how it works. (Read more planets stories.)