This artist's conception illustrates a giant planet floating freely without a parent star. Astronomers recently uncovered evidence for such lone worlds, thought to have been booted from developing star systems. The sun may have captured such a planet, which new work shows may reside at the edge of the solar system.
This artist's concept illustrates the preferred model for explaining ALMA observations of Beta Pictoris. At the outer fringes of the system, the gravitational influence of a hypothetical giant planet (bottom left) captures comets into a dense, massive swarm (right) where frequent collisions occur.