WHEN is a large planet not a large planet? When it’s two smaller ones in disguise, a possibility that suggests we may have found a world the size of Earth without realising.
Guillem Anglada-Escudé of the University of Barcelona, Spain, and colleagues re-examined why certain stars wobble. This back-and-forth motion is often attributed to the gravitational pull of a large planet in a close, eccentric orbit. However, their mathematical models suggest the wobble of some stars could instead be the signature of a pair of smaller planets on circular paths, one orbiting exactly twice as fast as the other.
