One of the smallest exoplanets yet discovered has just been confirmed as a rocky world, scientists announced.

The planet, called CoRoT-7b, is the first planet beyond our solar system with a proven density similar to Earth's, astronomers say. Most known exoplanets are large gas giants like Jupiter.

"We have indications that other exoplanets could be rocky, but it's the first time that the density of such a planet has been measured," said study team member Claire Moutou of the Laboratoire d'Astrophysique de Marseille in France. "We are really sure it's rocky."