Smallest 'Earth-like' planet seen

By Pallab Ghosh
BBC science correspondent in Stockholm, Sweden

Scientists are on the lookout for Earth-like planets

European scientists have discovered what they describe as the smallest Earth-like planet orbiting a star outside our Solar System.

The planet is 14 times the size of Earth - not so large that it qualifies as a gas giant - and is close enough to the star that it is unlikely to be icy.

Dr Nuno Santos, of the University of Lisbon, said the new planet could be thought of as "super-Earth-like".

He was speaking at the EuroScience Open Forum in Stockholm, Sweden.

Dr Santos claimed the discovery set a new record for the smallest planet discovered around a solar type star, "further extending European Leadership in the field".

The discovery was made using the highly sensitive Harps spectrograph on the European Southern Observatory's 3.6m telescope at La Silla.

The planet was found to be orbiting the star mu Arae in the southern constellation of Altar. It is the second planet discovered round the star and completes a full revolution in 9.5 days.

Mu Arae was already known to harbour a Jupiter-sized planet with a 650-day orbital period. Previous observations hinted that the giant planet may have a smaller companion much further away.

According to Francois Bouchy, of the Marseille Astrophysics Laboratory, "not only did the Harps measurements confirm what we previously believed to know about this star, but they also showed that an additional planet on a short orbit was present".

This makes mu Arae a very exciting new planetary system.