In contrast, however, to these Roasters, Eccentric Giants and Transitters, a planet orbiting the star Mu Arae, and two others reported at about the same time in 2004, are smaller than their predecessors and could be made largely of rock ( although much larger than Gliese 581).

The planet around Mu Arae weighs at least 14 times as much as the Earth and is scorchingly close to its star, completing an orbit every 9.5 days.

In 2005, a ‘super-Earth’ was found orbiting Gliese 876, 15 light years away in the constellation Aquarius. It has about a third the Sun’s mass, and has two Jupiter-size worlds orbiting it. At the time it was the smallest star known to have planets.