Scientists have identified three new planets around a star they already suspected of hosting a trio of worlds.

It means this relatively nearby star, Gliese 667C, now has three so-called super-Earths orbiting in its "habitable zone".

This is the region where temperatures ought to allow for the possibility of liquid water, although no-one can say for sure what conditions are really like on these planets.

Gliese 667C is 22 light-years away.

Astronomers can see it on the sky in the constellation of Scorpius (The Scorpion).

Previous studies of Gliese 667C had established there were very probably three planets around it, with its habitable zone occupied by one super-Earth - an object slightly bigger than our home world, but very probably with a rocky surface.

Now, a team of astronomers led by Guillem Anglada-Escude of the University of Göttingen, Germany, and Mikko Tuomi, of the University of Hertfordshire, UK, has re-examined the system and raised the star's complement of planets.

The researchers used a suite of telescopes including the 3.6m telescope at the Silla Observatory in Chile. This incorporates the high-precision Harps instrument. Harps employs an indirect method of detection that infers the existence of orbiting planets from the way their gravity makes a parent star appear to twitch in its motion across the sky.