THERE are "hundreds of billions" of planets orbiting distant stars, a team of Scottish scientists has found.

Researchers from the University of St Andrews said there were at least half as many planets as there were stars in the cosmos, although they cannot currently be seen.

The group spent six years examining data collected by a network of telescopes and the National Aeronautics and Space Administration.

Researchers said the 700 or so planets discovered since 1995 were only a "tiny fraction" of the total out in space, and many more were waiting to be found.

However, they could not say if they were capable of supporting life or were small, rocky planets like the earth.

The team was led by Dr Martin Dominik, a Royal Society university research fellow at St Andrews. He said: "In the past 15 years, we have seen the count of known planets beyond the solar system rising from none to about 700.

"So far, we have detected only a tiny fraction of planets out there. We expect hundreds of billions exist in the Milky Way alone."

A network of telescopes across the southern hemisphere, from Tasmania and Western Australia to South Africa and Chile, were used to observe the skies.

Dr Dominik said the study was like an opinion survey, as it looked at a representative sample, rather than taking an entire count. Only a small number of planets were detected but the researchers said they could estimate their abundance from the sample obtained.

Despite not being able to see the planets, the team were made aware of their presence by the bending of light rays.

The process, known as a gravitational microlensing event, indicates to astronomers that planets are circling the star and impacting on light it emits.

Dr Dominik added: "Our latest results tell us that while we may not see all the planets, wherever in the sky we look, they are there."