A distant solar system that looks much like a scale model of our own has been discovered by an international team of astronomers.

The star system — 5,000 light years away — boasts smaller versions of the Sun, Jupiter and Saturn and it is possible that smaller, rocky planets like Earth and Mars could be orbiting closer in.

The discovery suggests that solar systems like ours, with gas giants on the outside and Earth-like worlds nearer the central star, may be common in the Milky Way.

“You could call it luck, but I think it might just mean that these systems are common throughout our galaxy,” said Scott Gaudi, of Ohio State University, who led the research team.

The find also enhances the prospects of finding extra-terrestrial life, as this planetary configuration is considered widely to be the most favourable for its emergence.

Rocky planets like Earth need to be reasonably close to their star to lie in the “Goldilocks zone” in which conditions are neither too hot nor too cold for liquid water and life, while large outer planets like Jupiter and Saturn effectively shield terrestrial worlds from asteroid and comet strikes.

While more than 250 “exosolar” planets orbiting distant stars have now been identified, only 25 stars with more than one planet have so far been found.

The newest of these, named OGLE-2006-BLG-109L, looks much the most similar to the Sun's planetary family, even though it is not yet known whether it has any rocky planets in a similar orbit to Earth.

An Earth-like planet named Gliese 581c, with a diameter three times larger than that of Earth, was discovered last year orbiting a star 20.5 light years away, but the system's other planets do not match ours.

Professor Martin Dominik, of the University of St Andrews, who contributed to the new study using Britain's Liverpool Telescope in the Canary Islands, said: “While most planetary systems around other stars substantially differ from the solar system, a series of recent detections have brought us closer and closer to home.

“Sooner rather than later, someone can be expected to discover an Earth-mass planet orbiting a star other than the Sun - and it could be us.”

The star at the centre of the OGLE-2006-BLG-109L system is about half the mass of the Sun. Its “Jupiter” is 70 per cent of the mass of the real Jupiter, and its “Saturn” is 90 per cent of the mass of the real Saturn. When the masses, orbits and orbital periods of the two planets and the star are compared, they have almost exactly the same ratios as their equivalents in the solar system.

“The fascinating part is that if we scale everything to the mass and brightness of the parent star, the masses of these planets relative to their star, and the amount of sunlight they receive, are close to our own Jupiter and Saturn,” Dr Gaudi said.

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