Astronomers have pinpointed a planetary system which resembles our own solar system, raising hopes of the discovery of Earth-like planets capable of bearing life.
For the first time, they have identified a Jupiter-like planet, orbiting a star like the sun, at much the same distance from the parent star as Jupiter is from the sun.
The star, known only as HD70642, is 90 light years away in the constellation Puppis. Scientists estimate this star is orbited, once every six years, by a planet about twice the mass of Jupiter.
"This is the closest we have yet got to a real solar-system-like planet, and advances our search for systems that are even more like our own," said Hugh Jones of Liverpool John Moores University, England, who announced the discovery on Thursday at a conference on extrasolar planets in Paris.
He and colleagues used a 3.9m Anglo-Australian telescope at Siding Springs in New South Wales for the work.
Until 1995, there was no evidence at all of planets orbiting other stars. Since the first dramatic discovery eight years ago, researchers have identified more than 100 planetary systems within 150 light years of Earth.
No one has seen any of these planets: researchers infer the presence of an orbiting planet from a kind of wobble in the light from the parent star. The technique is reliable but has limitations.
Earth is known to astronomers as a "Goldilocks" planet, not so far away that water freezes, not so close that it boils: in fact, just right for life to evolve.
The excitement over HD70642 is because its orbital system leaves room for a series of rocky planets much nearer the parent star. It is the first evidence so far that other stars could be encircled by planets like earth.
"It is the exquisite precision of our measurements that lets us search for these Jupiters -- they are harder to find than the more exotic planets found so far," said Alan Penny of the Rutherford Appleton Laboratory in Oxfordshire, England.
The universe contains perhaps 100 bilion galaxies, each containing 100 billion stars. Researchers can only hope to study the nearest of these. Astronomers backed by the US National Science Foundation are working to put all 2,000 of the nearest sun-like stars under scrutiny, out to distances of 150 light years.
In 2008, a new generation of telescopes will be powerful enough to detect the transit of Earth-sized planets with a one-year orbit.
And in 2015, Nasa and Europe could launch a flotilla of spacecraft, all capable of focusing with exquisite accuracy on stars most likely to have rocky planets in their inner zones, in the hope of seeing reflected planetary light directly.