Astronomers have found a planetary system similar to ours - a Jupiter-like world circling a Sun-like star in roughly the same orbit that Jupiter follows our Sun.
By Dr David Whitehouse
BBC News Online science editor
Of the 100 or so other planetary systems known, this one more closely resembles ours than any other.
Researchers speculate that this system may contain other worlds, such as smaller rocky planets like Earth, either in orbit around the star or around the Jupiter-like world itself.
The planet's parent star, called HD 70642, is slightly too faint to be seen with the unaided eye, but is easily visible in the southern sky using binoculars.
At just 95 light-years away, the gas-giant planet, bathed in the light of a yellow-dwarf star is on our galactic doorstep.
Like Jupiter, its atmosphere could be mottled and streaked with wind patterns and weather systems. Dark-red methane clouds may scurry across its face beneath a high-altitude frosting of bright ammonia crystals.
At its poles, aurora may glisten and lightning bolts pulse across its night-time face.
The planet detected orbiting HD 70642 is not the first Jupiter-class world to be found circling another star. All of the planetary systems found so far contain gas giants like Jupiter.
This is the closest we have yet got to a real Solar System-like planet
Hugh Jones, Liverpool John Moores University
But this Jupiter-like world stirs memories. It circles its parent star at a distance of 467 million kilometres (290 million miles), not a lot different from the 778 million km (483 million miles) that Jupiter is away from our Sun.
The similarities do not end there. This new world circles its star every 6 years; our Jupiter takes 12 years.
Intriguing certainly, but the interest in this system is not principally because of what we know is there, but rather because of what else we suspect may be lurking unseen around the star and its planet.
There could be other worlds, smaller and rocky - possibly Earth-like. These are below the limits of our detectability.
Looking for new Earths
"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," says Hugh Jones of Liverpool John Moores University, UK, who helped discover the new world.
The planet was found using the 3.9-metre (12.8 foot) Anglo-Australian Telescope in New South Wales, Australia. The discovery is being announced at a conference in France.
Prior to the discovery of planets circling other stars, it was predicted that other planetary systems would be similar to our Solar System - giant planets orbiting beyond 4 Earth-Sun distances in circular orbits, and smaller, rocky worlds in inner orbits.
But it turned out to not be like that. Planetary systems are much more diverse than anyone imagined.
The so-called extrasolar planets detected so far are gas-giants that usually lie in elliptical orbits, which would make the existence of habitable rocky planets unlikely.
The discovery of a system that bears a very close resemblance to our Solar System demonstrates that searches for exoplanets are good enough to find Jupiter-like planets in Jupiter-like orbits.
It will encourage astronomers to develop the techniques and space missions required to find smaller Earth-like planets, and look for signs of life on them.
The research reported on Thursday was sponsored by the UK's Particle Physics and Astronomy Research Council (PParc).