Hugh Jones of Liverpool John Moores University said his team had discovered the system, illuminated by a star dubbed HD 70642, some 94 light-years from Earth. Jones was presenting the finding at a conference at the Paris Astrophysics Institute Thursday.
The star is similar to the sun in structure and brightness and appears to be about the same age, Jones said. The planet is traveling around the star in an orbital path similar in shape and distance to the one that Jupiter follows around our Sun.
Those similarities have led the planet-hunters in Jones' team of British, Australian and American scientists to conclude that they have tumbled upon something exciting — the possibility of finding another Earth in the Milky Way galaxy.
"We are honing in on the search for planets like the Earth," said Alan Penny of Rutherford Appleton Laboratory west of London.
Nearly 110 extrasolar planets — planets orbiting stars other than the sun — have been found within the past decade, but none really resembled our solar system until now, Penny said.
"This is the first one that is really like our own solar system of the 110 that we've found," Penny said in a telephone interview. "We think it's a substantial step on the way to finding another Earth."
No large planets have been found between the Jupiter-like planet and the star, leading scientists to conclude that an Earth-sized planet could be nestled in between. If a large planet were present, its gravitational pull would throw anything the size of Earth out of the system, Penny said.
The discovery was found by measuring the star's wobble caused by the gravity of the planet. The technique measures the very slight wobble of a central star and then uses the magnitude of this motion to determine the presence of orbiting planets, the size and shape of their orbits and their mass. The technique works only for larger planets and cannot detect those much smaller.
The technique was developed by Paul Butler of the Carnegie Institution of Washington and Geoffrey Marcy of the University of California at Berkeley. Butler and Marcy are in the midst of a long-term project to search each sun-like star in the Milky Way up to a distance of 150 light-years.
A light-year is the distance light travels in a year in a vacuum, about 5.88 trillion miles. The Milky Way is the home galaxy of our solar system and contains about 200 billion stars.
The findings will be published in an upcoming issue of Astrophysical Journal Letters under lead author Brad Carter of the University of Southern Queensland, Australia.
Before extrasolar planets were discovered, researchers assumed other solar systems would be similar to ours. However, only a handful of the planets discovered so far follows the nearly circular orbit of our solar system. Most extrasolar planets had elliptical orbits, and many orbit too close to their host star for the planetary system to be similar to our own.
Humberto Campins, a professor of astronomy and physics at University of Central Florida in Orlando, Florida, said the finding, if true, indicates that techniques for detecting planetary systems similar to our own are improving.
"We've been trying to find a planetary system like our solar system for a long time. If these people have found a Jupiter, then I'm delighted. Ideally, in the future we want to find planets like Earth capable of supporting life."