WASHINGTON Astronomers and amateur stargazers have used an unusual technique to find a solar system that closely resembles our own and say it may be a new and more productive way to scour the universe for planets -- and life.
They said technique, called microlensing, shows promise for finding many more stars, perhaps with Earthlike planets orbiting them.
"We found a solar system that looks like a scaled-down analog of our solar system," Scott Gaudi of Ohio State University, who led the study, told reporters.
The new solar system, described in Friday's issue of the journal Science, has two planets of similar size and orbit to Jupiter and Saturn. It is the first time microlensing has been used to find two planets orbiting a single star.
The star is smaller, dimmer and fainter than our sun and the two planets are less massive than Jupiter and Saturn, but orbit at distances similar to the distances that Jupiter and Saturn orbit our own sun. "So it looks like a scale model of our solar system," Gaudi said.
The planets were detected orbiting a star, called OGLE-2006-BLG-109L, 5,000 light-years away from Earth. A light-year is the distance light travels in a year, or about 6 trillion miles.
The team of astronomers from 11 countries used a technique called microlensing to spot the planets.
"Microlensing works by using the gravity of the star and the planet to bend and focus light rays from a star behind it," Gaudi said. "If you are looking at one star and another passes in the foreground (gravity from the front star) will focus and bend light rays. That causes the background star to be magnified," he added.
Any planets orbiting the star cause "a little bump" in this magnification effect, Gaudi said. In this case, the light from the more distant star was magnified 500 times.
Most of the other 250 or so extrasolar planets that have been seen have been detected using radio velocity -- tiny shifts in radiation, including light, that are caused by the Doppler effect. Most planets detected this way are super-large, super gassy and orbit very close to their suns.
"Microlensing is more sensitive to these cold, distant planets than the radiovelocity method," Gaudi said.
The discovery suggests these planets are common, the researchers said.
"Is there an Earth there in this system? For all we know there could be rocky planets in there but we couldn't find them," Gaudi said. "This could be a true solar system analog."
The 80-odd members of the Optical Gravitational Lensing Experiment worked frantically night after night during the 11-day period from late March through early April 2006 when the two stars were close enough to one another, as viewed from Earth, to cause the microlensing effect.
"We tried to get 24/7 coverage of the event," said Andrew Gould, professor of astronomy at Ohio State University. "It gets to be dawn in one place and we have to get somebody observing in another place."
They included professionals but also two amateurs -- one using a public telescope in Auckland, New Zealand, and Jenny McCormick, whose backyard telescope is listed as Farm Cove Observatory in Auckland, New Zealand, in the report.
"I work from home in our home-built observatory," McCormick told reporters. "It is quite useful. It is very easy to get on collecting data, cooking dinner and ironing clothes."