April 6, 2008

Astronomers Discover Solar System Similar to Our Own

British astronomers have discovered a solar system similar to ours, with two planets that closely match Saturn and Jupiter orbiting a star about half the size of the Sun.

The finding suggests that systems like ours could be more common that previously thought, according to Martin Dominik of St Andrews University, who added that astronomers were on the brink of discovering many more such systems. 

Dr Dominik presented his work at the Royal Astronomical Society's National Astronomy Meeting in Belfast, and said the newly discovered planetary system, and others like it, could host terrestrial planets like Earth.   

"We found a system with two planets that take the roles of Jupiter and Saturn in our Solar System. These two planets have a similar mass ratio and similar orbital radius and a similar orbital period," Dr Dominik told BBC News.

"It looks like this may have formed in a similar way to our Solar System. And if this is the case, it looks like [our] Solar System cannot be unique in the Universe. There should be other similar systems out there which could host terrestrial planets."

Located about five thousand light years away, the newfound planetary system orbits the star OGLE-2006-BLG-109L, and is more compact than our own.

Nearly 300 extrasolar planets have been identified, but astronomers have consistently failed to find any systems similar to ours.   In fact, only 10% of the systems discovered so far are known to host more than one planet, Dr Dominik said.

But current techniques to find exoplanets were predisposed towards detecting giant gas planets orbiting at short distances from their parent stars, whereas the OGLE planets were found using a technique called gravitational micro-lensing, in which light from faraway planets is bent and magnified by the gravity of another star.

"It's a kind of scaled-down version of our Solar System. The star the planets are orbiting is half as massive as the Sun and they orbit half as distant to their host star as Jupiter and Saturn orbit around the Sun," said Dr Dominik.

Technological improvements will make it possible for exoplanet researchers to achieve their ultimate goal of finding habitable Earth-like and Mars-like planets, Dr Dominik said.

"I think it will happen quite soon," he said.  "Micro-lensing can already go below Earth mass and it has detected more massive planets in the habitable zone. So in the next few years, we will see something really exciting."

Dr Dominik spoke of competition between astronomers using micro-lensing and those who prefer the transit technique, which detects new planets as they pass in front of a parent star blocking a tiny fraction of the star's light, causing the star to periodically dim.

However, there was little chance to detect Earth-like worlds in OGLE-2006-BLG-109L as the system was too distant for current techniques to resolve planets the size of Earth, he added.


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