Discovery of planet increases chances of extraterrestrial life

Astronomers have detected a second planet orbiting a star that could be at the centre of a solar system similar to ours.

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Starquakes offer clues to alien life

Astronomers have detected a second planet orbiting a star that could be at the centre of a solar system similar to ours.

The discovery is yet more evidence that there may be many Earth-like planets in the Milky Way galaxy where extraterrestrial life could exist.

Already scientists have found more than 70 "exoplanets" outside our solar system. The latest recruit is about the size of Jupiter, the biggest of the nine planets orbiting the Sun.

The planet, which has not yet been named, is orbiting the star 47 Ursae Majoris in the Big Bear constellation some 50 light years away. The new planet is about three-quarters of the mass of Jupiter and orbits at a distance from its star that would take it between the orbits of Mars and Jupiter if it was in the solar system.

Scientists had previously found another planet, which was twice the size of Jupiter, to be in a circular orbit around the same star. A second planet suggests further planets may also exist.

One of the researchers, Debra Fischer of the University of California at Berkeley, said the latest planet brings astronomers closer to finding a distant solar system similar to our own. "For the first time we have detected two planets in nearly circular orbits around the same star. Most of the 70 planets people have found to date are in bizarre solar systems, with short periods and eccentric orbits close to the star.

"As our sensitivity improves we are finally seeing planets with longer orbital periods, planetary systems that look like our solar system," she said.

A team of astronomers from Washington's Carnegie Institution and Nasa made the discovery using two telescopes at the University of California's Lick Observatory. They detected the planet by measuring regular changes in the Doppler shift of starlight, which signals when the gravity of a planet is periodically pulling the star towards and away from the Earth.