'Super-Earth' planet spurs hope for billions more SPACE

An artist's conception of the alien planet GJ 667Cc, which is located in the habitable zone of its parent star. An artist's conception of the alien planet GJ 667Cc, which is located in the habitable zone of its parent star. Photo: Carnegie Institution For Science Photo: Carnegie Institution For Science Image 1 of / 1 Caption Close 'Super-Earth' planet spurs hope for billions more 1 / 1 Back to Gallery

Astronomers have detected a rocky "super-Earth" planet orbiting a nearby star in a region where life could possibly exist, a finding that led one of the team from UC Santa Cruz to predict there must be billions more of them in the Milky Way.

The newfound planet is big, at least 4 1/2 times as massive as Earth. It is 22 light-years from Earth, orbits its star every 28 days, and lies in the star's "habitable zone," where temperatures are just right - neither too hot nor too cold - for liquid water to support life on its surface.

Astronomers like to call that "the Goldilocks zone."

The planet's sun is a member of a curious triple-star group, involving two suns that are "binaries" orbiting each other, and a third that is possibly hosting two or three additional planets. One of them could be a "gas giant" similar to Jupiter, and the other could be another "super-Earth," with a 75-day orbit, the astronomers said.

"Detecting this planet so near implies that our galaxy must be teeming with billions of potentially habitable rocky planets," said Steven Vogt, a veteran UC Santa Cruz planet hunter who is a member of the discovery team and is now completing a new telescope called the Automated Planet Finder at the Lick Observatory atop Mount Hamilton near San Jose.

Leaders of the discovery team are Paul Butler and Guillem Anglada-Escudé of the Carnegie Institution for Science in Washington, D.C., and astronomers from Germany, England, Australia and Chile.

Less that two years ago, Vogt and Butler led another team that discovered the first of these "exoplanets" - planets orbiting stars beyond our solar system - in a habitable zone around a star called Gliese 581, about 20.5 light-years from Earth.

This new one is just about as near, but its star has no official name, just GJ 667 in the star catalogs.

The team detected the new planet by measuring tiny wobbles in GJ 667's motion across the sky caused by the tug of the planet's gravity. The star itself is known as an M-class dwarf - one of the most common types in the Milky Way, and "was expected to be a rather unlikely star to host planets," Vogt said.

But the fact that such a common type of star does host them leads astronomers to believe there must be countless more undetected exoplanets in the Milky Way, he said.

"This planet is the new best candidate to support liquid water and, perhaps, life as we know it," Anglada-Escudé said.

The team's findings appear online and will be published in Astrophysical Journal Letters, a leading journal for exoplanet discoveries.

Altogether, 755 exoplanets have been confirmed since the first one was detected in 1995, according to the Extrasolar Planet Encyclopaedia, maintained by astronomers at the Paris Observatory.