Three "super Earth" planets have been found orbiting a nearby star at a distance where life in theory could exist, according to a record-breaking tally announced on Tuesday by the European Southern Observatory (ESO).
The three are part of a cluster of as many as seven planets that circle Gliese 667C, one of three stars located a relatively close 22 light years from Earth in the constellation of Scorpio, it said.
The planets orbit Gliese 667C in the so-called Goldilocks Zone -- a distance from the star at which the temperature is just right for water to exist in liquid form rather than being stripped away by stellar radiation or locked permanently in ice.
"It's exciting that we've found a nearby star that has so many planets in its habitable zone," said University of Washington astronomer Rory Barnes, part of an international team.
The planets are called "super Earths" because they are relatively small compared to the giants that comprise most of the exoplanets, which lie beyond our Solar System, spotted since 1995.
A handout photo provided by the European Southern Observatory (ESO) shows an artist’s impression of the view from the exoplanet Gliese 667Cd looking towards the planet’s parent star (Gliese 667C). In the background to the right, the more distant stars in this triple system (Gliese 667A and Gliese 667B) are visible and to the left in the sky one of the other planets, the newly discovered Gliese 667Ce, can be seen as a crescent. A record-breaking three planets in this system are super-Earths lying in the zone around the star where liquid water could exist, making them possible candidates for the presence of life. This is the first system found with a fully packed habitable zone. (AFP Photo/ESO/M. Kornmesser)
It is the first time that so many "super Earths" have been netted in one scientific haul, and shows the value of seeking out low-mass, Sun-like stars that appear to generate these promising worlds, the astronomers said.
Still unconfirmed is whether the trio are rocky planets, as opposed to gassy worlds where toxic or suffocating gases would make life impossible.
"These planets are good candidates to have a solid surface and maybe an atmosphere like the Earth's, not something like Jupiter's," Barnes said in a press release issued by his university.
Their close proximity "makes it like they are 'tidally locked,' which in this case means the same hemisphere always faces the star," he said. "Fortunately, we know that this state can still support life."
Even if these planets are a potential home from home, it would be impossible to reach them with the slow chemical rockets available today.
The three stars in the Gliese 667 system have excited intense interest among astronomers. The new finds were made by a consortium that pored over previous data and added new observations using ESO's hi-tech observatory and US Magellan telescopes in Chile and the W.M. Keck Observatory on Hawaii.