Galaxy loaded with billions of Earth-like planets

Our galaxy may be loaded with billions, possibly trillions, of Earth-like planets each of which would possibly be supporting Extra Terrestrial life, a leading US astronomer said yesterday. Dr Alan Boss of the Carnegie Institution of Science said many of these worlds could be inhabited by simple life forms. He was speaking at the annual meeting of the American Association for the Advancement of Science in Chicago.

Dr Boss also said we could even find the first one in the next four years. More than 300 new planets beyond our solar system have been found in recent years and researchers think it is only a matter of time before a habitable world is discovered.

"There are something like a few dozen solar-type stars within something like 30 light years of the Sun, and I would think that a good number of those, perhaps half of them, would have Earth-like planets," Boss says.

Dr Boss estimates that each Sun-like star probably has a planet like Earth which is capable of supporting life. He said: "I think that most likely the nearby 'Earths' are going to be inhabited with things which are perhaps more common to what Earth was like three or four billion years ago."

Boss said Nasa's Kepler mission, which is due to be launched in March, should begin finding some of the Earth-like planets within the next few years.

"About three or four years from now there'll be a press conference announcing just how frequently Earths occur. It's quite an exciting time to be alive," Dr Boss said. He also said he expected that as many as 85 per cent of Sun-like stars had at least one Earth-like planet, and some of them may have many more.

There are 100 billion Sun-like stars in the galaxy, and 100 billion galaxies in the Universe, so if he is right there may be 10 billion trillion planets that are good candidates for life. Life will have evolved on some of these worlds, Dr Boss said. "If you have a habitable world sitting around for four, five, ten billion years around another star, it's inevitable that some sort of life is going to form. It's like running an experiment with your refrigerator turned off: eventually things are going to grow in there.

The Kepler spacecraft, built by Boulder's Ball Aerospace, will search for these "other Earths" and will launch next month. The craft will the Earth company in its journey around the sun, and for three years will stare steadily at a single, hand-sized star field. It will study more than 100,000 sun-like stars that astronomers believe may have captured habitable planets in their gravitational fields.

If Kepler, and a European planet-finder called Corot, do find Earth-like worlds as expected, the next step will be to launch a new generation of space-based telescopes to study them in more detail. "We need to directly image these Earths and get light from the atmospheres, and if we find the signature of oxygen, that would be pretty strong proof that not only are they habitable, but they are inhabited," Boss added.

"Within about three or four years, there will be a press conference at Nasa headquarters and they will tell us just how frequently Earth-like planets occur and once we know that we will know how to take the next steps in the search for habitable planets," Boss said.