http://www.timesonline.co.uk/tol/news/science/article5739563.ece
'trillions' of planets could be supporting life
Almost every star similar to the Sun probably has a life-harbouring planet like the Earth in orbit around it, a leading astronomer said yesterday.
The discovery of hundreds of planets around distant stars in our galaxy suggests that most solar systems have a world like ours that is capable of supporting life, and many of them are likely to have evolved it, according to Alan Boss, of the Carnegie Institution in Washington.
Nasa’s Kepler spacecraft, which will be launched next month to seek Earth-like worlds, is expected to find thousands of rocky planets in the patch of sky it surveys, Dr Boss told the American Association for the Advancement of Science conference in Chicago.
“We’re on the verge of finding out convincingly how frequently habitable planets occur in the Universe,” he said. “A little over 20 years ago we knew of no other planetary system other than our own.
We now know of well over 300. I suspect that virtually every star when you look up at the night sky has an Earth-like planet around it.” These “exoplanets” are mainly gas giants like Jupiter, but they do include some “super-Earths” that are a few times larger than our planet. While smaller worlds like ours are invisible to existing telescopes, Kepler will be capable of finding them.
“The estimates are that super-Earths probably occur in one third of solar-like stars, and I would say that those oddball planets are the tip of the iceberg,” Dr Boss said. “About three or four years from now there’ll be a press conference announcing how frequently Earths occur. It’s quite an exciting time to be alive.”
His expectation was that 85 per cent of Sun-like stars had one Earth-like planet, and that some could have many more. Given that there are 100 billion Sun-like stars in the galaxy, and 100 billion galaxies in the Universe,
there may be 10 billion trillion planets that are good candidates for life. That is a one followed by 22 noughts. (noughts is another word for zero's)
With a habitable world sitting for five or ten billion years around another star, it was inevitable that some sort of life would form, Dr Boss said. If you had a planet with the right temperature and water for billions of years, you were bound to get life. Comets carrying the organic building blocks of life regularly bombard planets, he said.
If Kepler, and a European planet-finder called Corot, do find Earth-like worlds, the next step will be to launch space-based telescopes to study them. “If we find the signature of oxygen, that would be pretty strong proof that not only are they habitable, but they are inhabited,” Dr Boss said.
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It was likely that some planets had produced intelligent organisms and civilisations, though our chances of locating one were very remote, Dr Boss said. “Maybe we haven’t found them yet because we haven’t looked long and hard enough in the galaxy, and maybe there are intelligent civilisations which could have formed and lasted 100,000 years, but maybe they happened 100 million years ago, and so we’re just out of phase with them.”
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