- One in 20 stars in the night sky could be orbited by
Earth-like planets capable of supporting alien life, according to a new
British study.
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- Astronomers have shown that rocky planets lying in a
habitable zone where temperatures are suitable for life are more common
than was previously thought.
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- Within 10 years, telescopes should be powerful enough
to detect these planets directly and reveal whether their atmospheres contain
tell-tale traces of life, they say.
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- Since the mid-1990s, astronomers have discovered 105
planetary systems outside our Solar System.
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- These far distant planets cannot be seen with telescopes,
but they can be indirectly detected. If planets are big enough and close
enough to a star, their gravitational pull causes the star to wobble slightly
- a motion that can be detected from Earth.
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- Ever since the first "extrasolar" planetary
system was detected in the mid-1990s, scientists have been eager to find
out whether they could harbour life. For life as we know it to exist, a
rocky planet would need to lie within a region known as the Goldilocks
- where temperatures are not too hot, nor too cold, for life.
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- Prof Barrie Jones of the Open University told the Royal
Astronomical Society's conference in Milton Keynes: "All we have discovered
so far are Jupiter-type planets which are not likely to harbour life. But
we expect there to be smaller rocky worlds within the habitable zone where
the water would be liquid."
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- His team created computer models of nine of the known
solar systems. Prof Jones launched virtual rocky planets with masses between
one tenth and 10 times the size of the Earth into the models to see what
would happen. The team launched the planets into different parts of the
Golilocks zone - with each orbit taking four or five days to process on
a personal computer.
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- In some systems, the habitable planets were ejected from
their orbit by the immense gravitational tug of the giant planets. But
in around half, there were either safe zones within the Goldilocks zone,
or the entire zone was safe.
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- The models also show that life could develop in about
two thirds of the systems because the habitable zone moves outwards over
time as the star becomes more active.
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- "We now think that at least 10 per cent of stars
in the Earth's backyard have planetary systems," he said. "If
only half of these are able to sustain a rocky planet in the habitable
zone, it means that one in 20 could harbour life. It is possible that the
universe is teeming with life."
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