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For the first
time astronomers have worked out chemicals in the atmosphere of
a planet which orbits a distant star.
They used the
Hubble Space Telescope to look at a planet 150 light-years away
and found it has sodium in its atmosphere.
Scientists say
it is an important step because the technique might one day be used
to find evidence of extraterrestrial life.
The planet orbits
a star called HD 209458 in the constellation Pegasus. It is one
of 76 that have been found in orbit of distant stars, but is the
first to have its atmosphere chemically analysed.
The astronomers
knew that as the planet moved in front of its parent star light
would pass through the atmosphere on its way to the Earth.
They devised
a computer programme which could read changes in the light made
by the atmospheric chemicals.
Although this
experiment only looked for sodium it is now being tweaked to search
for Earth-like chemicals such as methane and water vapour.
David Charbonneau,
an astronomer at the California Institute of Technology, said: "Suddenly,
discussing searches for Earth-like planets seems quite reasonable.
"This opens
up an exciting new phase of extrasolar planet exploration, where
we can begin to compare and contrast the atmospheres of planets
around other stars."
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