Earthlike planet found

It's got the same climate as Earth, plus water and gravity. A newly
discovered planet is the most stunning evidence that life - just like us - might
be out there.

The discovery was announced today by a team of European astronomers, using a
telescope in La Silla in the Chilean Andes.

The Earth-like planet that could be covered in oceans and may support life is
20.5 light years away, and has the right temperature to allow liquid water on
its surface.

This remarkable discovery appears to confirm the suspicions of most astronomers
that the universe is swarming with Earth-like worlds.

We don't yet know much about this planet, but scientists believe that it may be
the best candidate so far for supporting extraterrestrial life.

The new planet, which orbits a small, red star called Gliese 581, is about
one-and-a-half times the diameter of the Earth.

It probably has a substantial atmosphere and may be covered with large amounts
of water - necessary for life to evolve - and, most importantly, temperatures
are very similar to those on our world.

It is the first exoplanet (a planet orbiting a star other than our own Sun) that
is anything like our Earth.

Of the 220 or so exoplanets found to date, most have either been too big, made
of gas rather than solid material, far too hot, or far too cold for life to
survive.

"On the treasure map of the Universe, one would be tempted to mark this planet
with an X," says Xavier Delfosse, one of the scientists who discovered the
planet.

"Because of its temperature and relative proximity, this planet will most
probably be a very important target of the future space missions dedicated to
the search for extraterrestrial life."

Gliese 581 is among the closest stars to us, just 20.5 light years away (about
120 trillion miles) in the constellation Libra. It is so dim it can be seen only
with a good telescope.

Gliese 581c is about 12,000 miles across (Earth is a little under 8,000
pole-to-pole).

It has a mass five times that of Earth, probably made of the same sort of rock
as makes up our world and with enough gravity to hold a substantial atmosphere.

Astrobiologists - scientists who study the possibility of alien life - refer to
a climate known as the Goldilocks Zone, where it is not so cold that water
freezes and not so hot that it boils, but where it can lie on the planet's
surface as a liquid.

In our solar system, only one planet - Earth -lies in the Goldilocks Zone. Venus
is far too hot and Mars is just too cold. This new planet lies bang in the
middle of the zone, with average surface temperatures estimated to be between
zero and 40c (32-102f). Lakes, rivers and even oceans are possible.

The surface gravity is probably around twice that of the Earth and the
atmosphere could be similar to ours.

Although the new planet is in itself very Earth-like, its solar system is about
as alien as could be imagined. The star at the centre - Gliese 581 - is small
and dim, only about a third the size of our Sun and about 50 times cooler.

The two other planets are huge, Neptune-sized worlds called Gliese 581b and d
(there is no "a", to avoid confusion with the star itself).

The Earth-like planet orbits its sun at a distance of only six million miles or
so (our Sun is 93 million miles away), travelling so fast that its "year" only
lasts 13 of our days.

The parent star would dominate the view from the surface - a huge red ball of
fire that must be a spectacular sight.

It is difficult to speculate what - if any - life there is on the planet. If
there is life there it would have to cope with the higher gravity and solar
radiation from its sun.

We do know its sun is an ancient star - in fact, it is one of the oldest stars
in the galaxy, and extremely stable. If there is life, it has had many billions
of years to evolve.

This makes this planet a prime target in the search for life. According to Seth
Shostak, of the Search for Extraterrestrial Intelligence Institute in
California, the Gliese system is now a prime target for a radio search. 'We had
actually looked at this system before but only for a few minutes. We heard
nothing, but now we must look again.'

By 2020 at least one space telescope should be in orbit, with the capability of
detecting signs of life on planets orbiting nearby stars. If oxygen or methane
(tell-tale biological gases) are found in Gliese 581c's atmosphere, this would
be good circumstantial evidence for life.

Dr Malcolm Fridlund, a European Space Agency scientist, said the discovery of
Gliese 581c was "an important step" on the road to finding life.

"If this is a rocky planet, it's very likely it will have liquid water on its
surface, which means there may also be life."

Interestingly, Gliese 581c is so close to the Earth that if its putative
inhabitants only had our level of technology, they could - just about - pick up
some of our radio signals, such as the most powerful military transmitters.
Quite what would happen if we for our part did receive a signal is unclear.

"There is a protocol, buried away in the United Nations," says Dr Shostak. "The
President would be told first, after the signal was confirmed by other
observatories. But we couldn't keep such a discovery secret."

It may be some time before we detect any such signals, but it is just possible
that today we are closer than ever to finding life in the stars.

Click here to see picture 1

Click here to see picture 2

Click here to see picture 3

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