[meteorite-list] Scientists find most Earth-like planet yet

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Tue, 24 Apr 2007 22:44:54 -0500
Message-ID: <cjjt23l4an4niujgen7a87v5cnhesjmtfj_at_4ax.com>


WASHINGTON (Reuters) -- European astronomers have spotted what they say is the
most Earth-like planet yet outside our solar system, with balmy temperatures
that could support water and, potentially, life.

They have not directly seen the planet, orbiting a red dwarf star called Gliese
581. But measurements of the star suggest that a planet not much larger than the
Earth is pulling on it, the researchers say in a letter to the editor of the
journal Astronomy and Astrophysics.

"This one is the first one that is at the same time probably rocky, with water,
and in a zone close to the star where the water could exist in liquid form,"
said Stephane Udry of the Geneva Observatory in Switzerland, who led the study.

"We have estimated that the mean temperature of this super-Earth lies between 0
and 40 degrees Celsius, and water would thus be liquid."

Most of the 200 or so planets that have been spotted outside this solar system
have been gas giants like Jupiter. But this one is small.

"Its radius should be only 1.5 times the Earth's radius, and models predict that
the planet should be either rocky, like our Earth, or covered with oceans," Udry
said in a telephone interview.

It appears to have a mass five times that of Earth's.

The research team includes scientists credited with the first widely accepted
discovery of a planet outside our solar system, in 1995.

Many teams are looking for planets circling other stars. They are especially
looking for those similar to our own, planets that could support life.

That means finding water.

X marks the spot
"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 extra-terrestrial life," Xavier Delfosse, a member of the team
from Grenoble University in France, said in a statement.

"On the treasure map of the universe, one would be tempted to mark this planet
with an X."

Gliese 581 is among the 100 closest stars to Earth, just 20.5 light-years away
in the constellation Libra.

A light-year is the distance light travels in a year, about 6 trillion miles (10
trillion km).

It is smaller and dimmer than the sun, so the planet can be close to it and yet
not be overheated.

"These low-mass stars are the ones where we are going to be able to discover
planets in the habitable zone first," said planet-hunter David Bennett of the
University of Notre Dame in Indiana, who was not involved in the research.

Bennett cautioned that current temperature alone does not mean water still
exists on the planet. It could have burned off ages ago, when the star was
hotter than it is now.

Udry's team uses a method known as radial velocity, using the European Southern
Observatory telescope at La Silla, Chile.

The same team has identified one larger planet orbiting Gliese 581 already and
say they have strong evidence of a third planet with a mass about eight times
that of the Earth.

Future missions, perhaps in 20 to 30 years, may be able to block the light from
the star and take a spectrographic image of the planets. The color of the light
coming from the planet can give hints of whether water, or perhaps large amounts
of plant life, exist there.
Received on Tue 24 Apr 2007 11:44:54 PM PDT

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