Earth-like planet discovered outside solar system
ANNE MCILROY
From Wednesday's Globe and Mail
April 24, 2007 at 5:53 PM EST
A team of European astronomers has found a planet outside our solar system that is the most Earth-like ever discovered. Those who spotted it say it could be covered in water, a necessary ingredient for life.
The planet, detected using a telescope in Chile, has a mass about five times that of the Earth. It is 14 times closer to its star than the Earth is to the sun. But that star — Gliese 581 — is what is known as a red dwarf, and is smaller, colder and 50 times fainter than our sun.
This means the planet appears to lie in what astronomers call the Goldilocks zone — not too hot, not too cold for life that depends on water, rather than ice. A number of teams, including one in Canada, have been hunting for a planet that is capable of sustaining life, one that would change our view of the universe and mean that we are not alone.
The European team announced yesterday that they have found the best contender to date.
"We have estimated that the mean temperature of this super-Earth lies between zero and 40 degrees Celsius, and water would thus be liquid," says Stéphane Udry, the Geneva-based astronomer who is the lead author of a paper to be published as a letter to the editor in the journal Astronomy and Astrophysics.
"Moreover, 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 in oceans."
Gliese 581 is among the 100 closest stars to Earth, 20.5 light years away in the constellation Libra.
"Because of its temperature and relative proximity, this planet will most probably be a very important target for future space missions dedicated to the search for extraterrestrial life," says Xavier Delfosse, a member of the team that made the discovery and an astronomer at University of Grenoble in France.
"On the treasure map of the universe, one would be tempted to mark this planet with an X."
But that X lies well beyond reach of any current spaceship or unmanned probe, says Chris McCarthy, an astronomer at San Francisco State University.
"Let's just says it would take thousands of years to get there using current technology."
Jason Wright, at the University of California Berkeley, is another expert in exoplanets, or planets that orbit a star other than the sun.
He says it may be possible to find out more about this newly discovered planet using space-based telescopes.
"The closer a star is the easier it is to use a telescope to study its planets."
This isn't the first planet to be detected orbiting Gliese 581. Two years ago astronomers using the same 3.6-metre telescope at the European Southern Observatory in Chile found a much bigger planet. It was more the size of Neptune, with a mass 15 times that of the Earth.
This new planet is the smallest planet outside our solar system found up until now, the European astronomers say. It completes its orbit in 13 days.
They say they have also found signs of a third planet, one with a mass about eight times that of the Earth and an orbit that takes 84 days.
There are a number of different techniques to find planets orbiting other stars, and so far roughly 200 have been detected.
The European team looked for a star that was wobbling because of the gravitational pull exerted by an unseen planet. You can measure the size of the planet from the size of the wobble, Dr. McCarthy says.
He is one of the growing number of researchers looking for new planets, and potential worlds like our own, using both ground-based and space-based telescopes.
He says yesterday's announcement is big news.
But he cautions that more work needs to be done.
"It is still unclear what kind of planet this could be. It could be gaseous. It could be rocky. But the less massive it is the more likely it is to be rocky and thus similar to Earth.''
easynash
Islam, eminently logical, placing the greatest emphasis on knowledge, purports to understand God's creation:Aga Khan 4.
The God of the Quran is the One whose Ayats(Signs) are the Universe in which we live, move and have our being:Aga Khan 3
