Washington: For the first time astronomers have discovered a planet outside our solar system that is potentially habitable, with Earth-like temperatures, a find researchers described Tuesday as a big step in the search for ''life in the universe.''
The planet is just the right size, might have water in liquid form, and in galactic terms is relatively nearby at 120 trillion miles (193 trillion km) away. But the star it closely orbits, known as a ''red dwarf,'' is much smaller, dimmer and cooler than our sun.
European astronomers 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.
"We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius (32 to 104 degrees F), and water would thus be liquid."
''Liquid water is critical to life as we know it,'' co-author Xavier Delfosse of Grenoble University in France, said in a statement. ''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. On the treasure map of the Universe, one would be tempted to mark this planet with an X.''
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.
About the planet
Earth-like planet, orbiting a red dwarf star
Appears to have a mass five times that of Earth's
Among the 100 closest stars to Earth
20.5 light-years away in the constellation Libra
Important for future space missions
Estimated temperature between 0 and 40 degrees Celsius
Water could exist in liquid form
Place to search for extra-terrestrial life
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