Wed, Sep 01, 2004 - Page 7 News List

Planet found that could sustain life

`SUPER-EARTH' Astronomers have discovered several new planets in a week's time, with teams in the US and Europe competing in their hunt for new worlds

THE GUARDIAN , LONDONAND AP, NEW YORK

European scientists have found a planet circling a distant star that could be home to life.

The planet, the first detected so far that is enough like Earth for life to develop, orbits a star called mu Arae in the southern constellation Altar. The planet, which was spotted in June, is 14 times the mass of Earth and, like Earth, could be composed of rock and support an atmosphere. That sounds huge, but many of the previous exoplanets have been closer to the size of Jupiter, about 318 times the mass of Earth.

No planet beyond the solar system, known as exoplanets, has been seen by optical telescopes. But astronomers can infer the presence of a dark orbiting companion. Almost all 120 exoplanets discovered so far have been Jupiter-sized or bigger: gas giants far too big to support life.

But the planet that orbits mu Arae every 9.5 days lies at the threshold of the largest possible rocky planets. It has a temperature of more than 627?C, and its dimensions are on the scale of Neptune or Uranus.

This "super-Earth" appears to be orbiting between the star and a larger, previously known exoplanet, making it the first multiple planet system to be spotted beyond our own solar system.

The discovery, across a distance of 50 light years, was possible only because of the accuracy of an instrument called HARPS, a spectrograph on the European Southern Observatory's 3.6m telescope at La Silla in Chile.

With this tool, researchers can measure changes in the radial velocity of a star to an accuracy of 1m a second. Any such cyclical changes are evidence of the gravitational tug of an invisible companion.

Researchers had already detected one Jupiter-sized companion to mu Arae, and a closer look with their new instrument showed an additional planet.

Francois Bouchy, one of the observing team, said: "This new planet appears to be the smallest yet discovered around a star other than the sun. This makes mu Arae a very exciting planetary system."

Planet-hunting is becoming the hottest field in astronomy, with hundreds of researchers joining a race that just a decade ago was reserved for a few dreamers.

This past week has been a dizzying one with three teams in the US and Europe rushing to announce their discoveries of new exoplanets.

Yesterday, NASA was expected to cap the excitement with details on what the space agency describes as a "new class" of exoplanets found by one of the US teams, led by University of California-Berkeley astronomer Geoffrey Marcy.

"It's been a great week," said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, where scientists announced a competing discovery last week. "They have finally broken through to a new level."

Now many experts say it won't be long before astronomers detect planets that are similar to Earth's dimensions and characteristics -- perhaps even suitable for sustaining life with an oxygen-rich atmosphere and oceans.

NASA officials wouldn't discuss details of the latest findings on Monday.

The Harvard-Smithsonian center discovered a Jupiter-sized planet orbiting a star in the constellation Lyra 500 light years away. What makes the US discovery noteworthy is that it was found through a network of small telescopes.

In the next 20 years, NASA hopes to launch new space observatories to get a sharper view of exoplanets and perhaps find some that are more Earthlike. The first mission, known as the Kepler observatory, is scheduled to launch in 2007.

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