Scientists find a 'super Earth.' Could it host life?

The newly discovered planet is five times Earth's mass and circles its sun every 13 days.

By Peter N. Spotts | Staff writer of The Christian Science Monitor

from the April 25, 2007 edition

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The quest to find Earth-like planets around other stars appears to have taken a significant step forward. Astronomers in Europe have detected a "super Earth" orbiting a dwarf star 20.5 light-years away.

The planet appears to be the most Earth-like of any of the more than 200 planets yet found outside the solar system.

Among these, only a handful of "super Earths" – a moniker for planets weighing in at two to 10 times Earth's mass – have been discovered so far. But to some astronomers, they may hold special significance. In theory, at least, they have the potential to be better platforms for the emergence of life than Earth itself.

The newly discovered planet's diameter is about 50 percent bigger than Earth's and tips the scales at five times Earth's mass, according to the team of scientists, which announced their findings Tuesday. Most intriguingly, it orbits its parent star at the right distance to allow for the possibility that liquid water has pooled and remains stable on its surface.

"The planet should be either rocky ... or covered with oceans" based on modeling studies, notes Stephane Udry, a researcher at the Geneva Observatory and head of the team reporting the results. Its findings are going through peer review for the journal Astronomy & Astrophysics.

To be sure, no water has yet been detected. Indeed, the planet itself has only been observed indirectly – through a slight wobble its gravitational tug imparts to the spectrum of Gliese 581, a star in the constellation Libra.

But researchers say the characteristics they can tease from that wobble point to a rocky planet orbiting once every 12.9 Earth days at a distance of about 6.5 million miles from the star.

If Gliese 581 were as big and hot as our sun, that would spell trouble. The solar system's innermost planet, Mercury, is nearly six times farther away from the sun and it's still a barren hunk of crackling hot rock on the daylight side and a frosty ice box on the night side. The sun's habitable zone is said to begin about 88 million miles from the star and drop off some 155 million miles out (think Earth to Mars).

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