Earth-Like Planet Discovered in Libra

NPR--Space

Earth-Like Planet Discovered in Libra

by Nell Boyce

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Astronomers have discovered the most Earth-like planet yet in another solar system. It is the first planet outside of our solar system that could be home to liquid water. Above is an artist's illustration of the planet, which scientists think is either rocky, or covered with oceans. ESO

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The Earth-like planet orbits Gliese 581 — a red dwarf located 20.5 light-years away in the constellation Libra. Red dwarf stars are too faint to be seen from Earth with the naked eye. Digital Sky Survey

Morning Edition, April 25, 2007 · Scientists have discovered a new planet in the constellation Libra. The small, rocky planet is special because it appears to have mild temperatures, like Earth. Researchers believe it looks like the first planet outside of our solar system that could be home to liquid water, and maybe even life.

Our solar system has only eight planets — nine if you count Pluto. But outside of our solar system, around other stars, scientists have found dozens and dozens of planets.

"We have discovered more than 100 planets, here in Geneva," says Michel Mayor, a planet hunter at the University of Geneva.

Almost all of these known "extrasolar" planets are giant balls of gas, much like Jupiter or Saturn. Such massive planets are relatively easy to find. They have a gravitational pull that makes their stars wobble, and when scientists see that wobble, they know there is a planet. Small, rocky planets cause less of a wobble, making them harder to find.

Still, Mayor and his colleagues have had some luck using the European Southern Observatory's big telescope at La Silla, Chile. They recently pointed it at a nearby star called Gliese 581, in the constellation Libra.

"It's one of our closest neighbors in the galaxy," Mayor says.

His team has found three planets around this star, and one of them is particularly interesting. They think the planet is a little bigger than Earth, with about five times the Earth's mass. It orbits very close to its star, going all the way around in just 13 days. The planet isn't super hot though, because Gliese 581 is a red dwarf, which is much dimmer and cooler than our sun.

Scientists calculate that average temperatures on the surface of the planet should be around 32 to 104 degrees Fahrenheit. Mayor says that is a friendly environment for liquid water and maybe even life.

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