Earth-like planet found around star Gliese 581, 20.5 LYs away

The team includes Stephane Udry, of the Geneva Observatory in Switzerland, and Xavier Delfosse, of the Grenoble University in France. They used the HARPS (High Accuracy Radial velocity Planet Searchers) instrument on the European Southern Observatory (La Silla, Chile) to discover the planet.

The planet is about 1.5 times larger than the Earth and has about five times more mass than the Earth. Also, it is the first exoplanet (or extrasolar planet: a planet outside of the solar system) to be discovered that orbits its star within what is considered a habitable zone for the existence of liquid water.

The team thinks that the planet’s surface temperature is between 0 and 40 degrees Celsius (32 and 104 degrees Fahrenheit).

The star Gliese 581 is in the constellation Libra. It is one of one-hundred stars that are closest to the Earth. Its distance of 20.5 light-years (LYs) away makes it about 123 trillion miles (205 trillion kilometers) from the Earth. (One light-year is the distance that light travels in vacuum in one year—a distance of about 6 trillion miles, or 10 trillion kilometers.) In addition, the star is about one third the size of the Sun.

Also orbiting Gliese 581 is a larger planet, Gliese 581 b, which is about the size of the planet Neptune. It was discovered on November 30, 2005 by a team of Swiss and French astronomers. The planet Neptune, the eighth farthest planet from the Sun, is about 17 times more massive than the Earth.

Astronomers are also searching for a third planet about Gliese 581, which the European team think could be about eight times larger than the Earth.