Tiny exoplanet orbits cool star
One of the smallest planets ever found in another solar system has been discovered by astronomers at the European Southern Observatory in northern Chile.
A team of French and Swiss astronomers say they detected the small exoplanet orbiting the star Gl 581 in the Libra constellation, 20.5 light-years away from Earth.
G1 581 is a red dwarf, a small, cool, faint star that is the most common type in our galaxy.
While the star has a mass of only one-third of the Sun, the exoplanet is roughly as large as Neptune, which is 17 times larger than Earth.
Since 80 of the 100 stars closest to the Sun are red dwarfs, astronomers are interested in discovering if they have planets orbiting them.
"Our finding possibly means that planets are rather frequent around the smallest stars," says Dr Xavier Delfosse of the Grenoble Astrophysics Laboratory in France.
"It certainly tells us that red dwarfs are ideal targets for the search for exoplanets," says Delfosse.
The discovery was made using the HARPS spectrograph at the European Southern Observatory, located at La Silla, about 400 kilometres north of Santiago.
Of some 200 red dwarf stars studied, only two have been shown to have exoplanets in their orbits.
The new planet discovered at the Chile facility is one of the six smallest of 170 exoplanets detected by astronomers.
It travels in an orbit 6 million kilometres away from the star, and takes 5.4 days to complete its orbit.
By comparison, Mercury, the closest planet to the Sun in our own solar system, is 58 million kilometres from the Sun and takes 88 days for one revolution.
That close to its host star, the exoplanet is probably extremely hot, around 150°C the obervatory says.
The European Southern Observatory is sponsored by scientific institutions in 11 European countries.