A Trio Of Super-Earths

♥ On 16th June, at an International Conference, a team of European Astronomers announced a new discover considered as a remarkable breakthrough in the field of extra-solar planets.
Using the HARPS Spectrograph (High Accuracy Radial Velocity Planet Searcher) of the 3.6-m telescope at the ESO La Silla Observatory, the Astronomers have found a triple system of Super-Earths around the Star HD 40307. However, looking at their entire sample studied with HARPS, the astronomers count a total of 45 candidate planets with a mass below 30 Earth masses and an orbital period shorter than 50 days. This implies that one solar-like star out of three harbours such planets.

“Since the discovery in 1995 of a planet around the star 51 Pegasi by Mayor and Didier Queloz, more than 270 exoplanets have been found, mostly around solar-like stars. Most of these planets are giants, such as Jupiter or Saturn, and current statistics show that about 1 out of 14 stars harbours this kind of planet.”

According with Stéphane Udry, one of Mayor's colleagues, “With the advent of much more precise instruments such as the HARPS spectrograph on ESO's 3.6-m telescope at La Silla, the Astronomers can now discover smaller planets, with masses between 2 and 10 times the Earth's mass," as that planets are more massive than the Earth but less massive than Uranus and Neptune (about 15 Earth masses), they are called Super-Earths.

“The group of astronomers have now discovered a system of three Super-Earths around a rather normal star, which is slightly less massive than our Sun, and is located 42 light-years away towards the southern Doradus and Pictor constellations.”

Mayor’s also says that it was "made very precise measurements of the velocity of the star HD 40307 over the last five years, which clearly reveal the presence of three planets".

The planets, having 4.2, 6.7, and 9.4 times the mass of the Earth, orbit the star with periods of 4.3, 9.6, and 20.4 days, respectively.

These discoveries have been announced on 16 June at the international conference "Extra-solar Super-Earths" which took place in Nantes, France, on 16 to 18 June.

Further Info.:
http://www.eso.org/public/outreach/press-rel/pr-2008/pr-19-08.html