HARP finds new planets

Physics Today : Thirty-two new planets have been discovered using the High Accuracy Radial Velocity Planet Searcher (HARPS), attached to the European Southern Observatory’s 3.6-meter telescope at La Silla, Chile.The findings, presented at a conference in Porto, Portugal , raise the number of known so-called exoplanets to more than 400, of which HARPS has discovered 75.HARPS has facilitated the discovery of 24 of the 28 planets known with masses below 20 Earth masses. As with the previously detected super-Earths, most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system.HARPS, which was installed in 2003, measures small changes in a star’s radial velocity—as small as 3.5 km/hour. The radial velocity fluctuates under the gravitational pull of an unseen exoplanet.HARPS has already discovered the first super-Earth ( around µ Ara ); the trio of Neptune-sized planets around HD 69830 ; Gliese 581d, the first super-Earth in the habitable zone of a small star; and earlier this year, the lightest exoplanet so far detected around a normal star, Gliese 581e . More recently, they found a potentially lava-covered world , with density similar to that of Earth’s."These observations have given astronomers a great insight into the diversity of planetary systems and help us understand how they can form,” says HARPS team member Nuno Santos.The team found three candidate exoplanets around stars that are metal-deficient. Such stars were originally thought to be less favorable for the formation of planets, which form in the metal-rich disk around the young star.However, now that planets up to several Jupiter masses have been found orbiting metal-deficient stars, planet formation models will have to be revised. Related press release 32 new exoplanets found