In the news this month... another impressive exoplanet haul from HARPS
Artists impression of the Earth-like planet Gliese 667 C discovered by HARPS CREDIT: ESO/L. Calçada
2009 has been a good year for exoplanets, and one team of astronomers have discovered most of them. Since the first planet was found orbiting a star other than the Sun, many more have been discovered using increasingly sensitive instruments and sophisticated techniques. Because they are so faint compared to their parent stars, most planets are discovered through indirect methods. One of the most successful has been the radial velocity method which uses the principle of the Doppler effect to detect the tiny changes in velocity of a star caused by an orbiting planet.
This is the technique used by the High Accuracy Radial Velocity Planet Searcher, or HARPS, instrument, mounted on the European Southern Observatory's 3.6-m telescope at La Silla in Chile which repeatedly measures the radial velocities of stars that might host planetary systems. On the 19th of October, members of the HARPS team presented their latest results: the discovery of another 32 new planets, bringing the total number of known exoplanets to more than 400. The radial velocity technique is most sensitive to large planets orbiting close to their parent star, but due to its high precision HARPS is capable of detecting smaller planets known as super-Earths. The new batch of exoplanets range in size from just five times the mass of the Earth to up to 10 times the mass of Jupiter.
HARPS has been largely responsible for the detection of 24 of the 28 known planets with masses below 20 times that of Earth and has now discovered more than 75 of the 400 known exoplanets, making it the most productive current planet finder. However, HARPS will soon have competition in the form of Kepler, a NASA satellite launched in March with the aim of detecting Earth-sized planets in the habitable zone, the region around a star where water can exist as a liquid. Rather than measuring the wobble of stars, Kepler will monitor their brightness looking for the tiny dips in intensity caused by planetary transits.
Mayor, M.; Pepe, F.; Queloz, D.; Bouchy, F.; Rupprecht, G.; Lo Curto, G.; Avila, G.; Benz, W.; Bertaux, J.-L.; Bonfils, X.; dall, Th.; Dekker, H.; Delabre, B.; Eckert, W.; Fleury, M.; Gilliotte, A.; Gojak, D.; Guzman, J. C.; Kohler, D.; Lizon, J.-L.; Long (2003). Setting New Standards with HARPS Messenger (114), 20-24 Other: 2003Msngr.114...20M