High Accuracy Radial Velocity Planet Searcher

The High Accuracy Radial Velocity Planet Searcher (HARPS) is a spectrometer project that began observations in 2003. It is used to detect extrasolar planets by measuring a star's radial velocity—its speed toward or away from an observer. This is achieved by observing the Doppler effect on the star's spectral lines. A planet's gravitational pull causes a star to wobble, and HARPS can detect tiny shifts in radial velocity, as small as 30 cm per second. This sensitivity has allowed HARPS to discover numerous extrasolar planet candidates, including several "super-Earths". The HARPS project is a collaboration that includes astronomers from the University of Geneva and the University of Cambridge.123