harps

HARPS, or High Accuracy Radial velocity Planet Searcher, is a high-precision optical spectrograph designed to detect exoplanets by measuring tiny variations in the radial velocity of stars caused by orbiting planets. It is mounted on the ESO 3.6-meter telescope at La Silla Observatory in Chile and is fed by optical fibers from the telescope. The instrument is housed in a vacuum-sealed, temperature-controlled environment to minimize instrumental drift. HARPS delivers high spectral resolving power (R ≈ 115,000) over a visible-wavelength range of about 378–691 nm and achieves radial-velocity precision around 1 meter per second for bright stars. Wavelength calibration uses a simultaneous reference technique, typically a thorium-argon lamp in a second fiber, which tracks instrumental drift and stabilizes measurements over long timescales.

Launched in the early 2000s, HARPS was developed by a collaboration led by the Geneva Observatory with support from ESO and partners. It quickly became one of the most successful planet-search instruments, contributing to the discovery and confirmation of many exoplanets, including several low-mass “super-Earth” planets and multi-planet systems, and to statistical studies of planet populations. The instrument has inspired subsequent high-precision spectrographs such as HARPS-N in the northern hemisphere and ESPRESSO on the Very Large Telescope, which aim for even higher precision.

As of the 2020s, HARPS remains in operation and continues to provide valuable radial-velocity data for exoplanet research, contributing to the expansion of known planetary systems and the understanding of planetary formation and dynamics.