High Accuracy Radial Velocity Planet Searcher

The HARPS can attain a precision of 0.97 m/s (3.5 km/h),^[2] making it one of only two instruments worldwide with such accuracy.^{[citation needed]} This is due to a design in which the target star and a reference spectrum from a thorium lamp are observed simultaneously using two identical optic fibre feeds, and to careful attention to mechanical stability: the instrument sits in a vacuum vessel which is temperature-controlled to within 0.01 kelvins.^[3] The precision and sensitivity of the instrument is such that it incidentally produced the best available measurement of the thorium spectrum.^{[citation needed]} Planet-detection is in some cases limited by the seismic pulsations of the star observed rather than by limitations of the instrument.^[4]

The principal investigator on the HARPS is Michel Mayor who, along with Didier Queloz and Stéphane Udry, have used the instrument to characterize the Gliese 581 planetary system, home to one of the smallest known exoplanets orbiting a normal star, and two super-Earths whose orbits lie in the star's habitable zone.^[5]

It was initially used for a survey of one-thousand stars.^{[citation needed]}

Since October 2012 the HARPS spectrograph has the precision to detect a new category of planets: habitable super-Earths. This sensitivity was expected from simulations of stellar intrinsic signals, and actual observations of planetary systems. Currently, the HARPS can detect habitable super-Earth only around low-mass stars as these are more affected by gravitational tug from planets and have habitable zones close to the host star.^[6]

This is an incomplete list of exoplanets discovered by the HARPS. The list is sorted by the date of the discovery's announcement. As of December 2017, the list contains 134 exoplanets.

• 
  HELIOS instrument installed to feed sunlight via fibre optics to the HARPS^[7]
• 
  A decade of discoveries from HARPS^[8]
• 
  HARPS spectrograph
• 
  HARPS spectrograph detail
• Animation of HD 10180 with its seven planets

Similar instruments:

• HARPS-N is a copy of this instrument installed in the northern hemisphere in 2012.
• HARPS3 is an updated design of this instrument that will be installed on an upgraded and roboticised Isaac Newton Telescope, in 2024.
• Fiber-optic Improved Next-generation Doppler Search for Exo-Earths, operating at Lick observatory since 2009
• Anglo-Australian Planet Search or AAPS is another southern hemisphere planet search program.
• ESPRESSO is a new-generation spectrograph for ESO's VLT.
• Automated Planet Finder, at the Lick observatory, commissioned in 2013.
• CAFE (Calar Alto Fibre-fed Echelle spectrograph) installed on the Calar Alto Observatory's 2.2-metre telescope in 2014, and the CARMENES mounted on the 3.5-metre telescope in 2016.
• EXPRES is a third generation radial velocity spectrograph that is planned to be installed on the Lowell Discovery Telescope.

Space based detectors :

• CoRoT, spacecraft operating since 2007
• Kepler, operational until 2018
• Terrestrial Planet Finder, cancelled
• Space Interferometry Mission, construction halted in 2010
• Darwin, early studies for a multi-satellite mission

• Media related to HARPS spectrograph at Wikimedia Commons
• "HARPS Home Page". ESO. Retrieved 25 April 2009.
• "The Exoplanet Hunter HARPS: unequalled accuracy and perspectives towards 1 cm/s precision" (PDF). ESO. (Contains list of discoveries from 2005 survey.)
• "New Planet-Hunting Technology Accelerates Discovery of Exo-Planets & Solar Systems". Daily Galaxy. 17 June 2008. Archived from the original on 7 October 2008. Retrieved 19 October 2008.
• "Astronomers discover 4 new planets". NASA. 27 March 2007. Archived from the original on 22 April 2007.