RV searches with high-resolution spectrographs: From CORAVEL to ESPRESSO

Since the discovery in 1995 of 51 Peg b, radial velocity searches have proven to be one of the most effective ways of finding new extrasolar planets, in particular extrasolar planets orbiting nearby stars, where transits are often not detected. Back when the first exoplanet orbiting a Sun-like star was discovered, it was possible to detect the presence of a Jupiter-like planet in a close orbit to its star. Today, high-precision radial velocity measurements, obtained using high-resolution spectrographs, allow us to find Earth-mass planets that orbit inside, or close to, the habitable zone of their host stars. In some cases, with new-generation instruments such as ESPRESSO, it is possible to detect the presence of planets much lighter than the Earth. There was a time in which it was impossible to detect the presence of exoplanets by measuring radial velocity variations. There was a time in which it was expected that large stellar activity variations (assumed to be of the order of 20 m/s for quiet stars) could prevent us from detecting low-mass exoplanets. Increasingly more precise instrumentation and the advancement of the analysis techniques radically changed the situation and opened the door to the complete characterization of the low-mass exoplanetary population of the solar vicinity. Here, will embark in a short journey on the history of the radial velocity technique as a mean to detect extrasolar planets. From the early concept of spectrographs dedicated to the measurement of stellar velocities, to the detection of a planet with 1/4 the mass of the Earth orbiting Proxima Centauri.