Mayor and Queloz caught the first exoplanet in a star's 56 m/s wobble

In 1995 not a single planet was known around a sun-like star. The radial-velocity idea was old — watch the star's Doppler shift as an unseen planet tugs it around — but the signals are cruel: Jupiter moves our Sun at only about 12 m/s, and Mayor's first home-built spectrograph at the Haute-Provence Observatory in 1977 bottomed out near 300 m/s. Searches therefore targeted Jupiter analogs with decade-long orbits, requiring stability and patience nobody had.

Mayor's Geneva group rebuilt the whole chain: optical fibres carried starlight to the spectrograph undistorted, new CCDs raised sensitivity, custom software reduced the images. Doctoral student Didier Queloz pushed the velocity floor to 10–15 m/s by spring 1994 and sampled stars rapidly. Around 51 Pegasi the velocity swung with a 4.23-day period and ~56 m/s amplitude — a Jupiter-sized gas ball circling in days, where theory said giants could not form. They spent months ruling out pulsation and artefacts before announcing in October 1995; the planet was so peculiar nobody believed it.

The Nature paper of November 1995 has drawn over 3,000 citations and opened the class of 'hot Jupiters'. More than 4,000 exoplanets are now known, most in systems nothing like ours, forcing a rewrite of planet-formation theory around migration. The Nobel Prize in Physics 2019 went half to Mayor and Queloz for the discovery, and radial-velocity precision has kept climbing toward the 0.09 m/s tug of an Earth twin.

Sample fast; a close-in giant wobbles hardest

Doppler radial velocity is mass-weighted: tracking the star's motion was the only way to weigh what could not be seen.

The wobble amplitude grows as the period shrinks, so close-in giants shout while true Jupiter analogs whisper.

Fibre-fed, stabilized spectroscopy cut the noise floor from 300 m/s to 10–15 m/s — below the 56 m/s signal, which is the whole game.

High-cadence sampling over a few nights beats a decade of sparse monitoring when the orbit lasts 4.2 days.

Point the new instrument where the signal is strongest, not where the answer is expected: the first hot Jupiter was easy to see precisely because it was the planet theory said could not exist.

Hot Jupiters turned out to be common, and planetary migration entered every formation model. Kepler and TESS later found thousands more worlds by transit, but the radial-velocity method remains the way their masses are weighed. Mayor and Queloz shared the other half of the 2019 Nobel Prize in Physics with cosmologist James Peebles, and surveys now chase 0.1 m/s precision for true Earth analogs.