Les recherches de Stéphane Udry concernaient initialement la dynamique des galaxies. Aujourd'hui, son travail se concentre sur la recherche d'exoplanètes par la technique des vitesses radiales. Parmi ses découvertes, on peut notamment citer Gliese 581 c, planète qui, lors de l'annonce de sa découverte le , était celle présentant les caractéristiques les plus favorables à l'habitabilité parmi toutes les planètes connues. La planète fut découverte par l'analyse des données du spectrographe HARPS situé sur le télescope de 3,6 mètres de l'ESO à l'observatoire de La Silla au Chili.
Un nouvel instrument en construction à l'observatoire de Genève, appelé ESPRESSO (Echelle Spectrography for Rocky Exoplanet- and Stable Spectroscopic Observations), permettra selon Stéphane Udry de découvrir des planètes similaires à la Terre entre 2015 et 2020[1]
↑Joel Achenbach, « Newly found 'exoplanets' are out of this world », Washington Post, (lire en ligne, consulté le ) :
« Astronomer Stéphane Udry of Geneva University said by e-mail that a new instrument under development, known as ESPRESSO (Echelle Spectrograph for Rocky Exoplanet- and Stable Spectroscopic Observations), "should allow us to detect Earth twins around solar-type stars, within 5 to 10 years." "Personally, I am convinced that planets are everywhere," Udry said. "Nature does not like void." »
↑(en) Dennis Overbye, « 20 light years away, the most Earthlike planet yet », The New York Times, (lire en ligne, consulté le ) - « The most enticing property yet found outside our solar system is about 20 light years away in the constellation Libra, according to a team of European astronomers. The astronomers said Tuesday that they had discovered a planet five times as massive as the Earth orbiting a dim red star known as Gliese 581. It is the smallest of the 200 or so planets that are known to exist outside of our solar system, the extrasolar, or exo-, planets. It orbits its home star within the so-called habitable zone where surface water, the staff of life, could exist if other conditions are right, said Stéphane Udry of the Geneva Observatory. »
↑(en) John Noble Wilford, « Another Cousin to Jupiter Is Found », The New York Times, (lire en ligne, consulté le ) - « Dr. Stéphane Udry, a member of the team from the Geneva Observatory in Switzerland, said in an interview that what was missing in this planetary system — mammoth planets extremely close to the host stars — made it a more promising solar system analog than the one announced last week by the leading team of American planet hunters. The star the Americans found is accompanied by one and probably two Jupiter-size planets at closer distances than Mercury is from the Sun. »
↑(en) Jeremy Manier, « Just like home, yet light years from Earth », Chicago Tribune, (lire en ligne, consulté le ) - « As with nearly all such planetary discoveries, astronomers could not observe Gliese 581 directly because it is invisible in the glare of its sun. Instead, the European group led by Stephane Udry and Michael Mayor calculated the planet's presence from its tiny gravitational tug on the star. »
