La mesure de la vitesse radiale d`une étoile repose sur l`effet

ELODIE:'un'instrument'pour'mesurer'la'vitesse'des'étoiles''
ELODIE:'an'instrument'to'measure'the'speed'of'stars''
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The!measurement!of!stellar!radial!velocity!is!based!on!the!Doppler-Fizeau!effect!that!connects!the!speed!of!a!
body! to! the! wavelengths! of! the! emi=ed! light.! Dispersing! the! light! of! a! star! with!a!spectrograph! permits! to!
iden?fy!the!spectral!absorp?on!lines!and!to!determine!their!Doppler!shi@!rela?ve!to!the!lines!measured!in!the!
laboratory.!
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In!the!60s,!Roger!Griffin!built!an!instrument!which!projected!the!stellar!spectrum!on!a!mask!consis?ng!of!a!nega?ve!spectrum!of!
the!star!Arcturus.!The!amount!of!light!passing!through!the!mask!is!measured!with!a!photomul?plier.!When!the!mask,!shi@ed!by!a!
micrometer!screw,!coincides!exactly!with!the!stellar!spectrum,!the!transmi=ed!light!is!then!at!a!minimum!and!the!posi?on!of!the!
mask!gives!the!velocity!of!the!star!rela?ve!to!Arcturus!with!an!accuracy!of!1!km/s.!In!1977,!using!the!same!principle,!a!french-
swiss!team!built!the!CORAVEL!instrument!that!was!installed!on!the!1-m!swiss!telescope!at!OHP.!
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!
The! ELODIE! spectrograph,! a.k.a.! super! Coravel,! was!developed! in! the! early! 90s! by! the! technical! staff! of! OHP! under! the! direc?on! of!
Philippe!Véron!and!in!collabora?on!with!André!Baranne!from!Marseille!Observatory!and!Michel!Mayor!from!Geneva!Observatory.!The!
instrument!was!connected!to!the!telescope!through!20-m!of!op?cal!fiber.!Its!op?cal!configura?on!with!an!echelle!gra?ng!and!a!cross!
disperser!allowed! to! register! on! a! CCD! camera! the! en?re!visible!spectrum.! Placed!in!an!air-condi?oned! room,! the! spectrograph! was!
fi=ed!with!a!double!protec?on!to!improve!its!thermal!stability.!
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!
The!first!spectrum!was!obtained!in!June!1993.!Thanks!to!ELODIE,!the!first!planet!orbi?ng!a!star!other!than!the!
Sun!was!discovered!by!Michel!Mayor!and!Didier!Queloz!in!1995!using!the!radial!velocity!measurements!of!the!
star!Peg!51!with!a!accuracy!of!10!m/s.!The!instrument!was!used!un?l!August!2006.!ELODIE!has!produced!over!
35000!spectra!and!remarkable!contribu?ons!in!exoplanetology!and!stellar!physics.!
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ELODIE!team!members!with!from!le@!to!right!:!!
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