The discovery of a Jupiter--mass planet in orbit around the solar--type star 51Peg has been reported by Michel Mayor and Didier Queloz (Geneva Observatory) on October 6th at the 9th Cambridge workshop on "cool stars, stellar systems, and the sun" held at Florence (Italy). The claim is based on 18 months of precise Doppler measurements done with the ELODIE spectrograph of the Observatoire de Haute-Provence (France). The parameters of the orbital motion are:

P=4.2293(+-0.0011) days
e=0 (fixed)
K=0.059(+-0.003) km/s
a1sini= 34(+-2)E+6 meter
f(m)=0.91(+-0.15)E-10 solar mass

Following this annoncement, confirmations of the 4.2d period radial velocity variation have been obtained at mid-October by a team at Lick Observatory, as well as by a joint team from the High Altitude Observatory and the Harvard-Smithsonian Center for Astrophysics.

Intensive photmetric monitoring has also be done at ESO (LA Silla Obs.) by G. Burki, M. Burnet and M. Kuenzli. They report that no evidence of eclipses can be seen. The r.m.s. of the magnitude (on 17 nights) is 0.037-Vmag, not different from two comparison stars. A 4.2d-period photometric variability larger than 0.002 can be ruled out.

M. Mayor, D. Queloz (Geneva Obs)
G. Marcy, P. Butler (SF State Univ., UC Berkeley)
R. Noyes, S.Horner (Harvard, Penn St.)
G. Burki, M. Burnet, M Kuenzli (Geneva Obs, Lausanne University)