Extrasolar Planets Detected by the Doppler TechniqueTo appear in the proceedings of the Workshop on BrownDwarfs and Extrasolar Planets held in Tenerife , 1997 ; ASP Conference Series

Precise Doppler measurements (< 15 m s ?1) of main sequence stars have revealed eight to date that exhibit Keplerian velocity variations consistent with planetary companions. The implied orbital periods range from 3.3-1100 d, the semimajor axes range from 0.04-2.2 AU, and the companion masses range from 0.45-6.8 M JUP /sin i. This mass range corresponds to the \giant planet" structures modeled by Burrows et al. (1995, 1997). The mass distribution of the planets peaks below 5 M JUP. Variations in the shapes of the absorption lines of 51 Peg reported by Gray (1997) are considered carefully, pending connrmation. Photometry and Doppler measurements of the four 51 Peg{like stars constrain the characteristics of the supposed stellar oscillations as follows: 1. No photometric periodicities are found: mag < 0.4 millimag. 2. Fluid motion (from integrating Vdt) would have to be 0.03 R. 3. Doppler variations exhibit a delta function in frequency for 51 Peg: No other harmonics or \modes" exist. 4. The oscillation periods do not correlate with stellar mass or metalicity. The detection of planets orbiting nearby Solar-type stars is now routinely possible by precise measurements of the Doppler shifts of the stellar spectra. The Sun serves as a benchmark in several respects. It exhibits an instantaneous velocity of 12.5 m s ?1 relative to the Solar System barycenter, due to the gravitational perturbations from Jupiter. The remaining planets and moons cause Solar reeex motions of only a few m s ?1 total. The Sun exhibits intrinsic Doppler stability in the integrated full{disk spectrum, with variations of less than 4 m s ?1 (McMillan et al. 1993, but see Deming & Plymate 1994), which implies that planets will be detectable for similar stars. Among the 60 F,G, and K-type dwarfs observed regularly at Lick Observatory, 80% exhibit rms velocity variations less than 10 m s ?1 , and the remainder show variations consistent with Keplerian motion 1