What Fraction of Sun-like Stars Have Planets?

The radial velocities of 1800 nearby Sun-like stars are currently being monitored by eight high-sensitivity Doppler exoplanet surveys. Approximately 90 of these stars have been found to host exoplanets massive enough to be detectable. Thus, at least 5% of target stars possess planets. If we limit our analysis to target stars that have been monitored the longest ( 15 years), 11% possess planets. If we limit our analysis to stars monitored the longest and whose low surface activity allows the most precise velocity measurements, 25% possess planets. By identifying trends of the exoplanet mass and period distributions in a subsample of exoplanets less biased by selection effects and linearly extrapolating these trends into regions of parameter space that have not yet been completely sampled, we find that at least 9% of Sun-like stars have planets in the mass and orbital period rangesM sin i > 0:3MJup and P < 13 years and at least 22% have planets in the larger range M sin i > 0:1MJup and P < 60 years. Even this larger area of the log(mass)-log(period) plane is less than 20% of the area occupied by our planetary system, suggesting that this estimate is still a lower limit to the true fraction of Sun-like stars with planets, which may be as large as 100%. Subject heading: planetary systems On-line material: color figures