What Fraction of Sun-like Stars have Planets?

Abstract

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 allow the most precise velocity measurements, ~25% possess planets. By identifying trends of the exoplanet mass and period distributions in a sub-sample 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 at least ~9% of Sun-like stars have planets in the mass and orbital period ranges Msin(i) > 0.3 M_Jupiter and P 0.1 M_Jupiter and P < 60 years. Even this larger area of the mass-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%.Comment: Conforms to version accepted by ApJ. Color version and movie available at http://bat.phys.unsw.edu.au/~charley/download/whatfrac