The Pan-Pacific Planet Search: A Southern Hemisphere Search for Planets Orbiting Evolved Massive Stars

The vast majority of known extrasolar planets orbit stars with a narrow range of masses (0.7-1.3 M-circle dot). Little is known about the properties of planetary systems with host stars significantly more massive than the Sun. Planet formation models predict that giant planets are more common around higher-mass stars (M-* > 1.5M(circle dot)). However, these types of stars pose severe observational challenges while on the main sequence, resulting in a strong bias against them in current planet searches. Fortunately, it is possible to obtain high-precision Doppler velocities for these massive stars as they evolve off the main sequence and cool as sub-giants. We describe the Pan-Pacific Planet Search, a survey of 170 sub-giant stars using the 3.9m Australian Astronomical Telescope. In collaboration with J. Johnson's Keck survey of Northern "retired A stars", we are monitoring nearly every subgiant brighter than V = 8. This survey will provide critical statistics on the frequency and characteristics of planetary systems formed around higher-mass stars.