A Possible Origin for Giant Planets Found at Small Stellar Distances

Abstract

aps other ices) to provide enough mass to allow growth of the core before dissipation of the gas. High temperatures within a few astronomical units (AU) of the Sun would preclude such an origin. Jupiter, at 5.2 AU, is widely believed to have formed near the boundary of ice condensation in the solar nebula (7). In contrast, as of this writing six planets are known with masses comparable to Jupiter and orbits well inside 1 AU; these are companions of the stars 51 Peg, t Boo, Ups And, 55 Cnc, HD114762, and 70 Vir. The first three all have semimajor axes a 0.05 AU, the next has a 0.1 AU, and the last two are at 0.4 and 0.47 AU. In addition, a planet of 47 UMa is at a distance of 2.1 AU. Lin et al. (5) suggested that giant planets migrated inward while tidally linked to an evolving circumstellar disk that was accreting onto the star. This mechanism implies that planets must have formed simultaneously with the star itself, bu