Abstract
We examine the late stages of terrestrial planet formation around each star in the α Centauri A and α Centauri B binary system. Each integration begins with a "bimodal" mass distribution of 14 large embryos embedded in a disk of smaller planetesimals orbiting one of the stars. These initial conditions were chosen because when they are used in simulations about a single star with giant planets, they lead to systems most closely resembling our solar system. However, it is far from certain that such a planetesimal distribution actually occurs either in single or binary star systems. We follow the evolution of the accreting bodies at various values of the inclination of the midplane of the disk relative to the binary orbit for 200 Myr to 1 Gyr. In simulations in which the midplane of the disk was inclined ≤30° relative to the binary orbital plane, three to five terrestrial planets were formed around α Cen A. When the embryos in the disk were moving retrograde relative to the binary plane, four or five terrestrial planets formed. From two to five planets formed in a disk centered around α Cen B, with α Cen A perturbing the system in the same plane. The aforementioned resulting terrestrial planetary systems are quite similar to those produced by calculations of terrestrial planet growth in the Sun-Jupiter or Sun-Jupiter-Saturn systems. In contrast, terrestrial planet growth around a star lacking both stellar and giant planet companions is slower and extends to larger semimajor axis for the same initial disk of planetary embryos. In systems with the accreting disk initially inclined at 45° relative to the binary star orbit, two to five planets formed despite the fact that more than half of the disk mass was perturbed into the central star. When the disk was inclined at 60° to the binary plane, the stability of the planetary embryos decreased dramatically because of larger variations in eccentricity caused by the Kozai resonance, and almost all of the planetary embryos and planetesimals were lost from these systems.