Scattering Outcomes of Close-in Planets: Constraints on Planet Migration
Abstract
Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large number of orbit integrations in systems with two and three gas-giant planets in close-in orbits (0.05 AU < a < 0.15 AU). We find that at these orbital separations, unstable systems starting with low eccentricities and mutual inclinations (e <~ 0.1, i <~ 0.1) generally lead to planet-planet collisions in which the collision product is a planet on a low-eccentricity, low-inclination orbit. This result is inconsistent with the observations. We conclude that eccentricity and inclination excitation from planet-planet scattering must precede migration of planets into short-period orbits. This result constrains theories of planet migration: the semi-major axis must shrink by 1-2 orders of magnitude without damping the eccentricity and inclination.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2014
- DOI:
- 10.1088/0004-637X/786/2/101
- arXiv:
- arXiv:1401.4457
- Bibcode:
- 2014ApJ...786..101P
- Keywords:
-
- planetary systems;
- planets and satellites: dynamical evolution and stability;
- planets and satellites: formation;
- planets and satellites: gaseous planets;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 11 pages, 3 figures, accepted for publication in ApJ