EAS Publications Series

Research Article

A Survey of Multiple Planet Systems

Extrasolar Planets in Multi-Body Systems: Theory and Observations, Extrasolar Planets in M ulti-Body Systems, Toruń, Poland.

J. T. Wright

525 Davey Lab, Astronomy and Astrophysics, Eberly College of Science, The Pennsylvania State University, University Park, PA 16802, USA


To date, over 30 multiple exoplanet systems are known, and 28% of stars with planets show significant evidence of a second companion. I briefly review these 30 systems individually, broadly grouping them into five categories: 1) systems with 3 or more giant (M sin i> 0.2 MJup) planets, 2) systems with two giant planets in mean motion resonance (MMR), 3) systems with two giant planets not in MMR but whose dynamical evolution is affected by planet-planet interactions, 4) highly hierarchical systems, having two giant planets with very large period ratios (>30:1), and 5) systems of “Super-Earths”, containing only planets with (M sin i< 20 M). 
It now appears that eccentricities are not markedly higher among planets in known multiple planet systems, and that planets with M sin i<MJup have lower eccentricities than more massive planets. The distribution of semimajor axes for planets in multi-planet systems does not show the 3-day pile-up or the 1 AU “jump” of the apparently-single planet distribution.

(Online publication April 19 2010)