Skip to main content
eScholarship
Open Access Publications from the University of California

Observed Properties of Exoplanets: Masses, Orbits, and Metallicities

  • Author(s): Marcy, Geoffrey
  • et al.
Abstract

We review the observed properties of exoplanets found by the Doppler technique that has revealed 152 planets to date. We focus on the ongoing 18-year survey of 1330 FGKM type stars at Lick, Keck, and the Anglo-Australian Telescopes that offers both uniform Doppler precision (3 m/s) and long duration. The 104 planets detected in this survey have minimum masses (Msini) as low as 6 Earth-masses, orbiting between 0.02 and 6 AU. The core-accretion model of planet formation is supported by four observations: 1) The mass distribution rises toward the lowest detectable masses, dN/dM \propto 1/M. 2) Stellar metallicity correlates strongly with the presence of planets. 3) One planet (1.3 Saturn Masses) has a massive rocky core, M = 70 Earth-masses. 4) A super-Earth of about 7 Earth-masses has been discovered. The distribution of semi-major axes rises from 0.3 -- 3.0 AU (dN/dloga) and extrapolation suggests that about12% of the FGK stars harbor gas-giant exoplanets within 20 AU. The median orbital eccentricity is =0.25, and even planets beyond 3 AU reside in eccentric orbits, suggesting that the circular orbits in our Solar System are unusual. The occurrence ``hot Jupiters'' within 0.1 AU of FGK stars is 1.2%. Among stars with one planet, 14% have at least one additional planet, occasionally locked in resonances. Kepler and COROT will measure the occurrence of earth-sized planets. The Space Interferometry Mission (SIM) will detect planets with masses as low as 3 Earth-masses orbiting within 2 AU of stars within 10 pc, and it will measure masses, orbits, and multiplicity. The candidate rocky planets will be amenable to follow-up spectroscopy by the ``Terrestrial Planet Finder'' and Darwin.

Many UC-authored scholarly publications are freely available on this site because of the UC Academic Senate's Open Access Policy. Let us know how this access is important for you.

Main Content
Current View