Cool Stars 14 - Submitted Abstract # 210
This version created on 05 October 2006

The Mass-Radius Relation for Low-Mass Exoplanets


Sara Seager, Carnegie Institution of Washington
Catherine Hier-Majumder, Carnegie Institution of Washington
Marc Kuchner, NASA/Goddard Space Flight Center

We present new mass-radius relationships for low-mass exoplanets with
masses from 0.l to 100  Earth masses.  We discuss how well
exoplanetary bulk composition can be determined, considering the
limiting observational error bars on transiting exoplanet masses and
radii.  We consider iron-type planets like Mercury, silicate-type
planets like Earth, and water worlds predominantly composed of water
ice.  We find a universal mass-radius relation for solid planets (with
masses less than 100  Earth masses), resulting from the similarity of
the equations of state of solid materials.  This universal mass-radius
relation allows an estimate of planetary bulk composition without
detailed calculations.

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