Tuesday, Jun 12, 2012, 10:24 AM -10:36 AM
Small Planets Do Not Require A Metal-Rich Environment
David W. Latham
, L. A. Buchhave
Niels Bohr Institute, University of Copenhagen, Denmark.
The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a fossil record of the chemical composition of the initial protoplanetary disc. Metal-rich stars are much more likely to harbor gas giant planets, thereby supporting the core accretion scenario of planet formation. However, whether the exoplanet-metallicity relationship extends into the terrestrial planet regime is unknown, but important for a better understanding of planet-formation processes. The unprecedented photometric sensitivity of the Kepler mission provides the first opportunity to probe the metallicities of a statistically significant number of stars hosting small planets. Here we report spectroscopic metallicities of the host stars of 226 exoplanet candidates discovered by Kepler. We find that, contrary to gas giants, the detection of small planets does not depend as strongly on the metallicity of the host star: Planets smaller than 4 Earth radii form around host stars with a wide range of metallicities.
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