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Discovering the growth histories of exoplanets: the Saturn analog HD 149026b

Dodson-Robinson, Sarah E. and Bodenheimer, Peter (2009) Discovering the growth histories of exoplanets: the Saturn analog HD 149026b. Astrophysical Journal Letters, 695 (2). L159-L162. ISSN 2041-8205.

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The transiting "hot Saturn" HD 149026b, which has the highest mean density of any confirmed planet in the Neptune-Jupiter mass range, has challenged theories of planet formation since its discovery in 2005. Previous investigations could not explain the origin of the planet's 45-110 Earth-mass solid core without invoking catastrophes such as gas giant collisions or heavy planetesimal bombardment launched by neighboring planets. Here we show that HD 149026b's large core can be successfully explained by the standard core accretion theory of planet formation. The keys to our reconstruction of HD 149026b are (1) applying a model of the solar nebula to describe the protoplanet nursery, (2) placing the planet initially on a long-period orbit at Saturn's heliocentric distance of 9.5 AU, and (3) adjusting the solid mass in the HD 149026 disk to twice that of the solar nebula in accordance with the star's heavy element enrichment. We show that the planet's migration into its current orbit at 0.042 AU is consistent with our formation model. Our study of HD 149026b demonstrates that it is possible to discover the growth history of any planet with a well-defined core mass that orbits a solar-type star.

Item Type:Article
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Dodson-Robinson, Sarah E.0000-0002-8796-4974
Bodenheimer, Peter0000-0001-6093-3097
Additional Information:© 2009 American Astronomical Society. Print publication: Issue 2 (2009 April 20); received 2009 January 3; accepted for publication 2009 March 10; published 2009 March 30. Support for S.D.R’s work was provided by NASA through the Spitzer Space Telescope Fellowship Program. P.B. received support from the NASA Origins Grant NNX08AH82G. The authors thank Chas Beichman for helpful comments.
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Subject Keywords:methods: analytical; planetary systems: formation; planetary systems: protoplanetary disks; planets and satellites: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20090527-122915699
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14319
Deposited By: Jason Perez
Deposited On:18 Aug 2009 23:03
Last Modified:09 Mar 2020 13:18

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