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Published May 20, 2013 | Accepted Version + Published
Journal Article Open

Mass-Radius Relationships for Very Low Mass Gaseous Planets

Abstract

Recently, the Kepler spacecraft has detected a sizable aggregate of objects, characterized by giant-planet-like radii and modest levels of stellar irradiation. With the exception of a handful of objects, the physical nature, and specifically the average densities, of these bodies remain unknown. Here, we propose that the detected giant planet radii may partially belong to planets somewhat less massive than Uranus and Neptune. Accordingly, in this work, we seek to identify a physically sound upper limit to planetary radii at low masses and moderate equilibrium temperatures. As a guiding example, we analyze the interior structure of the Neptune-mass planet Kepler-30d and show that it is acutely deficient in heavy elements, especially compared with its solar system counterparts. Subsequently, we perform numerical simulations of planetary thermal evolution and in agreement with previous studies, show that generally, 10-20 M_⊕, multi-billion year old planets, composed of high density cores and extended H/He envelopes can have radii that firmly reside in the giant planet range. We subject our results to stability criteria based on extreme ultraviolet radiation, as well as Roche-lobe overflow driven mass-loss and construct mass-radius relationships for the considered objects. We conclude by discussing observational avenues that may be used to confirm or repudiate the existence of putative low mass, gas-dominated planets.

Additional Information

© 2013 The American Astronomical Society. Received 2013 January 15; accepted 2013 April 17; published 2013 May 3. We thank Tristan Guillot, Geoff Blake, Ruth Murray-Clay, Adam Burrows, and David Kipping for numerous useful conversations. We are grateful to the referee for a careful and insightful report that has greatly increased the quality of the manuscript. K.B. acknowledges the generous support from the ITC Prize Postdoctoral Fellowship at the Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics.

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Published - 2041-8205_769_1_L9.pdf

Accepted Version - 1304.5157.pdf

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August 22, 2023
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