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Published May 1, 2007 | Published
Journal Article Open

Direct measurement of the radius and density of the transiting exoplanet HD 189733B with the Chara array


We have measured the angular diameter of the transiting extrasolar planet host star HD 189733 using the CHARA optical/IR interferometric array. Combining our new angular diameter of 0.377 +/- 0.024 mas with the Hipparcos parallax leads to a linear radius for the host star of 0.779 +/- 0.052 R☉and a radius for the planet of 1.19 +/- 0.08 RJup. Adopting the mass of the planet as derived by its discoverers, we derive a mean density of the planet of 0.91 +/- 0.18 g cm^-3. This is the first determination of the diameter of an extrasolar planet through purely direct means.

Additional Information

© 2007. The American Astronomical Society. Received 2007 February 23; accepted 2007 April 20; published 2007 May 9. We would like to thank Andy Boden for sharing his SED fit tools with us, which we used to produce the fits seen in Figures 1 and 3, and we appreciate the care that CHARA Array operator P. J. Goldfinger used in obtaining many of these observations. The CHARA Array is funded by the National Science Foundation through NSF grants AST-0307562 and AST-06006958 and by Georgia State University through the College of Arts and Sciences and the Office of the Vice President for Research. Observations with PTI are made possible through the efforts of the PTI Collaboration, which we acknowledge. Funding for PTI was provided to the Jet Propulsion Laboratory under its TOPS (Towards Other Planetary Systems), ASEPS (Astronomical Studies of Extrasolar Planetary Systems), and Origins programs and from the JPL Director's Discretionary Fund. Part of the work described in this Letter was performed at the Jet Propulsion Laboratory under contract with the National Aeronautics and Space Administration. This research has made use of the SIMBAD literature database, operated at CDS, Strasbourg, France, and of NASA's Astrophysics Data System. This publication makes use of data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

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