Measurement of the Spin-Orbit Alignment in the Exoplanetary System HD 189733

Creators: Winn, Joshua N.; Johnson, John Asher; Marcy, Geoffrey W.; Butler, R. Paul; Vogt, Steven S.; Henry, Gregory W.; Roussanova, Anna; Holman, Matthew J.; Enya, Keigo; Narita, Norio; Suto, Yasushi; Turner, Edwin L.

Abstract

We present spectroscopy of a transit of the exoplanet HD 189733b. By modeling the Rossiter-McLaughlin effect (the anomalous Doppler shift due to the partial eclipse of the rotating stellar surface), we find the angle between the sky projections of the stellar spin axis and orbit normal to be λ = -1°.4 ± 1°.1. This is the third case of a "hot Jupiter" for which λ has been measured. In all three cases λ is small, ruling out random orientations with 99.96% confidence, and suggesting that the inward migration of hot Jupiters generally preserves spin-orbit alignment.

Additional Information

© 2006 American Astronomical Society. Received 2006 September 15; accepted 2006 November 1; published 2006 November 30. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. We thank Debra Fischer for running SME on our spectra and Scott Gaudi for very helpful discussions. We recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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