Discovery and Rossiter-McLaughlin effect of exoplanet Kepler-8b

Jon M. Jenkins, William J. Borucki, David G. Koch, Geoffrey W. Marcy, William D. Cochran, William F. Welsh, Gibor Basri, Natalie M. Batalha, Lars A. Buchhave, Timothy M. Brown, Douglas A. Caldwell, Edward W. Dunham, Michael Endl, Debra A. Fischer, Thomas N. Gautier, John C. Geary, Ronald L. Gilliland, Steve B. Howell, Howard Isaacson, John Asher JohnsonDavid W. Latham, Jack J. Lissauer, David G. Monet, Jason F. Rowe, Dimitar D. Sasselov, Andrew W. Howard, Phillip MacQueen, Jerome A. Orosz, Hema Chandrasekaran, Joseph D. Twicken, Stephen T. Bryson, Elisa V. Quintana, Bruce D. Clarke, Jie Li, Christopher Allen, Peter Tenenbaum, Hayley Wu, Søren Meibom, Todd C. Klaus, Christopher K. Middour, Miles T. Cote, Sean McCauliff, Forrest R. Girouard, Jay P. Gunter, Bill Wohler, Jennifer R. Hall, Khadeejah Ibrahim, A. K.M. Kamal Uddin, Michael S. Wu, Paresh A. Bhavsar, Jeffrey Van Cleve, David L. Pletcher, Jessie L. Dotson, Michael R. Haas

Research output: Contribution to journalArticlepeer-review

71 Scopus citations


We report on the discovery and the Rossiter-McLaughlin (R-M) effect of Kepler-8b, a transiting planet identified by the NASA Kepler Mission. Kepler photometry and Keck-HIRES radial velocities yield the radius and mass of the planet around this F8IV subgiant host star. The planet has a radius R P = 1.419 RJ and a mass MP = 0.60MJ, yielding a density of 0.26 gcm-3, one of the lowest planetary densities known. The orbital period is P = 3.523 days and the orbital semimajor axis is 0.0483+0.0006-0.0012 AU. The star has a large rotational vsini of 10.5 ± 0.7 kms-1 and is relatively faint (V ≈ 13.89 mag); both properties are deleterious to precise Doppler measurements. The velocities are indeed noisy, with scatter of 30 ms -1, but exhibit a period and phase that are consistent with those implied by transit photometry. We securely detect the R-M effect, confirming the planet's existence and establishing its orbit as prograde. We measure an inclination between the projected planetary orbital axis and the projected stellar rotation axis of λ = - 26°.4 ± 10°. 1, indicating a significant inclination of the planetary orbit. R-M measurements of a large sample of transiting planets from Kepler will provide a statistically robust measure of the true distribution of spin-orbit orientations for hot Jupiters around F and early G stars.

Original languageEnglish (US)
Pages (from-to)1108-1119
Number of pages12
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 1 2010

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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