Kepler-22b: A 2.4 earth-radius planet in the habitable zone of a sun-like star

William J. Borucki, David G. Koch, Natalie Batalha, Stephen T. Bryson, Jason Rowe, Francois Fressin, Guillermo Torres, Douglas A. Caldwell, Jørgen Christensen-Dalsgaard, William D. Cochran, Edna Devore, Thomas N. Gautier, John C. Geary, Ronald Gilliland, Alan Gould, Steve B. Howell, Jon M. Jenkins, David W. Latham, Jack J. Lissauer, Geoffrey W. MarcyDimitar Sasselov, Alan Boss, David Charbonneau, David Ciardi, Lisa Kaltenegger, Laurance Doyle, Andrea K. Dupree, Eric B. Ford, Jonathan Fortney, Matthew J. Holman, Jason H. Steffen, Fergal Mullally, Martin Still, Jill Tarter, Sarah Ballard, Lars A. Buchhave, Josh Carter, Jessie L. Christiansen, Brice Olivier Demory, Jean Michel Désert, Courtney Dressing, Michael Endl, Daniel Fabrycky, Debra Fischer, Michael R. Haas, Christopher Henze, Elliott Horch, Andrew W. Howard, Howard Isaacson, Hans Kjeldsen, John Asher Johnson, Todd Klaus, Jeffery Kolodziejczak, Thomas Barclay, Jie Li, Søren Meibom, Andrej Prsa, Samuel N. Quinn, Elisa V. Quintana, Paul Robertson, William Sherry, Avi Shporer, Peter Tenenbaum, Susan E. Thompson, Joseph D. Twicken, Jeffrey Van Cleve, William F. Welsh, Sarbani Basu, William Chaplin, Andrea Miglio, Steven D. Kawaler, Torben Arentoft, Dennis Stello, Travis S. Metcalfe, Graham A. Verner, Christoffer Karoff, Mia Lundkvist, Mikkel N. Lund, Rasmus Handberg, Yvonne Elsworth, Saskia Hekker, Daniel Huber, Timothy R. Bedding, William Rapin

Research output: Contribution to journalArticlepeer-review

189 Scopus citations


A search of the time-series photometry from NASA's Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 0.060 M and 0.979 0.020 R. The depth of 492 10 ppm for the three observed transits yields a radius of 2.38 0.13 Re for the planet. The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion. A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits. The final validation of the planet is provided by 16 radial velocities (RVs) obtained with the High Resolution Echelle Spectrometer on Keck I over a one-year span. Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3σ upper limit of 124 M , safely in the regime of planetary masses, thus earning the designation Kepler-22b. The radiative equilibrium temperature is 262 K for a planet in Kepler-22b's orbit. Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the habitable zone of any star other than the Sun.

Original languageEnglish (US)
Article number120
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 1 2012

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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