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Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer (B.-O. Demory et al.)

Details: Published on 15 September 2011

Vol. 533
In section 10. Planets and planetary systems

Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer

by B.-O. Demory, M. Gillon, D. Deming, D. Valencia, S. Seager, B. Benneke, C. Lovis, P. Cubillos, J. Harrington, K. B. Stevenson, M. Mayor, F. Pepe, D. Queloz, D. Segransan, and S. Udry, A&A 533, A114

55 Cnc is a bright star (V=6, K=4) known to possess a system of at least five planets around it. One of these, 55 Cnc e, has an orbital period of only 17 hours and 40 minutes, the shortest of all known exoplanets. The planet was not known to transit, but two independent observations with space telescopes, MOST in the visible and Spitzer in the infrared, have shown that 55 Cnc e transits its star. Demory et al. present the analysis of the Spitzer observation and the measurement of the mass and radius of the planet, 7.8 Mearth and 2.1 Rearth, respectively. This result shows that 55 Cnc e is a relatively low-density planet that must contain a large fraction of its mass in volatiles, including water vapor. The question of the formation and dynamical evolution of this planet is still open. Its relation to the much denser rocky super-Earths CoRoT-7b and Kepler-10b is unclear.