2011ApJ...729...27B

NASA's Kepler Mission uses transit photometry to determine the frequency of Earth-size planets in or near the habitable zone of Sun-like stars. The mission reached a milestone toward meeting that goal: the discovery of its first rocky planet, Kepler-10b. Two distinct sets of transit events were detected: (1) a 152±4 ppm dimming lasting 1.811±0.024 hr with ephemeris T [BJD] =2454964.57375^+0.00060_–0.00082+ N*0.837495^+0.000004_–0.000005 days and (2) a 376±9 ppm dimming lasting 6.86±0.07 hr with ephemeris T [BJD] =2454971.6761^+0.0020_–0.0023+ N*45.29485^+0.00065_–0.00076 days. Statistical tests on the photometric and pixel flux time series established the viability of the planet candidates triggering ground-based follow-up observations. Forty precision Doppler measurements were used to confirm that the short-period transit event is due to a planetary companion. The parent star is bright enough for asteroseismic analysis. Photometry was collected at 1 minute cadence for >4 months from which we detected 19 distinct pulsation frequencies. Modeling the frequencies resulted in precise knowledge of the fundamental stellar properties. Kepler-10 is a relatively old (11.9±4.5 Gyr) but otherwise Sun-like main-sequence star with T_eff= 5627±44 K, M_{sstarf} = 0.895±0.060 M_☉, and R_{sstarf}= 1.056±0.021 R_☉. Physical models simultaneously fit to the transit light curves and the precision Doppler measurements yielded tight constraints on the properties of Kepler-10b that speak to its rocky composition: M_P= 4.56^+1.17_–1.29M_⊕, R_P= 1.416^+0.033_–0.036R_⊕, and ρ_P= 8.8^+2.1_–2.9 g/cm3. Kepler-10b is the smallest transiting exoplanet discovered to date.