Kepler 's First Rocky Planet: Kepler-10b

Abstract

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(-0.00082)(+0.00060) + N * 0.837495(-0.000005)(+0.000004) days and (2) a 376 +/- 9 ppm dimming lasting 6.86 +/- 0.07 hr with ephemeris T [BJD] = 2454971.6761(-0.0023)(+0.0020) + N * 45.29485(-0.00076)(+0.00065) 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-star = 0.895 +/- 0.060M(circle dot), and R-star = 1.056 +/- 0.021R(circle dot). 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(-1.29)(+1.17) M-circle plus, R-P = 1.416(-0.036)(+0.033) R-circle plus, and rho P = 8.8(-2.9)(+2.1) g cm(-3). Kepler-10b is the smallest transiting exoplanet discovered to date.