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 hours 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 hours 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 = 0.895±0.060 M , and R = 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 −1.29 M ⊕ , R P = 1.416 +0.033 −0.036 R ⊕ , and ρ P = 8.8 +2.1 −2.9 g cm −3 . Kepler-10b is the smallest transiting exoplanet discovered to date.

SECURE MASS MEASUREMENTS FROM TRANSIT TIMING: 10 KEPLER EXOPLANETS BETWEEN 3 AND 8 M ⊕ WITH DIVERSE DENSITIES AND INCIDENT FLUXES

“…Radial velocity (RV)spectroscopy has provided the bulk of mass measurements of transiting exoplanets (Batalha et al 2011;Winn et al 2011;Fressin et al 2012;Gillon et al 2012;Gautier et al 2012;Howard et al 2013;Pepe et al 2013;Weiss et al 2013;Haywood et al 2014;Marcy et al 2014;Dressing et al 2015). However, among subNeptune-mass planets, RV mass detections are limited to planets on short orbital periods, because the RV signal depends on the strength of planet-star interactions and declines with orbital distance.…”

Front Matter: Volume 8152

“…The first unquestionably rocky planet was announced by the Kepler team in January of 2011. 38 Radial velocity observations of this planet indicated it has a mass of 4.5 M ⊕ , so with a radius of 1.4 R ⊕ this planet has a density of 8.8 g cm −3 . Asteroseismology provided a much improved radius estimate for Kepler-10b's star.…”

Mass-Radius Relationships of Rocky Exoplanets

“…Owing to the variable slope of mass-radius relations, planetary mean density in the giant-planet mass range is mainly constrained by precise radius determinations, whereas mass and radius pose equally important constraints on structural models of low-mass planets. Bruntt et al (2010); b) Batalha et al (2011); c) CHEOPS proposal (http://cheops.unibe.ch); d) PLATO M3 proposal (http://www.oact.inaf.it/plato/PPLC/Home.html).…”