Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone

Abstract

Main TextKepler is a NASA Discovery-class mission designed to determine the frequency of Earth-radius planets in and near the HZ of solar-like stars (1-6). Planets are detected as "transits" that cause the host star to appear periodically fainter when the planets pass in front it along the observer's line of sight. Kepler-62 (KIC 9002278, KOI 701) is one of approximately 170,000 stars observed by the Kepler spacecraft. Based on an analysis of long-cadence photometric observations from Kepler taken in Quarters 1 through 12 (May 13, 2009 through March 28, 2012, we report the detection of five planets including two super-Earth-size planets in the HZ and a hot Mars-size planet orbiting Kepler-62 ( Fig. 1 and Table 1). Prior to validation, three of these objects were designated as planetary candidates 701.02, and 701.03 in the Kepler 2011 catalog (7) and the Kepler 2012 catalog (8). KOI-701.04 and 701.05 were identified subsequently using a larger data sample (9).Analysis of high-resolution spectra indicates that Kepler-62 is a K2V spectral type with an estimated mass and radius (in solar units) of 0.69 ± 0.02 Mʘ and 0.63 ± 0.02 Rʘ (9). Examination of the sky close to Kepler-62 showed the presence of only one additional star that contributed as much as 1% to the total flux (figs. S3-S4)(9). Warm-Spitzer observations ( fig. S9) and the analysis of centroid motion (Table S1) were consistent with the target star as the source of the transit signals ( Fig. 1 and fig. S1). We computed the radius, semi-major axis, and radiative equilibrium 3 temperature of each planet (Table 1) based on light curve modeling given the derived stellar parameters (Table S3). Fig. 1. Kepler-62 light curves after the data were detrended to remove the stellar variability. Composite of phase-folded transit light curves (dots), data binned in ½ hour intervals (blue error bars), and model fits (colored curves) for Kepler-62b through -62f. Model parameters are provided in Table 1. The error bars get larger as the period becomes larger because there are fewer points to bin together. For the shortest periods, the bars are too small to see. Notes: 1) T 0 is the epoch in mid-transit in Barycentric Julian Days, P is the period, duration is the transit duration, "depth" is the percent reduction of the flux during the transits determined from the model fit to the data, R p /R * is the ratio of the radius of the planet to the radius of the star, a/R * is the ratio of the planet's semi-major axis to the stellar radius, b is the impact parameter in units of stellar radius, i is the orbital inclination, ecosω is the product of the orbital eccentricity e with the cosine of the periapse angle ω, a is the semi-major axis, and R p is the radius of the planet, and Maximum Mass is the upper limit to the mass based on transiting timing and RV observations, M⊕ is the mass of the Earth, and Teq is the radiative equilibrium temperature.2) The values of the uncertainties are ±1 standard deviation unless otherwise noted.3) Values for the maximum mass are for the 95 th p...

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