Kepler-16: A Transiting Circumbinary Planet Doyle, Laurance R.; Carter, Joshua A.; Fabrycky, Daniel C. ...
Science (American Association for the Advancement of Science),
09/2011, Letnik:
333, Številka:
6049
Journal Article
Recenzirano
We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses ...of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.
We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These ...results are based on the 1235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 R. For all planets with orbital periods less than 50 days, we measure occurrence of 0.130 + or - 0.008, 0.023 + or - 0.003, and 0.013 + or - 0.002 planets per star for planets with radii 2-4, 4-8, and 8-32 R, in agreement with Doppler surveys. We fit occurrence as a function of P to a power-law model with an exponential cutoff below a critical period Psub 0. For smaller planets, Psub 0 has larger values, suggesting that the "parking distance" for migrating planets moves outward with decreasing planet size.
About one-third of the ~1200 transiting planet candidates detected in the first four months of Kepler data are members of multiple candidate systems. There are 115 target stars with two candidate ...transiting planets, 45 with three, 8 with four, and 1 each with five and six. We characterize the dynamical properties of these candidate multi-planet systems. The distribution of observed period ratios shows that the vast majority of candidate pairs are neither in nor near low-order mean-motion resonances. Nonetheless, there are small but statistically significant excesses of candidate pairs both in resonance and spaced slightly too far apart to be in resonance, particularly near the 2:1 resonance. We find that virtually all candidate systems are stable, as tested by numerical integrations that assume a nominal mass-radius relationship. Several considerations strongly suggest that the vast majority of these multi-candidate systems are true planetary systems. Using the observed multiplicity frequencies, we find that a single population of planetary systems that matches the higher multiplicities underpredicts the number of singly transiting systems. We provide constraints on the true multiplicity and mutual inclination distribution of the multi-candidate systems, revealing a population of systems with multiple super-Earth-size and Neptune-size planets with low to moderate mutual inclinations.
Kepler's First Rocky Planet: Kepler-10b Batalha, Natalie M; Borucki, William J; Bryson, Stephen T ...
Astrophysical journal/The Astrophysical journal,
03/2011, Letnik:
729, Številka:
1
Journal Article
Recenzirano
Odprti dostop
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 = 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 {circled plus}, R P = 1.416+0.033 --0.036 R {circled plus}, and Delta *rP = 8.8+2.1 --2.9 g cm--3. Kepler-10b is the smallest transiting exoplanet discovered to date.
When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets ...transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary systems. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47 days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.
TrES-1: The Transiting Planet of a Bright K0 V Star Alonso, Roi; Brown, Timothy M; Torres, Guillermo ...
Astrophysical journal/The Astrophysical journal,
10/2004, Letnik:
613, Številka:
2
Journal Article
Abstract
The Near-Infrared High Throughput Spectrograph (NIHTS) is in operation on the 4.3 m Lowell Discovery Telescope (LDT) in Happy Jack, AZ. NIHTS is a low-resolution spectrograph (
R
∼ 200) that ...operates from 0.86 to 2.45 microns. NIHTS is fed by a custom dichroic mirror which reflects near-infrared wavelengths to the spectrograph and transmits the visible to enable simultaneous imaging with the Large Monolithic Imager (LMI), an independent visible wavelength camera. The combination of premier tracking and acquisition capabilities of the LDT, a several arcminutes field of view on LMI, and high spectral throughput on NIHTS enables novel studies of a number of astrophysical and planetary objects including Kuiper Belt Objects, asteroids, comets, low mass stars, and exoplanet hosts stars. We present a summary of NIHTS operations, commissioning, data reduction procedures with two approaches for the correction of telluric absorption features, and an overview of select science cases that will be pursued by Lowell Observatory, Northern Arizona University, and LDT partners.
Kepler mission results are rapidly contributing to fundamentally new discoveries in both the exoplanet and asteroseismology fields. The data returned from Kepler are unique in terms of the number of ...stars observed, precision of photometry for time series observations, and the temporal extent of high duty cycle observations. As the first mission to provide extensive time series measurements on thousands of stars over months to years at a level hitherto possible only for the Sun, the results from Kepler will vastly increase our knowledge of stellar variability for quiet solar-type stars. Here, we report on the stellar noise inferred on the timescale of a few hours of most interest for detection of exoplanets via transits. By design the data from moderately bright Kepler stars are expected to have roughly comparable levels of noise intrinsic to the stars and arising from a combination of fundamental limitations such as Poisson statistics and any instrument noise. The noise levels attained by Kepler on-orbit exceed by some 50% the target levels for solar-type, quiet stars. We provide a decomposition of observed noise for an ensemble of 12th magnitude stars arising from fundamental terms (Poisson and readout noise), added noise due to the instrument and that intrinsic to the stars. The largest factor in the modestly higher than anticipated noise follows from intrinsic stellar noise. We show that using stellar parameters from galactic stellar synthesis models, and projections to stellar rotation, activity, and hence noise levels reproduce the primary intrinsic stellar noise features.
The Kepler spacecraft is monitoring more than 150,000 stars for evidence of planets transiting those stars. We report the detection of two Saturn-size planets that transit the same Sun-like star, ...based on 7 months of Kepler observations. Their 19.2- and 38.9-day periods are presently increasing and decreasing at respective average rates of 4 and 39 minutes per orbit; in addition, the transit times of the inner body display an alternating variation of smaller amplitude. These signatures are characteristic of gravitational interaction of two planets near a 2:1 orbital resonance. Six radial-velocity observations show that these two planets are the most massive objects orbiting close to the star and substantially improve the estimates of their masses. After removing the signal of the two confirmed giant planets, we identified an additional transiting super-Earth-size planet candidate with a period of 1.6 days.
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