Search

Back in business after a heart-stopping near-shutdown in April, NASA's Kepler space telescope is about to begin an 80-day campaign to search for exoplanets using a novel technique. Called gravitational microlensing, it's based on Einstein's discovery that gravity bends light. That means massive objects in space can act as lenses, focusing the light from objects even farther from Earth. Astronomers have found many cases in which galaxies distort the images of quasars. Microlensing works on a much smaller scale: Individual stars or planets focus the light of more distant stars, making the background star appear to grow brighter and then dim again. By measuring those rising and falling "light curves," Kepler will give astronomers valuable information about planets orbiting other stars—including exoplanets in far-out orbits that other techniques can't detect—and even free-floating planets that don't orbit stars at all.

Our story starts with the German astronomer Johannes Kepler in the early part of the seventeenth century. Though Kepler never witnessed a transit himself, his significance in the story is enormous for two reasons. First, according to Kepler's Third Law, as it is now known, the ratio of the square of a planet's orbital period to the cube of its mean distance from the Sun is the same for all planets. From this law, the relative scale of the solar system can be determined simply by observing the orbital periods of the planets. In fact, Kepler's own estimates of the relative distances of the known planets from the Sun do not differ significantly from

Transit photometry is a promising method for discovering extrasolar planets as small as Earth from spacebased photometers, and several near-term photometric missions are on the drawing board. In particular, NASA’s recently selected Kepler mission is devoted primarily to detecting extrasolar planets. The success of these e!o rts depends in part on the ability to detect transit signatures against the inherent photometric variability of the target stars. While other noise sources such as shot noise and CCD noise are under the control of the instrument designers, this one is not. The photometric variability of solar-like stars presents a fundamental lower limit to the minimum detectable planet radius for a given star and number of observed transits. In this paper we examine the capability of such missions using bolometric data for the only star for which su"cient photometric precision exists to address this question: the Sun. The results indicate that solar-like variability does not prevent the detection of Earth-sized planets even for stars rotating significantly faster than the Sun. Four transits are detectable for mv ! 12 stars with rotation periods as short as " 21 days, while six transitsallowdetectionforstellarrotation periods asshortas" 16days.Indeed, thelimitsposed bysolar-like variability allow for the detection of planets significantly smaller than Earth orbiting Sun-like stars. Planets as small as 0.6 Earth radii exhibitingat least sixtransits can be detected orbiting bright (mv ! 10) solar analogs. Subject headings: methods: data analysis — planetary systems — techniques: photometric

The discovery of Kepler 452b is a milestone in searching for habitable exoplanets. While it has been suggested that Kepler 452b is the first Earth-like exoplanet discovered in the habitable zone of a Sun-like star, its climate states and habitability require quantitative studies. Here, we first use a three-dimensional fully coupled atmosphere–ocean climate model to study the climate and habitability of an exoplanet around a Sun-like star. Our simulations show that Kepler 452b is habitable if CO2 concentrations in its atmosphere are comparable or lower than that in the present-day Earth atmosphere. However, our simulations also suggest that Kepler 452b can become too hot to be habitable if there is the lack of silicate weathering to limit CO2 concentrations in the atmosphere. We also address whether Kepler 452b could retain its water inventory after 6.0 billion years of lifetime. These results in the present Letter will provide insights about climate and habitability for other undiscovered exoplanets similar to Kepler 452b, which may be observable by future observational missions.

Launched in 2009 to seek out worlds beyond the Solar System, the Kepler mission is exceeding expectations. Is it closing in on another Earth?

Numerous telescopes and techniques have been used to find and study extrasolar planets, but none has been more successful than NASA's Kepler Space Telescope. Kepler has discovered the majority of known exoplanets, the smallest planets to orbit normal stars, and the worlds most likely to be similar to our home planet. Most importantly, Kepler has provided our first look at typical characteristics of planets and planetary systems for planets with sizes as small as and orbits as large as those of the Earth., 33 pages, 4 figures, submitted to Nature Insight

We present a search for fast radio transients in targeted observations of planet candidates in the Kepler Field and candidate Astropulse sources.

A large number of observed exoplanets are part of multiple planet systems. Most of these systems are sufficiently close-in to be tidally evolving. In such systems, there is a competition between the excitation caused by planet-planet interactions and tidal damping. Using as an example two multiple planet systems, which host planets in the surface liquid water habitable zone (HZ): Kepler-62 and Kepler-186, we show the importance and effect of both planetary and stellar tides on the dynamical evolution of planets and on the climate of the HZ planets., Comment: Proceedings IAU Symposium No. 310, 2014 (accepted) 1 Figure, black and white

The Kepler mission has discovered over 2500 exoplanet candidates in the first two years of spacecraft data, with approximately 40% of them in candidate multi-planet systems. The high rate of multiplicity combined with the low rate of identified false-positives indicates that the multiplanet systems contain very few false-positive signals due to other systems not gravitationally bound to the target star (Lissauer, J. J., et al., 2012, ApJ 750, 131). False positives in the multi- planet systems are identified and removed, leaving behind a residual population of candidate multi-planet transiting systems expected to have a false-positive rate less than 1%. We present a sample of 340 planetary systems that contain 851 planets that are validated to substantially better than the 99% confidence level; the vast majority of these have not been previously verified as planets. We expect ~2 unidentified false-positives making our sample of planet very reliable. We present fundamental planetary properties of our sample based on a comprehensive analysis of Kepler light curves and ground-based spectroscopy and high-resolution imaging. Since we do not require spectroscopy or high-resolution imaging for validation, some of our derived parameters for a planetary system may be systematically incorrect due to dilution from light due to additional stars in the photometric aperture. None the less, our result nearly doubles the number of verified exoplanets., Comment: 138 pages, 8 Figures, 5 Tables. Accepted for publications in the Astrophysical Journal

The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. Historically, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, 'Dune' planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, Seff, the recently recalculated HZ boundaries are: recent Venus-1.78, runaway greenhouse-1.04, moist greenhouse-1.01, maximum greenhouse-0.35, early Mars-0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late-K and M stars observed by Kepler is in the range of 0.4-0.5., Typo in the third author name corrected. To be published in Proceedings of the National Academy of Sciences (PNAS) special issue on Exoplanets. Article + Supplementary Information available at http://www.pnas.org/content/early/2013/11/20/1309107110.full.pdf+html?with-ds=yes

Determining whether Earth-like planets are common or rare looms as a touchstone in the question of life in the universe. We searched for Earth-size planets that cross in front of their host stars by examining the brightness measurements of 42,000 stars from National Aeronautics and Space Administration's Kepler mission. We found 603 planets, including 10 that are Earth size (1-2 Earth-radii) and receive comparable levels of stellar energy to that of Earth (within a factor of four). We account for Kepler's imperfect detectability of such planets by injecting synthetic planet-caused dimmings into the Kepler brightness measurements and recording the fraction detected. We find that $11\pm4%$ of Sun-like stars harbor an Earth-size planet receiving between one and four times the stellar intensity as Earth. We also find that the occurrence of Earth-size planets is constant with increasing orbital period (P), within equal intervals of logP up to $\sim200$ d. Extrapolating, one finds $5.7^{+1.7}_{-2.2}%$ of Sun-like stars harbor an Earth-size planet with orbital periods of 200-400 d., Main text: 6 pages, 5 figures, 1 table. Supporting information: 54 pages, 17 pages, 3 tables. Published in the Proceedings of the National Academy of Sciences available at http://www.pnas.org/cgi/doi/10.1073/pnas.1319909110

Kepler-78 (KIC 8435766) was identified by Sanchis-Ojeda et al. (2013) as harbouring a transiting planet of 1.16 times the size of the Earth and an orbital period of only 8.5 hours. While the exquisite Kepler photometry was able to determine its radius and period, the mass of the planet (and thus its mean density) remained unconstrained in the absence of precise radial-velocity measurements. Here we present an accurate mass measurement of Kepler-78b using the HARPS-N spectrograph, recently installed on the Telescopio Nazionale Galileo (INAF) at the Roque de los Muchachos Observatory, La Palma, Spain. These new data yield a mass of 1.86 Earth masses. The resulting mean density of the planet is 5.57 grams per cubic centimetre, which is similar to that of the Earth and implies a composition of iron and rock. Kepler-78b, which orbits a Sun-like star called Kepler 78 located in the Cygnus constellation at a distance of about 400 light years from us, is now the smallest exoplanet for which both the mass and radius are known accurately., 10 Pages, 8 figures, 5 tables, data. Nature, 2013 (published online Oct. 30)

Kepler vaulted into the heavens on March 7, 2009, initiating NASA’s search for Earth-size planets orbiting Sun-like stars in the habitable zone, where liquid water could exist on the planetary surface and support alien biology. Never before has there been a photometer capable of reaching a precision near 20 ppm in 6.5 hours while conducting nearly continuous and uninterrupted observations for several years. The flood of exquisite photometric data over the last 4 years on 190,000+ stars has provoked a watershed of results. Over 2,700+ candidate planets have been identified of which an astounding 1171 orbit 467 stars. Over 120+ planets have confirmed or validated and the data have also led to a resounding revolution in asteroseismology. Recent discoveries include Kepler-62 with 5 planets total of which 2 are in the habitable zone, and are 1.4 and 1.7 times the radius of the Earth. Designing and building the Kepler photometer and the software systems that process and analyze the resulting data presented a daunting set of challenges, including how to manage the large data volume, how to detect miniscule transit signatures against stellar variability and instrumental effects, and how to review hundreds of diagnostics produced for each of ~20,000 candidate transit signatures. The challenges continue into flight operations, as the photometer and spacecraft have experienced aging and changes in hardware performance over the course of time. The success of Kepler sets the stage for TESS, NASA’s next mission to detect Earth’s closest cousins.

The currently observed architectures of extrasolar planetary systems trace the processes of planetary formation and evolution. Until recently, Jovian-size planets provided nearly all of the observational constraints. From Doppler studies, we detect a steeply rising planet mass distribution down to at least 3 Earth-masses for planets orbiting inside of 0.25 AU. The planet size distribution from Kepler also shows a steep rise with decreasing size, but with a plateau in the occurrence rate for 1{2.8 times Earth size. Analyses of the Kepler data support the bottom-up picture of planet formation by core accretion.

We use the optical and near-infrared photometry from the Kepler Input Catalog to provide improved estimates of the stellar characteristics of the smallest stars in the Kepler target list. We find 3897 dwarfs with temperatures below 4000K, including 64 planet candidate host stars orbited by 95 transiting planet candidates. We refit the transit events in the Kepler light curves for these planet candidates and combine the revised planet/star radius ratios with our improved stellar radii to revise the radii of the planet candidates orbiting the cool target stars. We then compare the number of observed planet candidates to the number of stars around which such planets could have been detected in order to estimate the planet occurrence rate around cool stars. We find that the occurrence rate of 0.5-4 Earth radius planets with orbital periods shorter than 50 days is 0.90 (+0.04/-0.03) planets per star. The occurrence rate of Earth-size (0.5-1.4 Earth radius) planets is constant across the temperature range of our sample at 0.51 (+0.06/-0.05) Earth-size planets per star, but the occurrence of 1.4-4 Earth radius planets decreases significantly at cooler temperatures. Our sample includes 2 Earth-size planet candidates in the habitable zone, allowing us to estimate that the mean number of Earth-size planets in the habitable zone is 0.15 (+0.13/-0.06) planets per cool star. Our 95% confidence lower limit on the occurrence rate of Earth-size planets in the habitable zones of cool stars is 0.04 planets per star. With 95% confidence, the nearest transiting Earth-size planet in the habitable zone of a cool star is within 21 pc. Moreover, the nearest non-transiting planet in the habitable zone is within 5 pc with 95% confidence., We corrected an error in the code that calculates the number of stars for which a given planet could have been detected. The stellar parameters, planet parameters, and fraction of stars with planets did not change significantly. However, our estimate of the occurrence rate of habitable-zone, Earth-sized planets increased. Accepted for publication in ApJ. Machine readable tables in right sidebar

Currently, the most popular way of detecting Extra-solar planets (exoplanets) is via the Transit Method. This method is limited only to planets with orbits such that we observe them transiting their host star. In this work in progress, we propose to identify non-transiting exoplanets in the data currently being collected by the Kepler Space Telescope by detecting orbital phase reflected light variations. Since such variations are due to light from the host star reflected by the planet, we expect this method to work best on closely orbitting large planets. Using the Metropolis-Hastings Monte Carlo and Nested Sampling algorithms, we will determine the presence or absence of nontransiting planets and estimate their orbital parameters such as, orbital inclination, semi-major axis, period, and eccentricity. Our estimates indicate that the development of this technique has the potential to double the number of detectable planets in the Kepler data sets. Here we demonstrate feasibility using portions of data from one of the first transiting planets detected by Kepler, HAT-P-7b.

We evaluate the extent to which newly detected exoplanetary systems containing at least four planets adhere to a generalized Titius-Bode (TB) relation. We find that the majority of exoplanet systems in our sample adhere to the TB relation to a greater extent than the Solar System does, particularly those detected by the Kepler mission. We use a generalized TB relation to make a list of predictions for the existence of 141 additional exoplanets in 68 multiple-exoplanet systems: 73 candidates from interpolation, 68 candidates from extrapolation. We predict the existence of a low-radius (R < 2.5 Earth Radii) exoplanet within the habitable zone of KOI-812 and that the average number of planets in the habitable zone of a star is 1-2. The usefulness of the TB relation and its validation as a tool for predicting planets will be partially tested by upcoming Kepler data releases., 23 pages, 7 figures, 3 tables Accepted by MNRAS

NASA's Kepler Mission was launched on March 6, 2009 with the goal of determining the frequency of Earth-size planets in the habitable zone of solar-like stars using the transit photometry method. Kepler's driving design requirement was the ability to detect the 84-ppm change in brightness as an Earth-size planet transits its host star. As such, stability of the instrument and continuity of the data are keys for success. Kepler is beginning the third year of the planned 3.5 years of data collection and has already revolutionized the field of extrasolar planets, detecting over 2,300 planet candidates, the first Earth-size planets, the first circumbinary planets, and over 360 multiple-planet systems. The project has proposed an extension of the mission to NASA so that Kepler can continue collecting data and results for another four years.

New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1,091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multi-quarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and those at longer orbital periods (123% for candidates outside of 50-day orbits versus 85% for candidates inside of 50-day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1-- Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant., Comment: Submitted to ApJS. Machine-readable tables are available at http://kepler.nasa.gov, http://archive.stsci.edu/kepler/results.html, and the NASA Exoplanet Archive

How do we know the mass of a planet, asteroid, or of a distant star? If we are told that Saturn is light enough to float on water, that a tablespoon of neutron star stuff would weigh more than the Earth, or that there is a black hole at the center of our galaxy, how are those facts known? If you say, “You need to somehow use gravity as a probe to determine mass” you will be right. There are two ways to do this, one difficult and often uncertain; the other quite precise, depending on the quality of the observational data. In the first method, the mass of a body can be inferred by its perturbing effects on other bodies. This means there must be well defined orbits of other bodies that have passed close enough to the mystery mass to figure it out. Of course, the perturbed body need not be a another orbiting planet: in the rare case that a comet (or even a space vehicle) passes close by, the encounter may allow measurement of how much the body bends the visitor’s path. The second, vastly preferable method employs Kepler’s Third Law. It requires a body orbiting the mass we want to measure. That is, far and away, the most precise measuring tool of a body’s mass. Without another body whirling around the star, planet or asteroid, one must fall back on other, imperfect means.

We present a framework to conservatively estimate the probability that any particular planet-like transit signal observed by the Kepler mission is in fact a planet, prior to any ground-based follow-up efforts. We use Monte Carlo methods based on stellar population synthesis and Galactic structure models, and report a priori false positive probabilities for every Kepler Object of Interest in tabular form, assuming a 20% intrinsic occurrence rate of close-in planets in the radius range 0.5 Rearth < Rp < 20 Rearth. Almost every candidate has FPP 10% to, Revision including results of calculations of individual FPPs for all KOIs as well as an additional discussion section regarding the relationship of our calculations to BLENDER. ApJ in press

Kepler is NASA's first space mission dedicated to the study of exoplanets. The primary scientific goal is statistical - to estimate the frequency of planetary systems associated with sun-like stars, especially the detection of earth-size planets in the Habitable Zones. Kepler was launched into an Earth-trailing heliocentric "drift-away" orbit (period = 372 days) in March 2009. The instrument detects the faint photometric signals of transits of planets across the stellar disks of those systems with orbital planes fortuitously oriented in our line-of-sight. Since the probability of such alignments is small Kepler must observe a large number of stars. In fact, Kepler is monitoring approximately 150,000 stars with a 30-minute cadence. These scientific requirements led to the choice of a classical Schmidt telescope, and requirements on field-of-view (FOV), throughput, spectral bandpass, image quality, scattered light, thermal and opto-mechanical stability and in-flight adjustment authority. We review the pre-launch integration, alignment and test program, and we describe the in-flight commissioning that optimized the optical performance of the observatory. The stability of the flight system has enabled increasing recognition of small effects and increasing sophistication in data processing algorithms. Astrophysical noise arising from intrinsic stellar variability is now the dominant term in the photometric error budget.

Kepler is NASA’s first space mission dedicated to the study of exoplanets. The primary scientific goal is statistical Š to estimate the frequency of planetary systems associated with sun-like stars. Kepler was launched into an Earth-trailing heliocentric “drift-away” orbit in March 2009, and is monitoring 150,000 stars. The instrument detects the faint photometric signals of transits of those systems whose orbital planes are oriented in our line-of-sight. An Earth-Sun analog will produce a transit depth of 80 parts per million (ppm ), lasting for at most a few tens of hours, and repeating once per “year”. The instrumentation was designed to provide photometric data with a precision of 20 parts per million in 6.5 hours for 12 th magnitude stars, resulting in a signal-to-noise ratio of 4 for an Earth-Sun transit. The stability of the flight system enables the precision of the data that reveal subtle instrumental and astrophysical effects th at in turn allow a deeper understanding of the performance of the hardware, to enhanced operational procedures, and to novel post-processing of the data. The data are approaching the sensitivity needed to detect transits of terrestrial planets. Intrinsic stellar variability is now the most significant component of the phot ometric error budget. Keywords: Kepler mission, exoplanets, transits, telescope, focal plane, CCD, project management, systems engineering

The Kepler spacecraft launched on March 7, 2009, initiating NASA’s rst search for Earth-size planets orbiting Sun-likestars. Since launch, Kepler has announced the discovery of 17 exoplanets, including a system of six transiting a Sun-likestar, Kepler-11, and the rst con rmed rocky planet, Kepler-10b, with a radius of 1.4 that of Earth. Kepler is proving tobe a cornucopia of discoveries: it has identi ed over 1200 candidate planets based on the rst 120 days of observations,including54thatareinornearthehabitablezoneoftheirstars,and68thatare1.2Earthradiiorsmaller. Anastounding408of these planetary candidates are found in 170 multiple systems, demonstrating the compactness and atness of planetarysystems composed of small planets. Never before has there been a photometer capable of reaching a precision near 20ppm in 6.5 hours and capable of conducting nearly continuous and uninterrupted observations for months to years. Inaddition to exoplanets, Kepler is providing a wealth of astrophysics, and is revolutionizing the eld of asteroseismology.Designingandbuildingthe Kepler photometerandthesoftwaresystemsthatprocessandanalyzetheresultingdatatomakethe discoveries presented a daunting set of challenges, including how to manage the large data volume. The challengescontinueinto ight operations,as the photometeris sensitive toits thermalenvironment,complicatingthe taskof detecting84 ppm drops in brightness correspondingto Earth-size planets transiting Sun-like stars.Keywords: Kepler Mission , exoplanet, transit, photometry,data compression,systematic error correction

On 1 February 2011 the Kepler Mission released data for 156,453 stars observed from the beginning of the science observations on 2 May through 16 September 2009. There are 1235 planetary candidates with transit like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class-sizes; 68 candidates of approximately Earth-size (radius < 1.25 Earth radii), 288 super-Earth size (1.25 Earth radii < radius < 2 Earth radii), 662 Neptune-size (2 Earth radii < radius < 6 Earth radii), 165 Jupiter-size (6 Earth radii < radius < 15 Earth radii), and 19 up to twice the size of Jupiter (15 Earth radii < radius < 22 Earth radii). In the temperature range appropriate for the habitable zone, 54 candidates are found with sizes ranging from Earth-size to larger than that of Jupiter. Five are less than twice the size of the Earth. Over 74% of the planetary candidates are smaller than Neptune. The observed number versus size distribution of planetary candidates increases to a peak at two to three times Earth-size and then declines inversely proportional to area of the candidate. Our current best estimates of the intrinsic frequencies of planetary candidates, after correcting for geometric and sensitivity biases, are 6% for Earth-size candidates, 7% for super-Earth size candidates, 17% for Neptune-size candidates, and 4% for Jupiter-size candidates. Multi-candidate, transiting systems are frequent; 17% of the host stars have multi-candidate systems, and 33.9% of all the candidates are part of multi-candidate systems., 106 pages, 15 figures, contains tables of candidates. Submitted to ApJ

In addition to its search for extra-solar planets, the NASA Kepler Mission provides exquisite data on stellar oscillations. We report the detections of oscillations in 500 solartype stars in the Kepler field of view, an ensemble that is large enough to allow statistical studies of intrinsic stellar properties (such as mass, radius and age) and to test theories of stellar evolution. We find that the distribution of observed masses of these stars shows intriguing differences to predictions from models of synthetic stellar populations in the Galaxy., 20 pages, including on-line supporting material

We report the distribution of planets as a function of planet radius (R_p), orbital period (P), and stellar effective temperature (Teff) for P < 50 day orbits around GK stars. These results are based on the 1,235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 Earth radii (Re). For each of the 156,000 target stars we assess the detectability of planets as a function of R_p and P. We also correct for the geometric probability of transit, R*/a. We consider first stars within the "solar subset" having Teff = 4100-6100 K, logg = 4.0-4.9, and Kepler magnitude Kp < 15 mag. We include only those stars having noise low enough to permit detection of planets down to 2 Re. We count planets in small domains of R_p and P and divide by the included target stars to calculate planet occurrence in each domain. Occurrence of planets varies by more than three orders of magnitude and increases substantially down to the smallest radius (2 Re) and out to the longest orbital period (50 days, ~0.25 AU) in our study. For P < 50 days, the radius distribution is given by a power law, df/dlogR= k R^��. This rapid increase in planet occurrence with decreasing planet size agrees with core-accretion, but disagrees with population synthesis models. We fit occurrence as a function of P to a power law model with an exponential cutoff below a critical period P_0. For smaller planets, P_0 has larger values, suggesting that the "parking distance" for migrating planets moves outward with decreasing planet size. We also measured planet occurrence over Teff = 3600-7100 K, spanning M0 to F2 dwarfs. The occurrence of 2-4 Re planets in the Kepler field increases with decreasing Teff, making these small planets seven times more abundant around cool stars than the hottest stars in our sample. [abridged], Submitted to ApJ, 22 pages, 10 figures

Kepler is NASA's first mission capable of detecting Earth-size planets orbiting in the habitable zone of stars other than the Sun. Kepler comprises a space telescope designed to continuously monitor the brightnesses of more than 100,000 target stars, and a ground segment to analyze the measured stellar light curves and detect the signatures of orbiting planets. In order to detect Earth-size planets orbiting Sun-like stars Kepler was designed to provide unprecedented photometric sensitivity and stability. This paper addresses some of the technical challenges encountered during the development of the Kepler mission and the measures taken to overcome them. Early scientific results are summarized.1 2

When an extrasolar planet passes in front of its star (transits), 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 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 that reveal six transiting planets, five with orbital periods between 10 and 47 days plus a sixth one with a longer period. The five inner planets are among the smallest whose masses and sizes 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., Comment: published in Nature

The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in a habitable zone (HZ) of solar-like stars. Recent discoveries based on the Doppler-velocity technique have shown that many stars have giant planets, but this technique cannot detect Earth-size planets orbiting solar-like stars. The Kepler Mission is based on observing transits and is designed specifically to determine the frequency of terrestrial planets in a HZ. It was launched and is now monitoring 150,000 solar-like stars to detect patterns of transits that provide the size of the planet relative to the star and its orbital period. Combining these measurements with ground-based spectroscopy fixes the stellar parameters, the planet radius, orbital distance, and location relative to the HZ. Hundreds of terrestrial planets should be discovered before the mission ends, implying that life might be ubiquitous in our galaxy. Five large planets have been discovered already.

Detecting Distant Planets More than 400 planets have been detected outside the solar system, most of which have masses similar to that of the gas giant planet, Jupiter. Borucki et al. (p. 977 , published online 7 January) summarize the planetary findings derived from the first six weeks of observations with the Kepler mission whose objective is to search for and determine the frequency of Earth-like planets in the habitable zones of other stars. The results include the detection of five new exoplanets, which confirm the existence of planets with densities substantially lower than those predicted for gas giant planets.

The Kepler Mission began its 3.5-year photometric monitoring campaign in May 2009 on a select group of approximately 150,000 stars. The stars were chosen from the ~half million in the field of view that are brighter than 16th magnitude. The selection criteria are quantitative metrics designed to optimize the scientific yield of the mission with regards to the detection of Earth-size planets in the habitable zone. This yields more than 90,000 G-type stars on or close to the Main Sequence, >20,000 of which are brighter than 14th magnitude. At the temperature extremes, the sample includes approximately 3,000 M-type dwarfs and a small sample of O and B-type MS stars, Submitted to Astrophysical Journal Letters

Of the over 400 known1 exoplanets, there are about 70 planets that transit their central star, a situation that permits the derivation of their basic parameters and facilitates investigations of their atmospheres. Some short-period planets2, including the first terrestrial exoplanet3,4 (CoRoT-7b), have been discovered using a space mission5 designed to find smaller and more distant planets than can be seen from the ground. Here we report transit observations of CoRoT-9b, which orbits with a period of 95.274 days on a low eccentricity of 0.11 ± 0.04 around a solar-like star. Its periastron distance of 0.36 astronomical units is by far the largest of all transiting planets, yielding a ‘temperate’ photospheric temperature estimated to be between 250 and 430 K. Unlike previously known transiting planets, the present size of CoRoT-9b should not have been affected by tidal heat dissipation processes. Indeed, the planet is found to be well described by standard evolution models6 with an inferred interior composition consistent with that of Jupiter and Saturn.

The Kepler Mission Science Operations Center (SOC) performs several critical functions including managing the ~156,000 target stars, associated target tables, science data compression tables and parameters, as well as processing the raw photometric data downlinked from the spacecraft each month. The raw data are first calibrated at the pixel level to correct for bias, smear induced by a shutterless readout, and other detector and electronic effects. A background sky flux is estimated from ~4500 pixels on each of the 84 CCD readout channels, and simple aperture photometry is performed on an optimal aperture for each star. Ancillary engineering data and diagnostic information extracted from the science data are used to remove systematic errors in the flux time series that are correlated with these data prior to searching for signatures of transiting planets with a wavelet-based, adaptive matched filter. Stars with signatures exceeding 7.1 sigma are subjected to a suite of statistical tests including an examination of each star's centroid motion to reject false positives caused by background eclipsing binaries. Physical parameters for each planetary candidate are fitted to the transit signature, and signatures of additional transiting planets are sought in the residual light curve. The pipeline is operational, finding planetary signatures and providing robust eliminations of false positives., 8 pages, 3 figures

The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.

The Kepler observatory was designed to discover transits by Earth‐like planets orbiting Sun‐like stars. Its first major discoveries, however, are hot objects in close orbits around main‐sequence stars. These are likely to be white‐dwarf remnants of stars that have transferred mass to the present‐day main sequence stars. These particular main‐sequence stars are among the Kepler targets because they are bright. The question is: how many of the other Kepler target stars are also orbited by white dwarfs? We have shown that several hundred white dwarfs are likely to transit the Kepler target stars during the mission. In some cases, the signature will be dominated by gravitational lensing, producing distinctive “antitransits”. Neutron stars and black holes may also be discovered this way. The lensing signature provides a measurement of the gravitational mass of the compact object. Through the discovery of both transits and antitransits caused by white dwarfs, Kepler will discover and study binaries that have already experienced a phase of mass transfer or a common envelope phase. Thus, Kepler will become a premier tool for the study of interacting binaries. During the next phase of interaction, some of the Kepler binaries may become nuclear‐burning white dwarfs, and may be candidates for Type Ia supernovae or accretion‐induced collapse.

Ten days of photometric data were obtained during the commissioning phase of the Kepler mission, including data for the previously known giant transiting exoplanet HAT-P-7b. The data for HAT-P-7b show a smooth rise and fall of light from the planet as it orbits its star, punctuated by a drop of 130 +/- 11 parts per million in flux when the planet passes behind its star. We interpret this as the phase variation of the dayside thermal emission plus reflected light from the planet as it orbits its star and is occulted. The depth of the occultation is similar in photometric precision to the detection of a transiting Earth-size planet for which the mission was designed.

Kepler is a Discovery-class mission designed to determine the frequency of Earth-size and smaller planets in and near the habitable zone (HZ) of spectral type F through M dwarf stars. The instrument consists of a 0.95 m aperture photometer to do high-precision photometry of 100,000 solar-like stars to search for patterns of transits. The depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. Multi-band ground-based observation of these stars is currently underway to estimate the stellar parameters and to choose appropriate targets. With these parameters, the true planet radius and orbit scale—hence the relation to the HZ—can be determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four-year mission, several hundred terrestrial planets should be discovered with periods between 1–400 days, if such planets are common. A null result would imply that terrestrial planets are rare. Based on the results of the recent Doppler-velocity discoveries, over a thousand giant planets will also be found. Information on the albedos and densities of those giants showing transits will be obtained. The mission is now in Phase C/D development and is scheduled for launch in 2008 into a 372-day heliocentric orbit.

This report is a comprehensive study of the search for and study of planets around other stars (exoplanets). The young but maturing field of exoplanets is perhaps one of the most compelling fields of study in science today--both because of the discoveries made to date on giant planets around other stars, and because the detection of planets just like our Earth ('Earth analogs') is at last within reach technologically. In the Report we outline the need for a vigorous research program in exoplanets to understand our place in the cosmos: whether planets like our home Earth are a common or rare outcome of cosmic evolution. The strategy we developed is intended to address the following fundamental questions, in priority order, within three distinct 5-yr long phases, over a 15 year period: (1) What are the physical characteristics of planets in the habitable zones around bright, nearby stars? (2) What is the architecture of planetary systems? (3) When, how and in what environments are planets formed? The Report recommends a two-pronged strategy for the detection and characterization of planets the size of the Earth. For stars much less massive and cooler than our Sun (M-dwarfs), existing ground-based techniques including radial velocitymore » and transit searches, and space-based facilities both existing and under development such as Spitzer and JWST, are adequate for finding and studying planets close to the mass and size of the Earth. Conducted in parallel with the M-dwarf strategy is one for the more challenging observations of the hotter and brighter F, G, and K stars, some of which are very close in properties to our Sun, in which the frequency of Earth-sized planets is assessed with Corot and Kepler, but new space missions are required for detection and study of specific Earth-mass and Earth-sized objects. Our Task Force concludes that the development of a space-based astrometric mission, narrowly-focused to identify specific nearby stars with Earth-mass planets, followed by direct detection and study via a spaceborne coronagraph/occulter or interferometric mission, is the most robust approach to pursue. Ground and space-based microlensing programs pursued in parallel would provide complementary information on planetary system architectures on galactic scales. The program for F, G, and K stars must be preceded, at the beginning of the strategy, by broad yet detailed technical assessments to determine whether the astrometric and direct detection technologies will be ready in the time frames envisioned (the second and third 5-yr periods, respectively). Also measurement of dust around nearby candidate stars must be undertaken early to determine whether typical systems are clean enough to make direct detection feasible. Alternative strategies are discussed should problems arise in any of these areas. Finally, the Task Force lays out recommended programs in ground-based observations of larger planets, of planet-forming disks, and theoretical and laboratory studies crucial to interpreting and understanding the outcome of the planet search and characterization observations.« less

International audience; After a decade rich in giant exoplanet detections, observation techniques have now reached the sensitivity to gain information on the physical structure and chemical content of some of the detected planets and also to find planets of less than 10 M?. The detection and characterization of Earth-like planets is approaching rapidly and dedicated space observatories are already in operation (CoRoT) or in the development phase (Kepler, Darwin and TPF-I/C). In this paper, we explore the domain of terrestrial planets, emphasizing habitable worlds. We discuss the possibility of performing a spectral characterization of their properties using the next generation of astronomical instruments.

Planets less massive than about 10 MEarth are expected to have no massive H-He atmosphere and a cometary composition (50% rocks, 50% water, by mass) provided they formed beyond the snowline of protoplanetary disks. Due to inward migration, such planets could be found at any distance between their formation site and the star. If migration stops within the habitable zone, this will produce a new kind of planets, called Ocean-Planets. Ocean-planets typically consist in a silicate core, surrounded by a thick ice mantle, itself covered by a 100 km deep ocean. The existence of ocean-planets raises important astrobiological questions: Can life originate on such body, in the absence of continent and ocean-silicate interfaces? What would be the nature of the atmosphere and the geochemical cycles ? In this work, we address the fate of Hot Ocean-Planets produced when migration ends at a closer distance. In this case the liquid/gas interface can disappear, and the hot H2O envelope is made of a supercritical fluid. Although we do not expect these bodies to harbor life, their detection and identification as water-rich planets would give us insight as to the abundance of hot and, by extrapolation, cool Ocean-Planets., 47 pages, 6 Fugures, regular paper. Submitted to Icarus

The Kepler Mission has found thousands of planetary candidates with radii between 1 and 4 . These planets have no analogues in our own solar system, providing an unprecedented opportunity to understand the range and distribution of planetary compositions allowed by planet formation and evolution. A precise mass measurement is usually required to constrain the possible composition of an individual super-Earth-sized planet, but these measurements are difficult and expensive to make for the majority of Kepler planet candidates (PCs). Fortunately, adopting a statistical approach helps us to address this question without them. In particular, we apply hierarchical Bayesian modeling to a subsample of Kepler PCs that is complete for days and and draw upon interior structure models that yield radii largely independent of mass by accounting for the thermal evolution of a gaseous envelope around a rocky core. Assuming the envelope is dominated by hydrogen and helium, we present the current-day composition distribution of the sub-Neptune-sized planet population and find that H+He envelopes are most likely to be ∼1% of these planets’ total masses with an intrinsic scatter of ±0.5 dex. We address the gaseous/rocky transition and illustrate how our results do not result in a one-to-one relationship between mass and radius for this sub-Neptune population; accordingly, dynamical studies that wish to use Kepler data must adopt a probabilistic approach to accurately represent the range of possible masses at a given radius.

In this we design a simple and insightful way to achieve Kepler?s first two laws for planets. The approach is quite different from what we have done for the Earth before. It is because the planet?Sun distance can be determined only through the Earth?Sun distance in the analysis. By applying the law of equal areas for the Earth and the observed angular speeds of a planet over the Sun, the law of equal areas for planets can be re-constructed. Furthermore, for the periodicity of a planet to the Sun, the distance from each planet to the Sun may be expressed as an angular periodic function. By coordinating with the observed data, this periodic distance function depicts an exact elliptical path. Here, we apply relatively easy mathematical skills to illustrate the invariant forms of planetary motions and indicate the key factors used to analyse the motions in complicated planetary systems.

SIM PlanetQuest is a space-borne Michelson interferometer with a nine meter baseline that will survey ~200 stars within 30 parsecs for terrestrial mass planets. Ultra-precise astrometric observations will reveal the gravitational wobble of the target star (due to a planetary companion) against an inertial frame of reference stars located within a 1.5 degree radius. Here, we report the results of multiple Monte Carlo simulations which have modeled SIM's ability to detect and determine the orbital parameters and masses of the terrestrial mass planets around its potential sample of target stars. We find that SIM will detect 80% of the planets in the 60 star sample. Out of those planets SIM detects, we will be able to estimate the masses of at least 50% of the planets to 30%. Whether SIM should observer 60 or 240 stars, will be aided by the results of the Kepler mission which will provide statistics on the frequency of terrestrial-mass planets around solar type stars. By determining the orbital phase of the planet, SIM will be able to assist TPF-C by telling it when to look to ensure that the planet will be outside the TPF-C 62 mas inner working angle. Furthermore, the masses determined by SIM will not suffer from the msini ambiguity inherent in radial velocity surveys.

Detection of Earth sized extra-solar planets by the transit method requires measurement of quite small variations (~8x10 -5 ) in the brightness of candidate stars. Noise contribute d by hot pixels in CCD detectors operating in the space environment, among other noise sources, must be understood and controlled in order to design transit experiments like the Kepler Mission, which will attempt to measure the distribution of planets as small as the Earth around solar type stars from space. We have analyzed the hot pixel statistics for CCD detectors on several operating space instruments and conclude that neither the amplitude nor the variability of hot pixels will significantly impair the ability of the Kepler Mission to detect transits of earth sized planets transiting solar type stars. The Kepler Mission is currently in the design stage and is expected to begin operation in 2007. Keywords: extra-solar planets, planet detection, photometry, CCDs, space observatories, transit method, Kepler Mission, hot pixels

The Kepler Mission is a search for terrestrial planets with the design optimized for detecting Earth-size planets in the habitable zone (HZ) of solar-like stars. In addition, the mission has a broad detection capability for a wide range of planetary sizes, planetary orbits and spectral types of stars. The mission is in the midst of the development phase with good progress leading to the preliminary design review later this year. Long lead procurements are well under way. An overview in all areas is presented including both the flight system (photometer and spacecraft) and the ground system. Launch is on target for 2007 on a Delta II.