The Occurrence Rate of Earth Analog Planets Orbiting Sunlike Stars

Abstract

Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine η_Earth, the fraction of Sunlike stars that have planets like Earth. When a planet 'transits' or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler's science team has determined sizes, surface temperatures, orbit sizes and periods for over a thousand new planet candidates. In this paper, we characterize the period probability distribution function of the super-Earth and Neptune planet candidates with periods up to 132 days, and find three distinct period regimes. For candidates with periods below 3 days the density increases sharply with increasing period; for periods between 3 and 30 days the density rises more gradually with increasing period, and for periods longer than 30 days, the density drops gradually with increasing period. We estimate that 1% to 3% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of Feb 2011. This estimate of is based on extrapolation from a fiducial subsample of the Kepler planet candidates that we chose to be nominally 'complete' (i.e., no missed detections) to the realm of the Earth-like planets, by means of simple power law models. The accuracy of the extrapolation will improve as more data from the Kepler mission is folded in. Accurate knowledge of η_Earth is essential for the planning of future missions that will image and take spectra of Earthlike planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions.

Accepted for publication in the Astrophysical Journal. 19 pages, 8 figures. Minor text revisions, as requested by the scientific editor. Included an additional figure. No changes in the scientific results

References in corpus (3)

• Power-law distributions in empirical data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters

Cited by in corpus (57)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The PLATO 2.0 Mission
• The false positive rate of Kepler and the occurrence of planets
• The Occurrence and Architecture of Exoplanetary Systems
• Prevalence of Earth-size planets orbiting Sun-like stars
• The Occurrence Rate of Small Planets around Small Stars
• Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run
• Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets
• A stellar-mass-dependent drop in planet occurrence rates
• A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)
• A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around kepler m-dwarfs
• Exoplanet population inference and the abundance of Earth analogs from noisy, incomplete catalogs
• The Derivation, Properties and Value of Kepler's Combined Differential Photometric Precision
• Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)
• How to Characterize Habitable Worlds and Signs of Life
• 25 Years of Self-Organized Criticality: Solar and Astrophysics
• Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on The Entire 48 Month Dataset (Q1-Q17 DR24)
• Revealing A Universal Planet-Metallicity Correlation For Planets of Different Sizes Around Solar-Type Stars
• The Occurrence of Rocky Habitable Zone Planets Around Solar-Like Stars from Kepler Data
• A Statistical Reconstruction of the Planet Population Around Kepler Solar-Type Stars
• Exoplanet Biosignatures: Observational Prospects
• A Catalog of Kepler Habitable Zone Exoplanet Candidates
• Influence of Stellar Multiplicity On Planet Formation. I. Evidence of Suppressed Planet Formation Due to Stellar Companions Within 20 AU and Validation of Four Planets From the Kepler Multiple Planet Candidates
• Fast Rise of "Neptune-Size" Planets ($4-8R_{\mathrm{Earth}}$) from $P\sim 10$ to $\sim 250$ days -- Statistics of Kepler Planet Candidates Up to $\sim 0.75\mathrm{AU}$
• Searching the Entirety of Kepler Data. II. Occurrence Rate Estimates for FGK Stars
• Superhabitable Worlds
• Synthesizing Exoplanet Demographics from Radial Velocity and Microlensing Surveys, II: The Frequency of Planets Orbiting M Dwarfs
• Terrestrial, Habitable-Zone Exoplanet Frequency from Kepler
• Measuring Transit Signal Recovery in the Kepler Pipeline II: Detection Efficiency as Calculated in One Year of Data
• Accounting for Incompleteness due to Transit Multiplicity in Kepler Planet Occurrence Rates
• Exoplanet Classification and Yield Estimates for Direct Imaging Missions
• Low False-Positive Rate of Kepler Candidates Estimated From A Combination Of Spitzer And Follow-Up Observations
• Swansong Biospheres: Refuges for life and novel microbial biospheres on terrestrial planets near the end of their habitable lifetimes
• The Influence of Thermal Evolution in the Magnetic Protection of Terrestrial Planets
• On The History and Future of Cosmic Planet Formation
• Adaptive Optics Images III: 87 Kepler Objects of Interest
• A Novel Method to Photometrically Constrain Orbital Eccentricities: Multibody Asterodensity Profiling (MAP)
• Accounting for Multiplicity in Calculating Eta Earth
• Architectures of Exoplanetary Systems. II: An Increase in Inner Planetary System Occurrence Toward Later Spectral Types for Kepler's FGK Dwarfs
• Eccentricity Driven Climate Effects in the Kepler-1649 System
• Scaling K2. IV. A Uniform Planet Sample for Campaigns 1-8 and 10-18
• Variability due to climate and chemistry in observations of oxygenated Earth-analogue exoplanets
• In Search of Future Earths: Assessing the possibility of finding Earth analogues in the later stages of their habitable lifetimes
• Probing the capability of future direct imaging missions to spectrally constrain the frequency of Earth-like planets
• A Catalog of Stellar Evolution Profiles and the Effects of Variable Composition on Habitable Systems
• Planet occurrence rate density models including stellar effective temperature
• Scaling K2. III. Comparable Planet Occurrence in the FGK Samples of Campaign 5 and Kepler
• Predicting multiple planet stability and habitable zone companions in the TESS era
• Eta-Earth Revisited II: Deriving a Maximum Number of Earth-like Habitats in the Galactic Disk
• Sensitivity Analyses of Exoplanet Occurrence Rates from Kepler and Gaia
• Formulation and Resolutions of the Red Sky Paradox
• Revising Properties of Planet-host Binary Systems II: Apparent Near-Earth Analog Planets in Binaries Are Often Sub-Neptunes
• Modal noise mitigation for high-precision spectroscopy using a photonic reformatter
• Relative occurrence rates of terrestrial planets orbiting FGK stars
• Direct High-Resolution Imaging of Earth-Like Exoplanets
• Exploring Long-period Architectures: Four New Planet Candidates from Kepler with Periods >342 days