Quantitative estimates of the surface habitability of Kepler-452b

Abstract

Kepler-452b is currently the best example of an Earth-size planet in the habitable zone of a sun-like star, a type of planet whose number of detections is expected to increase in the future. Searching for biosignatures in the supposedly thin atmospheres of these planets is a challenging goal that requires a careful selection of the targets. Under the assumption of a rocky-dominated nature for Kepler-452b, we considered it as a test case to calculate a temperature-dependent habitability index, $h_{050}$, designed to maximize the potential presence of biosignature-producing activity (Silva et al.\ 2016). The surface temperature has been computed for a broad range of climate factors using a climate model designed for terrestrial-type exoplanets (Vladilo et al.\ 2015). After fixing the planetary data according to the experimental results (Jenkins et al.\ 2015), we changed the surface gravity, CO${}_2$ abundance, surface pressure, orbital eccentricity, rotation period, axis obliquity and ocean fraction within the range of validity of our model. For most choices of parameters we find habitable solutions with $h_{050}>0.2$ only for CO${}_2$ partial pressure $p_{\mathrm{C}{\mathrm{O}}_2}\lesssim 0.04$\,bar. At this limiting value of CO${}_2$ abundance the planet is still habitable if the total pressure is $p\lesssim 2$\,bar. In all cases the habitability drops for eccentricity $e\gtrsim 0.3$. Changes of rotation period and obliquity affect the habitability through their impact on the equator-pole temperature difference rather than on the mean global temperature. We calculated the variation of $h_{050}$ resulting from the luminosity evolution of the host star for a wide range of input parameters. Only a small combination of parameters yield habitability-weighted lifetimes $\gtrsim 2$\,Gyr, sufficiently long to develop atmospheric biosignatures still detectable at the present time.

arXiv comment15 pages, 6 figures, MNRAS accepted

References in corpus (34)

• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Habitable Zones Around Main-Sequence Stars: New Estimates
• The PLATO 2.0 Mission
• The false positive rate of Kepler and the occurrence of planets
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• Prevalence of Earth-size planets orbiting Sun-like stars
• Most 1.6 Earth-Radius Planets are not Rocky
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• The Occurrence Rate of Small Planets around Small Stars
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• The fast spin-rotation of a young extrasolar planet
• Increased insolation threshold for runaway greenhouse processes on Earth like planets
• The Habitability of Planets Orbiting M-dwarf Stars
• Exoplanet population inference and the abundance of Earth analogs from noisy, incomplete catalogs
• Exploring Exoplanet Populations with NASA's Kepler Mission
• Inevitability of Plate Tectonics on Super-Earths
• Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
• A Statistical Reconstruction of the Planet Population Around Kepler Solar-Type Stars
• Discovery and Validation of Kepler-452b: A 1.6-Re Super Earth Exoplanet in the Habitable Zone of a G2 Star
• Habitable Climates: The Influence of Obliquity
• Remote Life Detection Criteria, Habitable Zone Boundaries, and the Frequency of Earthlike Planets around M and Late-K Stars
• A Catalog of Kepler Habitable Zone Exoplanet Candidates
• The Kozai-Lidov Mechanism in Hydrodynamical Disks
• Atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters
• Occurrence and core-envelope structure of 1--4x Earth-size planets around Sun-like stars
• Climate Stability of Habitable Earth-like Planets
• Habitable Climates
• Terrestrial, Habitable-Zone Exoplanet Frequency from Kepler
• The habitable zone of Earth-like planets with different levels of atmospheric pressure
• CO2 condensation is a serious limit to the deglaciation of Earth-like planets
• Modeling the surface temperature of Earth-like planets
• Ultraviolet Observations of Super-Chandrasekhar Mass Type Ia Supernova Candidates with Swift UVOT
• From climate models to planetary habitability: temperature constraints for complex life
• Evidence of Significant Energy Input in the Late Phase of a Solar Flare from NuSTAR X-Ray Observations

Cited by in corpus (9)

• EOS-ESTM: A flexible climate model for habitable exoplanets
• Statistical properties of habitable zones in stellar binary systems
• EOS: Atmospheric Radiative Transfer in Habitable Worlds with HELIOS
• A rocky exoplanet classification method and its application to calculating surface pressure and surface temperature
• A novel metric for assessing climatological surface habitability
• Impact of vegetation albedo on the habitability of Earth-like exoplanets
• Interaction between vegetation and Snowball phases in the late Proterozoic Earth
• Assessing the Climate and Habitability of Tidally Locked Rocky Exoplanets
• A theoretical model for realistic local climates