Habitable planets around the star Gliese 581

By F. Selsis, J. Kasting, B. Levrard, J. Paillet, I. Ribas, X. Delfosse. 2007

450 citations recorded by the source corpus.

Radial velocity surveys are now able to detect terrestrial planets at habitable distance from M-type stars. Recently, two planets with minimum masses below 10 Earth masses were reported in a triple system around the M-type star Gliese 581. Using results from atmospheric models and constraints from the evolution of Venus and Mars, we assess the habitability of planets Gl 581c and Gl 581d and we discuss the uncertainties affecting the habitable zone (HZ) boundaries determination. We provide simplified formulae to estimate the HZ limits that may be used to evaluate the astrobiological potential of terrestrial exoplanets that will hopefully be discovered in the near future. Planets Gl 581c and 'd' are near, but outside, what can be considered as the conservative HZ. Planet 'c' receives 30% more energy from its star than Venus from the Sun, with an increased radiative forcing caused by the spectral energy distribution of Gl 581. Its habitability cannot however be positively ruled out by theoretical models due to uncertainties affecting cloud properties. Irradiation conditions of planet 'd' are comparable with those of early Mars. Thanks to the warming effect of CO2-ice clouds planet 'd' might be a better candidate for the first exoplanet known to be potentially habitable. A mixture of various greenhouse gases could also maintain habitable conditions on this planet.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/96eec2ad257612ba75373f9b9f33d8433f1a06f5

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Citations in the corpus

• HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: DEPENDENCE ON PLANETARY MASS (2014, background): “Accordingly, the circumstellar HZ is defined as the region around which a terrestrial mass planet, with favorable atmospheric conditions, can sustain liquid water on its surface (Huang 1959; Hart 1978; Kasting et al. 1993; Selsis et al. 2007b; Kopparapu et al. 2013).”
• The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “This lower planetary Albedo may allow M-dwarf planets to absorb more instellation from their host stars, increasing their global mean surface temperature (Kasting et al., 1993; Selsis et al., 2007; Shields et al., 2013, 2014; von Paris et al., 2013).”
• PLANETARY CANDIDATES OBSERVED BY KEPLER. III. ANALYSIS OF THE FIRST 16 MONTHS OF DATA (2012, background): “Recent modeling efforts suggest that the equilibrium temperature at the inner edge of the HZ might be closer to 270 K (Selsis et al. 2007), corresponding to rapid water loss via H escape or a runaway greenhouse effect, depending on the surface water content.”
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, methodology): “The mass loss is given by (Lammer et al. 2003; Selsis et al. 2007a): ṁ = FXUVπRp3 GMp(a/1AU)2 , (9) where a is the planet’s semi-major axis, Rp its radius and Mp its mass. is the fraction of the incoming energy that is transferred into gravitational energy through the mass loss.”
• TERRESTRIAL PLANET OCCURRENCE RATES FOR THE KEPLER GK DWARF SAMPLE (2015, background): “…occurrence rates in terms of Porb such as ζ, has advantages over providing occurrence rates in terms of stellar insolation flux, such as the Venus zone (η♀) concept of Kane et al. (2014) or the HZ (η⊕) concept (Kasting et al. 1993; Selsis et al. 2007; Zsom et al. 2013; Kopparapu et al. 2013).”
• PLANETARY CANDIDATES OBSERVED BY KEPLER IV: PLANET SAMPLE FROM Q1–Q8 (22 MONTHS) (2013, methodology): “Specifying the boundary of the HZ to support anthropocentrist life is an active area of research (Selsis et al. 2007; Kasting 2011; Kopparapu et al. 2013; Zsom et al. 2013).”
• Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1 (2016, methodology): “Earth-like planets have been detected in the HZs (defined in Kasting, Whitmire, & Reynolds 1993; Selsis et al. 2007a; Kopparapu et al. 2013) of early type M-dwarfs (e.g., Quintana et al. 2014).”
• A REVISED ESTIMATE OF THE OCCURRENCE RATE OF TERRESTRIAL PLANETS IN THE HABITABLE ZONES AROUND KEPLER M-DWARFS (2013, methodology): “Several other studies (Underwood et al. 2003; Selsis et al. 2007b) parametrized Kasting et al. (1993) results to estimate relationships between HZ boundaries and stellar parameters for stars of different spectral types.”
• THE ULTRAVIOLET RADIATION ENVIRONMENT AROUND M DWARF EXOPLANET HOST STARS (2012, background): “It is estimated to have an age of 8 ± 1 Gyr (Selsis et al. 2007) and a somewhat subsolar metallicity, [Fe/H] = −0.10 – −0.02 (Johnson & Apps 2009; Rojas-Ayala et al. 2010).”
• 3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability and habitability (2013, methodology): “If a given target’s 12 This estimation differs from the one of Selsis et al. (2007) because they used an eccentricity of 0.16 as initially found by Udry et al. (2007). flux is too small to use spectroscopy, broad band photometry (as done for Kepler-10 b (Batalha et al. 2011) and CoRoT-7 b (Léger et…”
• THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS (2013, methodology): “…Teff ≤ 7200K because Kasting et al. (1993) calculated the boundaries of the habitable zone for stars with temperatures of 3700K, 5700K, and 7200K. Selsis et al. (2007) deals with the lower temperature limit by assuming that the albedo of a habitable planet orbiting a star with a temperature…”
• THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, background): “It is estimated to have an age of 5.6 ± 0.1 Gyr and a subsolar metallicity, [Fe/H] = −0.26 (Tsantaki et al. 2013), based on its 47 day rotation period.”
• Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model (2017, methodology): “…in mind, we conduct 3D climate calculations for planets in the TRAPPIST-1 system assuming atmospheres composed of N2, CO2, and H2O, following the traditional assumptions for terrestrial planetary atmospheres within the habitable zone (Kasting et al. 1993; Selsis et al. 2007; Kopparapu et al. 2013).”
• A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone (2013, background): “Traditionally, analyses of planetary habitability begin with determining if a planet is in the habitable zone (Dole 1964; Hart 1979; Kasting et al. 1993; Selsis et al. 2007; Kopparapu et al. 2013), but many factors are relevant.”
• How to Characterize Habitable Worlds and Signs of Life (2017, methodology): “…several teams have shown that oxygen can build up abiotically under certain geological settings (e.g., Schindler & Kasting 2000, Segura et al. 2007, Selsis et al. 2007, Leger et al. 2011, Hu et al. 2012, Wordsworth & Pierrehumbert 2013, Harman et al. 2015, Tian et al. 2014, Luger & Barnes 2015,…”
• The HARPS search for southern extra-solar planets - XXXI. The M-dwarf sample (2011, methodology): “For more detailed considerations, we refer the reader to more comprehensive models (e.g. Selsis et al. 2007).”
• The HARPS search for Earth-like planets in the habitable zone - I. Very low-mass planets around HD 20794, HD 85512, and HD 192310 (2011, background): “HARPS also revealed to us the system Gl 581, with two possibly rocky planets c and d with masses of 5 and 8 MEarth, respectively, both lying at the edge of the habitable zone (HZ) of their parent star (Udry et al. 2007; Selsis et al. 2007), and the Gl 581 e of only 1.9 M⊕ (Mayor et al. 2009a).”
• THE OCCURRENCE OF POTENTIALLY HABITABLE PLANETS ORBITING M DWARFS ESTIMATED FROM THE FULL KEPLER DATASET AND AN EMPIRICAL MEASUREMENT OF THE DETECTION SENSITIVITY (2015, background): “Even for non-tidally-locked planets, the presence of clouds can expand the distances corresponding to the boundaries of the habitable zone by roughly 40% depending on the degree of cloud cover (Selsis et al. 2007).”
• A FRAMEWORK FOR QUANTIFYING THE DEGENERACIES OF EXOPLANET INTERIOR COMPOSITIONS (2009, background): “It is conventional to accept that accretion of nebula gases is most important for massive protoplanetary cores; accretion of nebular gas is expected for rocky cores above 10 M⊕ while often neglected for planets below 6 M⊕ (e.g. Selsis et al. 2007a).”
• STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS (2013, background): “Water clouds would therefore have a weak greenhouse effect in this regime (Kasting 1988), but may significantly increase planetary albedo (Selsis et al. 2007; Kaltenegger et al. 2011).”