THE INNER EDGE OF THE HABITABLE ZONE FOR SYNCHRONOUSLY ROTATING PLANETS AROUND LOW-MASS STARS USING GENERAL CIRCULATION MODELS

By R. Kopparapu, E. Wolf, J. Haqq‐Misra, Jun Yang, J. Kasting, V. Meadows, R. Terrien, S. Mahadevan. 2016

161 citations recorded by the source corpus.

Terrestrial planets at the inner edge of the habitable zone (HZ) of late-K and M-dwarf stars are expected to be in synchronous rotation, as a consequence of strong tidal interactions with their host stars. Previous global climate model (GCM) studies have shown that, for slowly rotating planets, strong convection at the substellar point can create optically thick water clouds, increasing the planetary albedo, and thus stabilizing the climate against a thermal runaway. However these studies did not use self-consistent orbital/rotational periods for synchronously rotating planets placed at different distances from the host star. Here we provide new estimates of the inner edge of the HZ for synchronously rotating terrestrial planets around late-K and M-dwarf stars using a 3D Earth-analog GCM with self-consistent relationships between stellar metallicity, stellar effective temperature, and the planetary orbital/rotational period. We find that both atmospheric dynamics and the efficacy of the substellar cloud deck are sensitive to the precise rotation rate of the planet. Around mid-to-late M-dwarf stars with low metallicity, planetary rotation rates at the inner edge of the HZ become faster, and the inner edge of the HZ is farther away from the host stars than in previous GCM studies. For an Earth-sized planet, the dynamical regime of the substellar clouds begins to transition as the rotation rate approaches ∼10 days. These faster rotation rates produce stronger zonal winds that encircle the planet and smear the substellar clouds around it, lowering the planetary albedo, and causing the onset of the water-vapor greenhouse climatic instability to occur at up to ∼25% lower incident stellar fluxes than found in previous GCM studies. For mid-to-late M-dwarf stars with high metallicity and for mid-K to early-M stars, we agree with previous studies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/0110053dd0b1bc06ac8fefdd18c98ae3faa17c56

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Citations in the corpus

• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, background): “For a synchronized planet, we locate the inner edge at S p = 1.5 S ⊕ (the protection of the substellar point by clouds allows the planet to be much closer, e.g., Yang et al. 2013; Kopparapu et al. 2016).”
• The nature of the TRAPPIST-1 exoplanets. (2018, background): “Planet b however, is located beyond the runaway greenhouse limit for tidally locked planets (Kopparapu et al. 2016; Turbet et al. 2017) and could potentially reach – with a thick water vapour atmosphere – a surface temperature up to 2000 K (Kopparapu et al. 2013).”
• The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “However, these results have been shown to be sensitive to planetary orbital and rotational period, as well as stellar metallicity (Kopparapu et al., 2016).”
• How to Characterize Habitable Worlds and Signs of Life (2017, background): “…Edson et al. 2011, Zsom et al. 2012, Goldblatt et al. 2013, Leconte et al. 2013a,b, 2015, Vladilo et al. 2013, Wordsworth & Pierrehumbert 2014, Yang et al. 2013, 2014, Fereira et al. 2014, Wolf & Toon 2015, Linsenmeier et al. 2015, Kopparapu et al. 2016, Kitzmann 2017, Ramirez & Kaltenegger 2017).”
• Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model (2017, background): “…model version previously for studying a variety of Earth-like atmospheres (Wolf & Toon 2013, 2014a, 2014b, 2015; Wolf et al. 2017), and CAM4 has been frequently used elsewhere for studying slow rotating planets around M-dwarf stars (Yang et al. 2013, 2014; Kopparapu et al. 2016; Wang et al. 2016).”
• The habitability of Proxima Centauri b II. Possible climates and Observability (2016, background): “= 0.123 M ), defined as the range of orbital distances within which a planet can possibly maintain liquid water on its surface (Kasting et al. 1993; Kopparapu et al. 2013; Leconte et al. 2013a; Yang et al. 2013; Kopparapu et al. 2014, 2016).”
• Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets (2017, background): “The two inner planets of the system (TRAPPIST-1b and c) are likely too hot to sustain global oceans of liquid water (Kopparapu et al. 2013; Yang et al. 2013; Kopparapu et al. 2016).”
• Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs (2017, methodology): “The climates of these slowrotating worlds are strongly influenced by the circulation regime, as convection, clouds, and horizontal transport are fundamentally altered (Yang et al. 2013; Kopparapu et al. 2016).”
• How Hospitable Are Space Weather Affected Habitable Zones? The Role of Ion Escape (2017, unknown): “Recent detection of terrestrial-type exoplanets with approximately Earth sizes and masses within the climatological habitable zones ( CHZs ) provides the fi rst glimpse into the potential habitability of these worlds ( Kopparapu et al. 2016 ) .”