A Decreased Probability of Habitable Planet Formation around Low-Mass Stars

By S. Raymond, J. Scalo, V. Meadows. 2007

159 citations recorded by the source corpus.

Smaller terrestrial planets (≲0.3 M⊕) are less likely to retain the substantial atmospheres and ongoing tectonic activity probably required to support life. A key element in determining whether sufficiently massive sustainably habitable planets can form is the availability of solid planet-forming material. We use dynamical simulations of terrestrial planet formation from planetary embryos and simple scaling arguments to explore the implications of correlations between terrestrial planet mass, disk mass, and the mass of the parent star. We assume that the protoplanetary disk mass scales with stellar mass as Mdisk ∝ fM, where f measures the relative disk mass and 1/2 < h < 2, so that disk mass decreases with decreasing stellar mass. We consider systems without Jovian planets, based on current models and observations for M stars. We assume the mass of a planet formed in some annulus of a disk with given parameters is proportional to the disk mass in that annulus and show with a suite of simulations of late-stage accretion that the adopted prescription is surprisingly accurate. Our results suggest that the fraction of systems with sufficient disk mass to form >0.3 M⊕ habitable planets decreases for low-mass stars for every realistic combination of parameters. This habitable fraction is small for stellar masses below a mass in the interval 0.5-0.8 M☉, depending on disk parameters, an interval that excludes most M stars. Radial mixing and therefore water delivery are inefficient in the lower mass disks commonly found around low-mass stars, such that terrestrial planets in the habitable zones of most low-mass stars are likely to be small and dry.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/36682c39e47efb28d1e31dba43d3c4b29a376c76

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Citations in the corpus

• Debris disks as signposts of terrestrial planet formation (2011, background): “…between the dust mass and the stellar mass such that the typical protoplanetary disk contains a few percent of the stellar mass (Andrews & Williams 2007a), which has important implications for the planet frequency as a function of stellar mass (Ida & Lin 2005; Raymond et al. 2007; Greaves 2010).”
• How to Characterize Habitable Worlds and Signs of Life (2017, background): “This was attributed either to higher orbital speeds, leading to more energetic collisions with other bodies (Lissauer 2007), or to starting out dry because of inefficient radial mixing, and so fewer volatile-rich planetesimals from greater distances would be accreted (Raymond et al. 2007).”
• The Cosmic Shoreline: The Evidence that Escape Determines which Planets Have Atmospheres, and what this May Mean for Proxima Centauri B (2017, background): “It is apparent at a glance that Proxima b is more vulnerable to the negative consequences of impacts than are Earth and Venus, a not surprising observation that has been anticipated (cf, Raymond et al. 2007; Lissauer 2007).”
• The nature of the TRAPPIST-1 exoplanets. (2018, background): “…water contents, such as desiccation of constituent planetesimals by short-lived radionuclides (Grimm & McSween 1993), water loss during giant impacts between embryos (Genda & Abe 2005), and heating during the very rapid growth expected around low-mass stars (Lissauer 2007; Raymond et al. 2007).”
• The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “Given the recent results suggesting that habitable-zone M-dwarf planets may be dry—either due to low protostellar disk mass (Raymond et al., 2007), or extended XUV radiation input over as long as 1 Gyr (Luger & Barnes, 2015)—and land planets are both less likely to have saturated atmospheres prone…”
• THE INNER EDGE OF THE HABITABLE ZONE FOR SYNCHRONOUSLY ROTATING PLANETS AROUND LOW-MASS STARS USING GENERAL CIRCULATION MODELS (2016, background): “Several studies have argued that terrestrial planets within the HZs of M dwarfs may not be habitable, either because they could be deficient in volatiles (Lissauer 2007) or form dry as a result of inefficient water delivery (Raymond et al. 2007), if they formed in situ.”
• A STELLAR-MASS-DEPENDENT DROP IN PLANET OCCURRENCE RATES (2014, background): “It may be an imprint of a different formation efficiency of planets around low-mass stars, for example, the formation of more numerous, but smaller planets (e.g., Kokubo et al. 2006; Raymond et al. 2007).”
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, background): “The loss of hydrogen does not significantly change when considering different initial time of protoplanetary disk dispersion (3 or 10 Myr here).”
• A STEEPER THAN LINEAR DISK MASS–STELLAR MASS SCALING RELATION (2016, background): “Indeed, planet formation models find that the disk mass strongly impacts the frequency and location of planets that can form, from giants down to Earth-sized planets (e.g., Raymond et al. 2007; Alibert et al. 2011; Mordasini et al. 2012).”
• A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone (2013, background): “Models of rocky planet formation around M dwarfs have found that those that accrete from primordial material are likely to be sub-Earth mass (Raymond et al. 2007) and volatilepoor (Lissauer 2007).”