This is the case, for example, for the satellites of Jupiter and Saturn. If multiple objects orbit the primary, and the orbiting objects occupy a mean motion resonance, periodic gravitational perturbations will help maintain non-zero eccentricities. For a single secondary object, that is, a lone moon orbiting a planet, or a lone planet orbiting a star, tidal dissipation rapidly decreases the orbital eccentricity of the secondary, and then ceases when e = 0 ( Murray & Dermott 1999). Here, tidal dissipation (or tidal heating) refers to the process of the dissipation of orbital energy in the interior of a solid body (a moon or a planet). 2009) and could significantly enhance the habitable volume in the galaxy by warming exoplanets and their satellites (exomoons) ( Dobos & Turner 2015). Tidal heating is an important energy source in the satellites of the outer planets in our solar system (e.g., McEwen et al. 2017), so that the tidal forces on the bodies vary with time, resulting in heating of their interiors by tidal dissipation ( Luger et al. The planets also have non-zero orbital eccentricities ( Gillon et al. Given the planets’ mean densities, these low temperatures suggest that some might have solid surfaces composed of H 2O ice and/or rock. Given their proximity to the star, and the star’s low mass and luminosity, the surface of each planet has a moderate temperature, ranging from ~160 to 400 K ( Gillon et al. The planets orbit the star with semi-major axes <0.1 AU, and orbital periods of a few Earth days. 2017) has vaulted this system to the forefront of exoplanetary characterization. The recent discovery of seven roughly Earth-sized planets orbiting the low-mass star TRAPPIST-1 ( Gillon et al. Key words: astrobiology / methods: numerical / planets and satellites: general / planets and satellites: interiors Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers. Determining the planet’s masses within ~0.1–0.5 Earth masses would confirm or rule out the presence of H 2O and/or iron. Planet d avoids the runaway greenhouse state if its albedo is ≳0.3. Planets d and e are the most likely to be habitable. Tidal heat fluxes on planets d, e, and f are twenty times higher than Earth’s mean heat flow.Ĭonclusions. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles planet c may have surface eruptions of silicate magma, potentially detectable with next-generation instrumentation. With the exception of TRAPPIST-1c, all have densities low enough to indicate the presence of significant H 2O. The compositions for planets b, c, d, and e remain uncertain given the error bars on mass and radius. We also construct a tidal heat generation model using a single uniform viscosity and rigidity based on each planet’s composition. Assuming the planets are composed of uniform-density noncompressible materials (iron, rock, H 2O), we determine possible compositional models and interior structures for each planet. We also aim to determine the precision in mass and radius necessary to determine the planets’ compositions. We aim to determine interior structures for each planet and estimate the temperatures of their rock mantles due to a balance between tidal heating and convective heat transport to assess their habitability. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf.Īims. With seven planets, the TRAPPIST-1 system has among the largest number of exoplanets discovered in a single system so far. Sydney Institute for Astronomy, School of Physics A28, University of Sydney,Ĭontext. Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences,ĮLTE Eötvös Loránd University, Gothard Astrophysical Observatory, Szombathely, Kiss 2 ,5Į-mail: Thege Miklós Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Astronomical objects: linking to databasesĪmy C.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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