Heat Transport in Giant (Exo)planets: A New Perspective

By G. Chabrier, Isabelle Baraffe. 2007

162 citations recorded by the source corpus.

We explore the possibility that large-scale convection is inhibited over some regions of giant planet interiors, as a consequence of a gradient of composition inherited from either their formation history or particular events like giant impacts or core erosion during their evolution. Under appropriate circumstances, the redistribution of the gradient of molecular weight can lead to double diffusive layered or overstable convection. This leads to much less efficient heat transport and compositional mixing than large-scale adiabatic convection. We show that this process can explain the abnormally large radius of the transit planet HD 209458b and similar objects and may be at play in some giant planets, with short-period planets offering the most favorable conditions. Observational signatures of this transport mechanism are a large radius and a reduced heat flux output compared with uniformly mixed objects. If our suggestion is correct, it bears major consequences on our understanding of giant planet formation, structure and evolution, including possibly our own Jovian planets.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/6d56474f43175dca29eada7e809a469f30baebdb

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In Astronomy and Astrophysics

1. Jon Fortney
2. C. Mordasini
3. Sara Seager
4. N. Madhusudhan
5. M. Marley
6. Th. Henning
7. D. Charbonneau
8. E. Lopez

Citations in the corpus

• Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core (2017, background): “The formation of a compositional gradient could lead to double-diffusive convection [Chabrier and Baraffe, 2007; Leconte and Chabrier, 2013] in Jupiter’s deep interior, which could lead to a slow redistribution of heavy elements, even on planetary evolution timescales.”
• A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres (2007, background): “Independent of Tint, which could in principle be affected by barriers to convection (Stevenson 1985; Chabrier & Baraffe 2007), the higher the entropy of the interior adiabat, the warmer the atmospheric adiabat, the larger the radius of the planet, and the less likely the deep atmosphere profile at…”
• AB INITIO SIMULATIONS FOR MATERIAL PROPERTIES ALONG THE JUPITER ADIABAT (2012, background): “Lastly, while standard giant planet models assume an adiabatic, convective interior, the high thermal diffusivity together with a possible presence of a compositional gradient might suppress large-scale convection (Chabrier & Baraffe 2007; Leconte & Chabrier 2012).”
• THE MASS–METALLICITY RELATION FOR GIANT PLANETS (2015, background): “Such a model implies that cooler giants could be “anomalously” inflated if they have the right compositional structure (Chabrier & Baraffe 2007), but no such planets have been observed.”
• Characterization of exoplanets from their formation - I. Models of combined planet formation and evolution (2012, background): “In reality (Stevenson 1985; Chabrier & Baraffe 2007), it is possible that compositional gradients exist, originating, for example, from the dissolution of the core (Wilson & Militzer 2012) or the destruction of planetesimals in deeper layers (Mordasini et al. 2005).”
• New Models of Jupiter in the Context of Juno and Galileo (2019, background): “…Chabrier (2012), Leconte and Chabrier (2013)), whether such structures can persist during Jupiter’s, or in fact any gaseous planet cooling history (Chabrier and Baraffe, 2007) needs to be explored with extreme care (e.g. Rosenblum et al. (2011), Mirouh et al. (2012), Wood et al. (2013),…”
• WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, background): “…(Showman & Guillot 2002), enhanced atmospheric opacities (Burrows et al. 2007), reduced heat transport efficiency by layered convection inside the planets (Chabrier & Baraffe 2007), or Ohmic heating from currents induced through winds in the planetary atmospheres (Batygin & Stevenson 2010).”
• Two Classes of Hot Jupiters (2007, background): “Most models for the anomalous radius of HD209458b and other extrasolar planets postulate an extra source of energy of some kind (e.g., Bodenheimer et al. 2001; Showman & Guillot 2002; Winn & Holman 2005) or a way to retard the cooling more than normal (Chabrier & Baraffe 2007).”
• Is tidal heating sufficient to explain bloated exoplanets? Consistent calculations accounting for finite initial eccentricity (2010, background): “…and thus reach- ing deep enough layers to affect the planet’s inner isentrope, or inefficient large-scale convection due to a composition gradient (Chabrier & Baraffe 2007) could be the other mechanisms to be considered with tidal dissipation to lead eventually to these large planet radii (see…”
• A new vision of giant planet interiors: Impact of double diffusive convection (2012, background): “As discussed in Chabrier & Baraffe (2007), since the convective plumes must be fed by the diffusive interfaces, the thermal convective (N−1T ) and diffusive (δ 2 T /κT ) time scales should be similar in each respective layer.”
• Ab Initio Equation of State Data for Hydrogen, Helium, and Water and the Internal Structure of Jupiter (2007, background): “Further evolution of the planet may include erosion of core material (Chabrier & Baraffe 2007; Guillot et al. 2003) and homogeneous redistribution of destroyed planetesimals due to convection (Kerley 2004a).”
• Transits and Occultations (2010, background): “…constituents that efficiently trap internal heat (Burrows et al. 2007); enhanced downward convection allowing the incident stellar radiation to reach significant depth (Guillot & Showman 2002); and inhibition of convection within the planet that raps internal heat (Chabrier & Baraffe 2007).”
• LACK OF INFLATED RADII FOR KEPLER GIANT PLANET CANDIDATES RECEIVING MODEST STELLAR IRRADIATION (2011, background): “Layered convection should occur in atmospheres characterized by molecular weight gradients (Chabrier & Baraffe 2007).”
• THE MASS OF KOI-94d AND A RELATION FOR PLANET RADIUS, MASS, AND INCIDENT FLUX (2013, background): “For completeness, we mention that delayed planetary contraction, due either to higher than anticipated atmospheric opacities (Burrows et al. 2007) or interior barrier to convection (Chabrier & Baraffe 2007) are another class of solutions which could contribute somewhat to larger radii.”
• The Interior Structure, Composition, and Evolution of Giant Planets (2009, background): “– Chabrier & Baraffe (2007), independently following along the lines of a hypothesis from Stevenson (1985), suggest that gradients in heavy elements (such as from core dredge-up or dissolution of planetesimals) could suppress convection and cooling in the H/He envelope, leading to large radii at…”