TO COOL IS TO ACCRETE: ANALYTIC SCALINGS FOR NEBULAR ACCRETION OF PLANETARY ATMOSPHERES
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- 16 September 2015
- journal article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 811 (1), 41
- https://doi.org/10.1088/0004-637x/811/1/41
Abstract
Planets acquire atmospheres from their parent circumstellar disks. We derive a general analytic expression for how the atmospheric mass grows with time t as a function of the underlying core mass and nebular conditions, including the gas metallicity Z. Planets accrete as much gas as can cool: an atmosphere's doubling time is given by its Kelvin–Helmholtz time. Dusty atmospheres behave differently from atmospheres made dust-free by grain growth and sedimentation. The gas-to-core mass ratio (GCR) of a dusty atmosphere scales as GCR , where (for Z not too close to 1) is the mean molecular weight at the innermost radiative–convective boundary. This scaling applies across all orbital distances and nebular conditions for dusty atmospheres; their radiative–convective boundaries, which regulate cooling, are not set by the external environment, but rather by the internal microphysics of dust sublimation, H2 dissociation, and the formation of H−. By contrast, dust-free atmospheres have their radiative boundaries at temperatures close to nebular temperatures , and grow faster at larger orbital distances where cooler temperatures, and by extension lower opacities, prevail. At 0.1 AU in a gas-poor nebula, GCR , while beyond 1 AU in a gas-rich nebula, GCR . We confirm our analytic scalings against detailed numerical models for objects ranging in mass from Mars () to the most extreme super-Earths (10–), and explain why heating from planetesimal accretion cannot prevent the latter from undergoing runaway gas accretion.This publication has 32 references indexed in Scilit:
- GASEOUS MEAN OPACITIES FOR GIANT PLANET AND ULTRACOOL DWARF ATMOSPHERES OVER A RANGE OF METALLICITIES AND TEMPERATURESThe Astrophysical Journal Supplement Series, 2014
- THE MIGRATION OF GAP-OPENING PLANETS IS NOT LOCKED TO VISCOUS DISK EVOLUTIONThe Astrophysical Journal Letters, 2014
- ACCRETION AND EVOLUTION OF ∼2.5M⊕PLANETS WITH VOLUMINOUS H/He ENVELOPESThe Astrophysical Journal, 2014
- DENSITIES AND ECCENTRICITIES OF 139KEPLERPLANETS FROM TRANSIT TIME VARIATIONSThe Astrophysical Journal, 2014
- THREE-DIMENSIONAL RADIATION-HYDRODYNAMICS CALCULATIONS OF THE ENVELOPES OF YOUNG PLANETS EMBEDDED IN PROTOPLANETARY DISKSThe Astrophysical Journal, 2013
- THE FALSE POSITIVE RATE OFKEPLERAND THE OCCURRENCE OF PLANETSThe Astrophysical Journal, 2013
- Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to TransitsThe Astrophysical Journal, 2007
- Low‐Temperature OpacitiesThe Astrophysical Journal, 2005
- Planet Formation by Coagulation: A Focus on Uranus and NeptuneAnnual Review of Astronomy and Astrophysics, 2004
- Using FU Orionis outbursts to constrain self-regulated protostellar disk modelsThe Astrophysical Journal, 1994