MINIMUM CORE MASSES FOR GIANT PLANET FORMATION WITH REALISTIC EQUATIONS OF STATE AND OPACITIES

Journal Article · Fri Feb 20 04:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/800/2/82· OSTI ID:22364178

Piso, Ana-Maria A.; Murray-Clay, Ruth A. ^[1]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

Giant planet formation by core accretion requires a core that is sufficiently massive to trigger runaway gas accretion in less than the typical lifetime of protoplanetary disks. We explore how the minimum required core mass, M {sub crit}, depends on a non-ideal equation of state (EOS) and on opacity changes due to grain growth across a range of stellocentric distances from 5-100 AU. This minimum M {sub crit} applies when planetesimal accretion does not substantially heat the atmosphere. Compared to an ideal gas polytrope, the inclusion of molecular hydrogen (H{sub 2}) dissociation and variable occupation of H{sub 2} rotational states increases M {sub crit}. Specifically, M {sub crit} increases by a factor of ∼2 if the H{sub 2} spin isomers, ortho- and parahydrogen, are in thermal equilibrium, and by a factor of ∼2-4 if the ortho-to-para ratio is fixed at 3:1. Lower opacities due to grain growth reduce M {sub crit}. For a standard disk model around a Solar mass star, we calculate M {sub crit} ∼ 8 M {sub ⊕} at 5 AU, decreasing to ∼5 M {sub ⊕} at 100 AU, for a realistic EOS with an equilibrium ortho-to-para ratio and for grain growth to centimeter-sizes. If grain coagulation is taken into account, M {sub crit} may further reduce by up to one order of magnitude. These results for the minimum critical core mass are useful for the interpretation of surveys that find exoplanets at a range of orbital distances.

• OSTI ID: 22364178
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 800; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
EQUATIONS OF STATE
GRAIN GROWTH
HYDROGEN
LIFETIME
MASS
OPACITY
PLANETS
PROTOPLANETS
ROTATIONAL STATES
SATELLITE ATMOSPHERES
SATELLITES
SPIN
STAR ACCRETION
STARS
THERMAL EQUILIBRIUM