Effects of helium phase separation on the evolution of extrasolar giant planets

Jonathan J. Fortney, William B. Hubbard

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

We build on recent new evolutionary models of Jupiter and Saturn and here extend our calculations to investigate the evolution of extrasolar giant planets of mass 0.15MJ-3.0MJ. Our inhomogeneous thermal history models show that the possible phase separation of helium from liquid metallic hydrogen in the deep interiors of these planets can lead to luminosities ∼2 times greater than have been predicted by homogeneous models. For our chosen phase diagram this phase separation will begin to affect the planets' evolution at ∼700 Myr for a 0.15MJ object and ∼10 Gyr for a 3.0M J object. We show how phase separation affects the luminosity, effective temperature, radii, and atmospheric helium mass fraction as a function of age for planets of various masses, with and without heavy element cores, and with and without the effect of modest stellar irradiation. This phase separation process will likely not affect giant planets within a few AU of their parent star, as these planets cool to their equilibrium temperatures, determined by stellar heating, before the onset of phase separation. We discuss the detectability of these objects and the likelihood that the energy provided by helium phase separation can change the timescales for formation and settling of ammonia clouds by several gigayears. We discuss how correctly incorporating stellar irradiation into giant planet atmosphere and albedo modeling may lead to a consistent evolutionary history for Jupiter and Saturn.

Original languageEnglish (US)
Pages (from-to)1039-1049
Number of pages11
JournalAstrophysical Journal
Volume608
Issue number2 I
DOIs
StatePublished - Jun 20 2004

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helium
planets
planet
Saturn
Jupiter (planet)
Jupiter
irradiation
luminosity
metallic hydrogen
histories
liquid hydrogen
settling
heavy elements
history
effect
albedo
ammonia
temperature
diagram
phase diagrams

Keywords

  • Equation of state
  • Planetary systems
  • Planets and satellites: general
  • Planets and satellites: individual (Jupiter, Saturn)

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Effects of helium phase separation on the evolution of extrasolar giant planets. / Fortney, Jonathan J.; Hubbard, William B.

In: Astrophysical Journal, Vol. 608, No. 2 I, 20.06.2004, p. 1039-1049.

Research output: Contribution to journalArticle

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