2004/02/26 by Jonathan J. Fortney, W. B. Hubbard
Physics and Astronomy · #Astro and Planetary Science #Scientific Research and Discoveries #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/420765
published as Astrophys.J. 608 (2004) 1039-1049 · 22 pages, including 14 figures. Accepted to the Astrophysical Journal
arxiv created 2004/02/26 · openalex publication_date 2004/06/11 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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 0.15 M J -3.0 M J . 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 0.15 M J object and ~10 Gyr for a 3.0 M 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.