Growth of Jupiter: Formation in disks of gas and solids and evolution to the present epoch

摘要

The formation of Jupiter is modeled via core-nucleated accretion, and the planet's evolution is simulated up to the present epoch. Throughout the phases when the planet acquires most of its heavy-element content, the calculation of solids' accretion accounts for interactions with an evolving disk of planetesimals. The phase of growth from an embryo of a few hundred kilometers in radius until the time when the accretion of gas overtakes solids' accretion was presented by D'Angelo et al. (2014), and the same numerical methods are applied here. Those calculations followed the formation for about 4 x 10(5) years, until the epoch when the heavy-element and hydrogen/helium masses were M-z approximate to 7.3 and M-XY approximate to 0.15 Earth's masses (M-circle plus), respectively, and (M) over dot(XY) approximate to (M) over dot(Z). Herein, the calculation is continued through the phase when M-XY grows to equal M-Z, at which age, about 2.4 x 10(6) years, the total mass of the planet is M-p approximate to 20 M-circle plus. About 9 x 10(5) years later, M-p is approximately 60 M-circle plus and M-Z approximate to 16 M-circle plus, three-quarters of which are delivered by planetesimals larger than 10km in radius. Around this epoch, the contraction of the envelope dictates gas accretion rates a few times 10(-3) M-circle plus per year, initiating the regime of disk-limited accretion, whereby the planet can accrete all the gas provided by the disk, and its evolution is therefore tied to disk's evolution. Growth is continued by constructing simplified models of protosolar accretion disks that evolve through viscous diffusion, winds, and accretion on the planet. Jupiter's formation ends after approximate to 3.4-4.2 Myr, depending on the applied disk viscosity parameter, when nebula gas disperses. The young Jupiter is 4.5-5.5 times as voluminous as it is presently and thousands of times as luminous, similar to 10(-5) L-circle dot. The heavy-element mass is approximate to 20 M-circle plus. The evolution proceeds through the cooling and contraction phase, in isolation except for solar irradiation. After 4570 Myr, the age of the solar system, radius and luminosity of the planet are within 10% of current values, accounting also for uncertainties in the power absorbed from the Sun. During formation, and soon thereafter, the planet exhibits features, e.g., luminosity and effective temperature, that may probe aspects of the latter stages of formation, if observable. These possibly distinctive features, however, seem to disappear within a few tens of Myr