Formation of satellites in circumplanetary discs generated by disc instability

Abstract

We investigated the formation and evolution of satellite systems in a cold, extended circumplanetary disc around a 10 MJupiter gas giant which was formed by gravitational instability at 50 AU from its star. The disc parameters were from a 3D global SPH simulation. We used a population synthesis approach, where we placed satellite embryos in this disc, and let them accrete mass, migrate, collide until the gaseous disc is dissipated. In each run we changed the initial dust-to-gas ratio, dispersion- and refilling time-scales within reasonable limits, as well as the number of embryos and their starting locations. We found that most satellites have mass similar to the Galilean ones, but very few can reach a maximum of 3 MEarth due to the massive circumplanetary disc. Large moons are often form as far as 0.5 Rdisc. The migration rate of satellites are fast, hence during the disc lifetime, an average of 10 MEarth worth of moons will be engulfed by the planet, increasing greatly its metallicity. We also investigated the effect of the planet’s semi-major axis on the resulting satellite systems by re-scaling our model. This test revealed that for the discs closer to the star, the formed moons are lighter, and a larger amount of satellites are lost into the planet due to the even faster migration. Finally, we checked the probability of detecting satellites like our population, which resulted in a low number of ≤ 3% even with upcoming powerful telescopes like E-ELT.

An exomoon survey of 70 cool giant exoplanets and the new candidate Kepler-1708 b-i

“…For a gaseous planet, the first scenario is unlikely to produce a debris disk massive enough to form a moon this large. The moon is also at the extreme end of the mass range produced by primordial disks in the traditional core-collapse picture of giant-planet formation [49][50][51] , but is easier in the case where planets form by disk instability 49,52 . Such models also naturally produce moons on low-inclination orbits.…”

AnN-body population synthesis framework for the formation of moons around Jupiter-like planets

“…Up to 20'000 simulations were run with different dust-to-gas ratios, disc life-times and timescales of dust refilling from the PPD, showing a great occurrence of sequential formation and massive satellites in this 1D limit. Similar models have been also implemented to study satellite formation around ice giants in the Solar System (Szulágyi et al 2018) and around Jupiter-like exoplanets that are forming with Gravitational Instability scenario resulting in significantly different CPD characteristics (Inderbitzi et al 2020).…”

On the Detection of Exomoons Transiting Isolated Planetary-mass Objects

“…The typical moon-to-planet mass fraction for large moons is observed to be approximately 2.5 × 10 −4 , which in theory is the result of the balance between the inflowing material and loss of material through orbital decay (Canup & Ward 2006). The N-body simulations have been used to study solar system moon formation and predict the demographics of exomoon systems (Ogihara & Ida 2012;Heller et al 2014;Heller 2016;Miguel & Ida 2016;Moraes et al 2018;Cilibrasi et al 2018Cilibrasi et al , 2021Ronnet & Johansen 2020;Inderbitzi et al 2020). In particular, Figure 3.…”

“…We have few observational constraints on the exomoon population (Hippke 2015;. However, there is an extensive and growing literature on the formation of moons around gas giants, including N-body simulations of moon formation via accretion in circumplanetary disks (Canup & Ward 2006;Ogihara & Ida 2012;Heller & Pudritz 2015a, 2015bMiguel & Ida 2016;Cilibrasi et al 2018Cilibrasi et al , 2021Moraes et al 2018;Inderbitzi et al 2020;Ronnet & Johansen 2020) and direct imaging of moon-forming disks (Benisty et al 2021). These studies suggest that moon formation around gas giants well separated from a host star is common and that the solar system moons are representative of moon formation around young, accreting giant planets.…”