National Astronomical Observatory of Japan | 2020 Mar 09
Numerical simulations showed that the temperature gradient in the disk of gas around a young gas giant planet could play a critical role in the development of a satellite system dominated by a single large moon, similar to Titan around Saturn. Researchers found that dust in the circumplanetary disk can create a “safety zone,” which keeps the moon from falling into the planet as the system evolves.An artist’s impression of a satellite forming around a giant gas planet
which is itself still forming around a star. (Credit: Nagoya University)
Astronomers believe that many of the moons we see in the Solar System, especially large moons, formed along with the parent planet. In this scenario, moons form from the gas and dust spinning around the still forming planet. But previous simulations have resulted in either all large moons falling into the planet and being swallowed-up or in multiple large moons remaining. The situation we observe around Saturn, with many small moons but only one large moon, does not fit in either of these models.
Yuri Fujii ... and Masahiro Ogihara ... created a new model of circumplanetary disks with a more realistic temperature distribution by considering multiple sources of opacities including dust and ice. Then, they simulated the orbital migration of moons considering pressure from disk gas and the gravity of other satellites.
Their simulations show that there is a “safety zone” where a moon is pushed away from the planet. In this area, warmer gas inside the orbit pushes the satellite outward and prevents it from falling into the planet. ...
Formation of Single-Moon Systems Around Gas Giants ~ Yuri I. Fujii, Masahiro Ogihara
- Astronomy & Astrophysics 635:L4 (Mar 2020) DOI: 10.1051/0004-6361/201937192