Single-Moon Systems Possible around Gas-Giant Planets | Astronomy – Sci-News.com
A team of astronomers in Japan has demonstrated that systems can form that have only one large moon, such as Titan around Saturn, around a gas giant.
An artist’s impression of several moons forming around a young gas-giant planet. Image credit: Nagoya University.
“Many of the moons we see in the Solar System, especially large moons, formed along with the parent planet,” said Nagoya University’s Dr. Yuri Fujii and Dr. Masahiro Ogihara from the National Astronomical Observatory of Japan.
“In this scenario, moons form from the gas and dust spinning around the still forming planet.”
“But previous simulations 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.”
In the new study, the researchers created a novel model of circumplanetary disks with a more realistic temperature distribution.
They simulated the orbital migration of moons, taking in to consideration a pressure from disk gas and the gravity of other satellites.
They found that dust in the circumplanetary disk can create a ‘safety zone’ where a moon is pushed away from the giant planet.
In this zone, warmer gas inside the orbit pushes the satellite outward and prevents it from falling into the planet.
“We demonstrated for the first time that a system with only one large moon around a giant planet can form,” Dr. Fujii said.
“This is an important milestone to understand the origin of Titan.”
“It would be difficult to examine whether Titan actually experienced this process,” Dr. Ogihara added.
“Our scenario could be verified through research of satellites around extrasolar planets.”
“If many single-exomoon systems are found, the formation mechanisms of such systems will become a red-hot issue.”
The findings were published in the journal Astronomy & Astrophysics.
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Yuri I. Fujii & Masahiro Ogihara. 2020. Formation of single-moon systems around gas giants. A&A 635, L4; doi: 10.1051/0004-6361/201937192
