A Fragmented Firmament: An In-Depth Look at the Moons of Saturn

Monday - May 15 2023, 02:09 UTC - 1 year ago

This article provides an in-depth look into the moons of Saturn. 24 of Saturn's moons have regular orbits around it, while the remaining 100 are irregular with high inclinations and are most likely captured minor planets. Saturn's rings are filled with an unknown number of moonlets, some that have been discovered, and some that haven't. This fragmented firmament is always changing with the possibility of more moons and objects being discovered.

Corey Powell notes that if we start counting all the chunks in the rings, the number could go into the thousands…or the trillions.

Maybe it’s time for a formal definition of “What is a moon?” .

There are a couple of hundred candidate moons for Jupiter and for Saturn, which are being gradually confirmed. Similarly small satellites of Uranus and Neptune are harder to find.

Twenty-four of Saturn’s moons are regular satellites; they have prograde orbits not greatly inclined to Saturn’s equatorial plane. They include the seven major satellites, four small moons that exist in a trojan orbit with larger moons, two mutually co-orbital moons, and two moons that act as shepherds of Saturn’s narrow F Ring. Two other known regular satellites orbit within gaps in Saturn’s rings. The relatively large Hyperion is locked in an orbital resonance with Titan. The remaining regular moons orbit near the outer edge of the dense A Ring, within the diffuse G Ring, and between the major moons Mimas and Enceladus. The regular satellites are traditionally named after Titans and Titanesses or other figures associated with the mythological Saturn.

The remaining 100, with mean diameters ranging from 2 to 213 km (1 to 132 mi), are irregular satellites, whose orbits are much farther from Saturn, have high inclinations, and are mixed between prograde and retrograde. These moons are probably captured minor planets, or fragments from the collisional breakup of such bodies after they were captured, creating collisional families. Saturn is expected to have around 150 irregular satellites larger than 2.8 km (1.7 mi) in diameter, plus many hundreds more that are even smaller.

The rings of Saturn are made up of objects ranging in size from microscopic to moonlets hundreds of meters across, each in its own orbit around Saturn. There is no objective boundary between the countless small anonymous objects that form Saturn’s ring system and the larger objects that have been named as moons. Over 150 moonlets embedded in the rings have been detected by the disturbance they create in the surrounding ring material, though this is thought to be only a small sample of the total population of such objects.

There are 60 unnamed moons beyond the rings all irregular. If named, most will receive names from Gallic, Norse and Inuit mythology based on the orbital group they are a member of. These groups, as well as the 24 moons that have one or more regular orbits, form a fragmented firmament in our Solar System; one full of intrigue, beauty and possibilities worthy of deeper exploration. The universe of Saturn's moons is always changing, with the continuous discovery of new moons and the possibility of new moonlets hidden within the rings themselves. In the end, we have the unique opportunity to observe some of the objects which most influenced our understanding of the universe, and which form a sui generis landscape of knowledge.