Minor Planet Center Confirms 117 Moons for Saturn

The Minor Planet Center has confirmed the addition of 28 newly discovered moons of Saturn. Saturn now has 117 moons and Jupiter has 95.

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.

List of confirmed moons of Saturn.

5 thoughts on “Minor Planet Center Confirms 117 Moons for Saturn”

  1. “Moon”, like “planet”, isn’t a natural category. And never mind that nonsense about orbit clearing they used as an excuse to get edgy and demote Pluto.

    I suggest that “planet” be used for any object orbiting a star which is large enough that gravity determines its over-all shape, and “moon” for any such object orbiting a “planet”. When the bodies are close enough in mass that the center of mass for them is outside of either, they both get to be “planets”.

    Everything else can be called an asteroid or comet, depending on perhaps how elliptical the orbit is. Objects that are too small to have gravity dictate their shape, but which orbit a planet or moon, we can call “captured” asteroids.

    By this standard, of course, “the Moon” IS a moon. Phobos and Demos are just captured asteroids, along with most of Saturn’s ‘moons’. Both Pluto and Ceres get to be planets.

    • So then Mimas is the smallest round moon at about 246 miles across. Interestingly the Death Star was 100 miles across. So the “that’s no moon” but it was round is the correct identification (aka not a moon). Hyperion has a potato shape. Hyperion’s mean radius is 83.9 miles (135 kilometers), but since Hyperion is rather potato-shaped, its shape can be described in terms of its diameter along its three axes: 255 x 163 x 137 miles (410 x 260 x 220 kilometers, respectively).

  2. What is a moon?
    Just a word without scientific significance. Probably a futile exercise to try and define moon as something scientifically meaningful. Everything is just chunks of matter interacting with other chunks of matter over time. They split, merge, change orbits, evaporate, change composition, get mined, get turned into giant space ships, etc. until the universe recycles. It all changes and no matter what properties we try to use to define a moon, it won’t work for long. Why even try?

    There are too many to give them personal unique names and it will get exponentially worse the farther out we map space. Just use existing names for the already discovered big bodies to make it easier to communicate in human language. Then create an official catalog of the trillion other objects. The catalog/database can keeps track of all known (but changing) properties and also relative to positions in space-time. Then everything at least gets an index number that can be referred to and looked up quickly with a simple online app.

    • Sure, but if these labels are insignificant, then people wouldn’t get so worked up about Pluto not being called one anymore. The actual point of the planet definition was to try and get a lock on what is an exoplanet, and what is a member of an exo-asteroid belt. In the same vein, while we are still a ways away from detecting exomoons, perhaps a definition will let us get a head start on the cataloguing of satellites in remote stellar systems.

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