Astronomers Thought They Had Counted All of Saturn’s Moons. After Studying Them for a Year, They Received Quite a Surprise

Saturn didn’t need more moons to be a beautiful planet, but it certainly has plenty. A team of astronomers has increased the official count to 274, almost twice as many as all the other planets’ moons combined.

Jupiter stays behind. In early 2023, Saturn overtook Jupiter to claim the title of the “planet with the most moons.” Researchers had discovered 62 new satellites, bringing its total to 145. At that time, astronomers suspected that more faint satellites were still orbiting Saturn.

Observations made with the Canada-France-Hawaii Telescope from 2019 to 2021 hinted at these additional moons. The challenge was to accurately connect each point of light (potential moons) through various images to confirm they were the same object with a stable orbit.

128 new moons. Throughout 2023, a team led by Taiwan’s Academia Sinica Institute of Astronomy and Astrophysics continued to investigate these signals with further observations.

Researchers ultimately gathered enough evidence to designate 128 new moons, which the International Astronomical Union (IAU) officially recognized on Tuesday. This brings the total number of Saturnian satellites to 274.

Irregular moons. The 128 newly discovered satellites are categorized as irregular moons. These potato-shaped moons are just a few miles in diameter and exhibit retrograde orbits, meaning they revolve around Saturn in the opposite direction of its rotation.

Unlike regular moons, such as Titan and Enceladus, irregular moons orbit at much greater distances and follow highly inclined or elliptical trajectories. Most of these moons were likely gravitationally “captured” by Saturn rather than having formed within the original protoplanetary disk.

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The challenge of naming the new moons. Tentative letter and number designations, such as S/2020 S1 and S/2019 S14, currently identify the 128 new moons. Like all of Saturn’s moons, the IAU will eventually give them names derived from Gallic, Norse, or Inuit mythology.

The moons will generally be classified based on their orbital characteristics and potential common origins. The Norse group has several subgroups. For instance, Phoebe includes moons that are close to the moon Phoebe, suggesting they may have originated from collisions that fragmented it. Mundilfari consists of moons associated with recent collisions, while Kari comprises satellites related to multiple captures or fractures.

How many more moons are yet to be discovered? Despite advancements in telescopes and image analysis techniques, astronomers seem to have reached the limit of what they can systematically detect around Saturn with current technology.

There’s some evidence that even smaller objects may exist. However, limitations in instrumentation, light scattered by the planet, the Earth’s atmosphere, and the sensitivity of the telescopes make it challenging to detect anything further.

Image | NASA

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