Saturn and its moons. And its moons. And its moons. And its moons.

In early March, Saturn’s satellite count stomped up of nan remainder of nan Solar System pinch announcements bringing nan ringed planet’s full satellite count to 274 earthy satellites. This is almost doubly arsenic galore arsenic each nan moons astir each nan different planets added together, totalling ‘only’ 142 moons, of which 95 orbit Jupiter. 

Saturn is already good known for its absorbing moons. Its largest satellite Titan, astir 50% larger than Australia, is nan only satellite successful nan star strategy pinch an atmosphere, and nan only other object in nan star strategy speech from Earth pinch lakes and rivers connected its surface. Unlike Earth however, these lakes are made of liquid methane – virtually rocket fuel, while nan ambiance is made mostly of nitrogen. 

Image: Titan, pinch lakes visible done nan hazy ambiance successful nan apical left. Credit: NASA / JPL-Caltech / Space Science Institute 

Titan is (arguably) edged retired of nan ‘most absorbing Saturnian moon’ spot by Enceladus. This icy moon, astir arsenic wide broadside to broadside arsenic nan region from Perth to Kalgoorlie, is known to have subsurface oceans of liquid h2o beneath its tortured stiff exterior. The aboveground of Enceladus bears ample cracks, somewhat for illustration nan fragmenting of Earth’s aboveground into tectonic plates. At anemic points successful nan surface, molten crystal (aka water) tin unit done and erupt arsenic crystal volcanos.  

Image: Ice volcanos connected Enceladus, pinch nan cracked icy aboveground visible. Credit NASA/JPL-Caltech/SSI/CICLOPS/Kevin M. Gill. CC BY 2.0 

Titan and Enceladus are portion of a group of 24 Saturnian moons classified as regular moons. Most of these moons orbit almost straight supra Saturn’s equator and move prograde, successful nan aforesaid guidance that nan satellite rotates. Astronomers mostly deliberation nan regular moons formed pinch Saturn billions of years agone arsenic nan satellite coalesced from nan primordial disk that formed our star system.  

Regular moons are truthful named to separate them from remaining 250 moons, classified as irregular moons. The orbits aliases these irregular moons are overmuch much scattered, often greatly tilted to Saturn’s equator, galore of them orbiting retrograde – in nan different guidance to Saturn’s rotation – and conscionable mostly being messy. All 128 of nan recently announced moons are irregular moons. 

Image: Irregular satellite orbits of Saturn. Prograde orbits coloured bluish and retrograde orbits coloured red. 
Credit: Nrco0e – Own work, CC BY-SA 4.0,

It is worthy pointing retired that nan recently announced moons were really discovered a while ago. They were picked retired of observations mostly performed betwixt 2019 – 2023, but immoderate information goes arsenic acold backmost arsenic 2004. The logic they are successful nan news now is they person been officially recognised by the International Astronomical Union, nan governing world assemblage connected astronomical matters.  

These caller moons are tiny, only a fewer km across, making them extraordinarily difficult to spot. Astronomers usage a method called ‘shift and stack’, fundamentally a fancy measurement of saying adding nan information together (stack) while accounting for nan mobility of Saturn (shift). In immoderate 1 image you won’t spot much, but adding tons of observations together allows a anemic awesome to guidelines retired from ambient noise.  

Image: The displacement and stack method allows faint objects to beryllium seen successful different difficult to construe data. Bright streaks are inheritance stars. Credit: Edward Ashton/CFHT/Canadian Astronomy Data Centre, processed by Nrco0e – Own work, CC BY-SA 4.0,  

Finding caller moons of Saturn isn’t conscionable a mindless intelligence exercise. The constituent is to look for patterns and interestingly, astir of Saturn’s irregular moons have uncorrelated orbits, giving america clues to its history. If nan irregular moons were formed by, for example, a azygous ample satellite breaking into pieces, past we would still expect them to have similar orbits. While location are immoderate similarities betwixt smaller subgroups of irregular moons, nan deficiency of wide relationship suggests that nan irregular moons of Saturn travel from perchance galore smaller moons progressive successful breaking isolated aliases violently colliding, aliases both, successful either order. There is besides nan anticipation immoderate of them are captured asteroids. Teasing retired nan history of nan star strategy from a fewer faint pixels successful a photograph is immoderate powerful science. 

This astir apt won’t beryllium nan past we’ll perceive astir moons astir nan outer planets but moreover based connected what we person discovered truthful far, an absorbing shape emerges. When you crippled really galore moons of a fixed size Saturn has compared to Jupiter, Saturn still leads by much than 3 times for nan information available, suggesting that Saturn intrinsically has much moons than Jupiter, different absorbing hint that mightiness beryllium hinting astatine thing deeper. 

Image: Number of moons of Jupiter and Saturn classed by size shows Saturn intrinsically has much moons. Credit: Ashton et al. 2021 

This each does request nan mobility of what is simply a moon? And really mini is excessively small? At nan infinitesimal location is nary statement among astronomers wherever to tie nan statement for what is simply a moon. Most group would work together that nan trillions of particles of crystal that dress up Saturn’s rings astir apt don’t fresh nan measure of being called a moon. Somewhere successful location is an answer, but much subject is needed to really understand what makes moons guidelines retired from nan rubble.  

Image: The mini satellite Pan orbits wrong Saturn’s rings and has an equatorial disk made from accreted ringing material. Credit: NASA/JPL-Caltech/Space Science Institute