For centuries, Saturn‘s bevy of moons has captivated astronomers who dedicate their lives to studying the breathtaking diversity of our solar system. As the second largest planet after Jupiter, ringed Saturn and its 62 confirmed moons offer insight into the formation and evolution of our cosmic neighborhood.
The exciting tally of how many moons Saturn has is constantly growing as new technology reveals smaller moons than ever before observed. Today‘s count stands at an astonishing 82 confirmed moons and counting – surpassing even Jupiter as the planet with the most known moons!
Let‘s voyage through the history of saturnian moon discoveries, meet the major moons that account for over 99% of orbiting mass, get to know the menagerie of minor moon groups, and ponder why the count continues to change over time.
The Historic Discovery of Saturn‘s Moons
Humans have marveled at Saturn‘s moons for centuries since the first telescopic observations in the early 1600s. Christiaan Huygens, who built his own telescope lenses, recorded the first sighting of a Saturnian moon – Titan – in 1655. Huygens was stunned by Titan‘s massive size compared to other moons known at the time.
Giovanni Cassini discovered moons Tethys, Dione, Rhea and Iapetus in 1671-84. Cassini accurately described the changing appearance of Saturn‘s rings and hypothesized their composition as "myriads of tiny moons."
William Herschel spotted Mimas and Enceladus in 1789. Herschel famously discovered Uranus and expanded astronomy‘s reach with telescopes he built himself. His son John Herschel called Enceladus "an object of supreme interest and beauty."
After a long gap with no new moons, William Lassell identified Hyperion in 1848. Lassell was famed for also discovering Neptune‘s large moon Triton.[(Table of first 10 discovered moons and their discovery years)]
The advent of long-exposure photographic plates fundamentally changed observers‘ power to uncover new moons. At the start of the 20th century, Saturn‘s confirmed moon count was a mere 10. Improved observation technology like spacecraft visits and digital imaging has since dramatically multiplied the number of known moons.
Introducing Saturn‘s 7 Major Moons
While Saturn has over 80 orbiting moons, just 7 account for 99.966% of the mass surrounding the planet. These major moons are each exceptionally unique worlds:
(Details on composition, special traits, and size comparisons)
- Titan – The giant orange moon swathed in a thick nitrogen atmosphere with methane lakes. At 5,150 km wide, Titan is Saturn‘s largest moon and the solar system‘s second largest, surpassed only by Jupiter‘s Ganymede.
- Rhea – Icy Rhea has been called the "dirty snowball" moon. With a diameter of 1,528 km, it is the solar system‘s 8th largest moon. Rhea is believed to have a water ocean beneath the frozen surface.
- Iapetus – Saturn‘s 3rd largest moon at 1,470 km across has a striking two-tone coloration making it resemble a giant walnut. Iapetus has one bright, heavily cratered hemisphere and one extremely dark hemisphere.
- Dione – A dense rocky core lies beneath an icy shell enclosing craters and canyon-like cliffs towering hundreds of meters high. At 1,123 km wide, Dione is about a third the width of Earth‘s moon.
- Tethys – Cold and crater-riddled Tethys measures 1,062 km across, similar to the sizes of Saturn‘s moons Enceladus and Mimas. Tethys is home to Odysseus crater which spans a staggering 400 km, enveloping nearly the moon‘s whole surface.
- Enceladus – Remarkably, little 500 km wide Enceladus shows signs of active geology, erupting water vapor plumes through warm cracks in the ice that may indicate a sub-surface ocean. Its ridges, fractures and smooth plains are among the youngest surfaces in the solar system.
- Mimas – The smallest major moon at just 396 km in diameter, icy Mimas is often compared to the "Death Star" due to the giant Herschel crater 130 km wide giving it a distinctive appearance.
These seven major moons constitute over 99.9% of the mass orbiting Saturn. But the smaller, minor moons reveal their own unique stories about Saturn‘s cosmic realm.
The Beautiful Diversity of Saturn‘s Minor Moon Groups
Beyond the major moons, Saturn hosts over 75 confirmed smaller natural satellites categorized into these main orbital groups:
- The Alkyonides – Methone, Anthe, and Pallene comprise a small family of moons named for the Alkyonides of Greek myth. These tiny irregularly shaped moons no more than a few km wide orbit between Mimas and Enceladus.
- Ring Shepherds – Help corral and shape the edges of Saturn‘s rings. Notable examples are Prometheus and Pandora, the "shepherding moons" discovered by the Voyager spacecraft.
- Ring Moonlets – Likely numbering in the hundreds, these moons just 1 km or less in size inhabit Saturn‘s rings themselves and represent debris from larger moons that shattered. Their gravity helps sculpt ring structures.
- Co-orbitals Janus and Epimetheus – Remarkably, these two moons share the same average orbital distance from Saturn and periodically swap positions. Janus is larger at 180 km width while Epimetheus is 116 km wide.
- Trojan Moons – Trojans orbit 60° ahead or behind another moon. Tethys has two Trojans, Telesto and Calypso, that lead and trail it along its orbit.
Outer Irregular Moons
- Phoebe – The largest outer moon at 220 km wide, Phoebe orbits opposite the direction of Saturn‘s rotation and may have originated in the Kuiper Belt. Its backwards orbit points to Phoebe as a captured asteroid.
- Norse Group – A loose association of outer moons named after Norse mythology that orbit inclinations around 40°. They may be fragments of a larger destroyed moon.
- Inuit Group – Another grouping of outer irregulars named after Inuit mythology with inclinations near 75°.
- Gallic Group – The last grouping named after French folklore characters orbits at inclinations of around 55°.
- Additional families – More unnamed groupings share similar orbits indicating a possible common origin based on asteroid collision fragmentation.
Saturn‘s menagerie of minor moons contribute their own insights into the planet‘s origins and cosmic interactions. Discoveries of new irregular moons likely captured by Saturn‘s gravity often increase the official moon count.
Why Does Saturn‘s Moon Count Keep Changing?
The tally of Saturnian moons has grown enormously thanks to advances in telescopic photography and digital imaging combining with flyby spacecraft data. Our ability to see smaller objects far from Saturn continues expanding the confirmed moon total.
When Voyager 1 reached Saturn in 1980, it tallied 10 moons (the first 10 discovered historically). By 1990 we knew of 18 moons. The Cassini orbiter mission identified an additional 8 moons during its 13 years circling Saturn up through 2017. Meanwhile, computerized telescopes add to the count as they spy hard-to-see outer moons less than 1 km wide.
As of November 2022, Saturn‘s moon count stands at 82 confirmed plus another 20 provisional moons awaiting official designation. Tiny crumbs of moons can now be detected beyond Saturn‘s brighter rings and closer moons. Irregular moons perturbed by Saturn‘s gravity during the solar system‘s early history get periodically captured into short-term elliptical orbits, adding to the tally.
There are likely hundreds more not yet big or close enough to identify. But as technology inevitably improves, Saturn‘s bursting moon count will continue to expand just as astronomers centuries ago could not have imagined over 80 moons in orbit.
The multitude of unique Saturnian moons waiting to be studied will shape our understanding of how planets and their natural satellites evolve. Each new moon adds one more clue to deciphering the origins of Saturn‘s cosmic realm.