Astronomers have found 20 new moons circling Saturn — now you can help name them!
Jupiter may be the king of the planets, but — right now, at least — Saturn is the king of moons. Astronomers Scott Sheppard (Carnegie Institution for Science), David Jewitt (UCLA), and Jan Kleyna (University of Hawai‘i) have announced the discovery of 20 new moons circling the ringed planet, putting Saturn’s total at 82 compared to Jupiter’s 79. The moons are each around 5 kilometers (3 miles) in diameter.
The team used the Subaru telescope atop Maunakea, Hawai‘i, to find the moons. Sheppard had previously led a team in discovering of 10 new moons around Jupiter, announced last year, using the 6.5-m Magellan-Baade reflector Las Campanas and the 4.0-m Blanco reflector on Cerro Tololo.
"Using some of the largest telescopes in the world, we are now completing the inventory of small moons around the giant planets,” Sheppard explains. The new discoveries are cool in and of themselves, but ultimately, it’s what they tell us about the solar system’s formation that motivates Sheppard’s search.
Of the 20 new moons, 17 are orbiting the moon “backwards,” that is, in a direction opposite to the planet’s motion. Astronomers call these orbits retrograde. They’re all at roughly the same distance from the planet, putting them in the Norse group of moons. The Norse group is diverse, but the orbits and inclinations of the newest moons suggest they all originated from the same parent body.
Three other moons are in prograde orbits, two orbiting at an inclination of 46° and one at an inclination of 36°. They belong to the Inuit and Gallic groups, respectively.
See Sheppard’s visual summary of Saturn’s moons here, and peruse Sky & Telescope's catalog of solar system moons old and new here.
Watch a humorous take on the discoveries and what they mean for the moons’ formation here:
Name Those Moons!
You have until December 6, 2019, to tweet your suggested moon name to @SaturnLunacy with the hashtag #NameSaturnsMoons. Describe why you picked the name you did, and include photos, artwork, and videos to bolster your case.
It’s not the Wild West out there — the International Astronomical Union has rules for naming things in outer space, and the moons of Saturn are no exception. Saturn’s moons are named for mythological giants, and which mythology depends on which group the moon belongs to.
Two of the newly discovered prograde moons must be named for giants from Inuit mythology. One moon, which is also prograde but belongs to a different group, is to be named for a giant in Gallic mythology. Likewise, 17 retrograde moons must be named for giants in Norse mythology. Be sure to search the current database of IAU names to make sure the name you’ve picked out isn’t already in use.