Aww, I feel sorry for Jupiter. The solar system’s largest planet also had the most moon critters circling around it — 79 total. No more. With the help of the giant Subaru telescope atop Mauna Kea in Hawaii 20 new moons were recently added to Saturn’s tally making 82 and crowning it the new king of the moons!
Most of the new objects are only about 3 miles (5 km) in diameter. 17 of them orbit the planet backwards, or retrograde, opposite the direction Saturn rotates. The other three orbit in the normal direction, or prograde. Two of the prograde moons are closer to the planet and take about two years to travel once around Saturn. The more distant retrograde moons and one of the normal moons each take more than three years to complete an orbit.
To get a feel for how far away these moons are from Saturn consider that Titan, the brightest and easiest to see in a telescope, takes just 16 days to complete an orbit at a distance three times that of Earth’s moon. Many of the new ones orbit around 12.5 million miles (20 million km) from the planet.
Scott Sheppard, a faculty member at the Carnegie Institution for Science in Washington, D.C., led the team of astronomers who discovered the moons. Sometimes you just can’t beat the power of the human eye-brain connection. To find them Sheppard combed through old images taken by the Subaru scope a decade ago and looked for any faint blips the automated program might have missed. He estimates that least 100 moons with a diameter of at least a mile orbit the planet. But to spy any more of these tiny niblets will take bigger telescopes. In truth, Sheppard’s the real moon king — last year alone, he discovered 12 new moons orbiting Jupiter.
The inner moons of Saturn all orbit in the same direction as Saturn rotates, but the outer moons appear to be grouped into three different clusters based on the inclinations of their orbits. Two of the newly discovered prograde moons fit into a group of outer moons with inclinations of about 46° called the Inuit group, named for characters in Inuit mythology. The retrograde moons are all members of the Norse group (Norse mythology) because they have inclinations like the previously known retrograde Saturnian moons. The other newly found prograde moon has an inclination near 36°, which is similar to the other known grouping of inner prograde moons around Saturn called the Gallic group (Celtic mythology). Each of the three groups are fragments of once-larger moons that were shattered when struck by passing comets or asteroids.
“In the solar system’s youth, the sun was surrounded by a rotating disk of gas and dust from which the planets were born. It is believed that a similar gas-and-dust disk surrounded Saturn during its formation,” Sheppard said.
Earlier this year, Carnegie held a contest to name some of Jupiter’s newly discovered moons. They’re doing the same this time around with the new discoveries at Saturn. For the two moons belonging to the Inuit group, the names must come from Inuit mythology. The 17 retrograde moons must be named after characters from Norse mythology, and the single Gallic moon must be named after a Celtic mythological giant. The deadline for submissions is Dec. 6, 2019.
Tweet your suggested moon name to @SaturnLunacy and tell Carnegie why you picked it. Photos, artwork, and videos are strongly encouraged. Don’t forget to include the hashtag #NameSaturnsMoons. You’ll find more contest details here.