Saturn Now Has 82 Moons, More Than Any Other Known Planet

An artist’s conception of the 20 newly discovered moons orbiting Saturn. These discoveries bring the planet’s total moon count to 82, surpassing Jupiter for the most in our solar system. Courtesy of the Carnegie Institution for Science. Saturn from NASA/JPL-Caltech / Space Science Institute; starry background courtesy of Paolo Sartorio/Shutterstock

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!

Here the Subaru Telescope shoots a laser beam into the upper atmosphere to generate an artificial guide star it will use to track air turbulence. The 8.2 meter reflecting telescope was used to track down Saturn’s latest batch of moons. Daniel Birchall

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.

Saturn now has the most known moons of any planet in the solar system. Carnegie Science

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.

Saturn’s outer moons are divided into three groups or families each based on a common origin in aa long-ago break-ups of a larger moon. They named Inuit, Gallic and Norse. Click here for more details about each of the new moons. Carnegie Science

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.

Several billion years ago Saturn was surrounded by a thick disk of gas and dust similar to what formed around the early sun. Within the cloud new moons were born. Carnegie Science

“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.


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