- Twenty new moons of Saturn were announced yesterday, bringing the sixth planet’s moon count to 82.
- The ringed planet’s new moon count surpasses that of Jupiter (which currently has 79 moons), the current record holder for most orbiting bodies in the solar system.
- It’s likely that these new moons were once part of a larger parent moon, and then split off after collisions around Saturn.
Jupiter has long held the record for the number of satellites orbiting a planet in the solar system, but that title has now gone to another planet: Saturn. Twenty new moons of Saturn have been discovered, pushing the ringed planet’s moon count to 82—three more than Jupiter, which has 79 orbiting moons—according to an announcement made on Monday by the International Astronomical Union.
“Studying the orbits of these moons can reveal their origins, as well as information about the conditions surrounding Saturn at the time of its formation,” team leader Scott Sheppard said in a statement. Saturn’s moons have a violent past. Many of the relatively tiny moons, each of which are no more than 3 miles across, were likely part of larger bodies and then splintered apart as they collided with one another.
Three of the moons orbit Saturn in prograde, which means they orbit the planet in the same direction as it rotates. Seventeen of the moons orbit Saturn in retrograde, meaning they circle the planet in the opposite direction of its rotation. Two of the 20 newly discovered moons (both prograde) orbit close to Saturn, taking roughly two years to circle the planet. The more distant of the newly discovered moons (including all the retrograde and one prograde moon) take more than three years to complete the journey.
The new moons have been sorted into three existing groups—all based on mythologies from Earth and sorted by the curious inclination angles of their orbits. Two of the three prograde moons fit within the Inuit group, which have angles of inclination of around 46 degrees. They were likely once part of a parent moon. So, too, were members of the Norse moon group, which includes all of the newly discovered retrograde moons. The Norse moons have an angle of inclination similar to those of the Inuit group.
The third newly discovered prograde moon belongs to the Gallic group, which have an average angle of inclination of around 36 degrees and has the farthest stretching orbit of any of the prograde moons.
“The fact that these newly discovered moons were able to continue orbiting Saturn after their parent moons broke apart indicates that these collisions occurred after the planet-formation process was mostly complete and the disks were no longer a factor,” said Sheppard. Along with the University of Hawaii’s Jan Kleyna and UCLA’s David Jewitt, the co-discoverer of the Kuiper Belt, Sheppard spotted the moons while using the Subaru telescope atop Hawaii’s Mauna Kea volcano.
Now that these new moons have been discovered, it’s time to name them—and Sheppard and his colleagues want your help. They launched a contest to name the moons on Oct. 7 and will accept nominations until December 6, 2019. Check out the rules here.
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