b'16 Carnegie Science|Spring 20 |Spring/Summer 2020 20Moons, Moons, and More Moons for Jupiter and Saturn!Public Helps with NamesO bservations led by Carnegies Scott Sheppard resulted in the July 2018 announcement of the discovery of 12 new moons orbiting Jupiter. More recent research by Sheppard and team, released in October 2019, revealed 20 new moons orbiting Saturn, bringing that worlds total number of moons to 82, surpassing Jupiters 79. Jupiters New MoonsThese discovery images show a moon orbiting Saturn in Until October, Jupiter ruled with the mostEach of the newly discoveredOctober 2019. The images, taken about one hour apart, moons of any planet in the Solar System.Saturnian moons is about 3 miles (5show the movement of the moon against a background Of the new moons, 11 are normal outerkilometers) in diameter. Seventeen of themfield of stationary stars (orange bars).moons while one is an oddball. Theorbit in retrograde direction. The otherImage courtesy Scott Sheppard, Carnegie Institution for Science oddball, named Valetudo, is more distantthree moons orbit in the prograde. are inclined to the planet. Two of the newly and more inclined than the group of moonsTwo of the prograde Saturnian moonsdiscovered prograde moons fit into a group that orbit in the same direction of Jupitersare closer to the planet and take about twoof outer moons with inclinations of about spin (prograde), and it takes about a yearyears to orbit. The more-distant retrograde46 degrees called the Inuit group, named and a half to orbit. The oddball also has anmoons and one of the prograde moonsafter Inuit mythology. orbit like no other known Jovian moon: iteach take more than three years toThe Inuit moons may have once been crosses the outer retrograde moons, whichcomplete an orbit. part of a larger moon that broke apart. orbit in the opposite direction. Its alsoStudying the orbits of these moonsLikewise, the newly announced retrograde Jupiters smallest known moon, at lesscan reveal their origins, as well asmoons have inclinations indicating that than 0.6 miles (1 kilometer) in diameter.information about the conditionsthey are also likely fragments from a surrounding Saturn at the time of itsonce-larger parent moon that broke apart. Saturns New Moons formation, Sheppard explained.These retrograde moons are in the Norse Jupiter fell from its lunar laurels with theThe outer moons of Saturn appear togroup, with names coming from Norse more-recent discovery of Saturns newbe grouped into three different clustersmythology. One of the newly discovered moons. categorized by the angles that their orbitsretrograde moons is the farthest known moon around Saturn.In the Solar Systems 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. 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. The new moons were discovered using the Subaru telescope on Mauna Kea in Hawaii. The observing team included Sheppard, David Jewitt of UCLA, and Jan Kleyna of the University of Hawaii.Using some of the largest telescopes in the world, we are now completing the inventory of small moons around the giant Carnegies Scott Sheppard (left) is with colleagues Dave Tholen (middle) of the University of Hawaii Institute forplanets, Sheppard remarked. They play a Astronomy and Chad Trujillo (right) with Northern Arizona University in the Subaru telescope control room oncrucial role in helping us determine how our Mauna Kea in Hawaii.Image courtesy Carnegie Institution for ScienceSolar Systems planets formed and evolved.'