Jupiter may be the king of the solar system, but Saturn has a larger entourage: Today, astronomers have announced that they have discovered 20 more moons around Saturn, which is a total of 82 – the highest number for each planet in the solar system. The massive transport is just over a year after the astronomers announced 12 new moons orbiting Jupiter. With the latest discoveries, Saturn's entourage now surpasses Jupiter's 79 known natural satellites. (Research our interactive moon atlas.)
Taken together, these relatively small moons could help astronomers better understand the many collisions in the early solar system, and they could provide mature new flyby targets for future missions to the gas giants.
"One of the most exciting things about these outer moons is that there are always missions," says Scott Sheppard, an astronomer from the Carnegie Institution for Science, who discovered the planet's newest moons. Even now, three missions are in the works for Jupiter and Saturn: NASA's Europa Clipper; NASA's Dragonfly mission; and the JUICE mission of the European Space Agency.
"There are so many of these moons that there is almost guaranteed to be one of those moons located somewhere near where the spacecraft enters the Jupiter or Saturn environment," says Sheppard.
Saturn's newly discovered moons are all about three miles wide. They are so weak that they are almost at the detection limit for the Subaru telescope, a facility on Hawaiis Mauna Kea volcano with which they were discovered.
For this reason, this discovery has been going on for more than a decade. From 2004 to 2007, Sheppard and his colleagues used Subaru to explore the area around Saturn in search of undiscovered moons. As they saw some fascinating points of light, they tried to prove that these pinpricks actually orbit Saturn.
"I always had that in mind," says Sheppard. Thanks to new computer techniques, it is now much easier to analyze telescope images worth several years and find links between them. When Sheppard retraced the data, the images confirmed that 20 points of light traced orbits around Saturn.
Seventeen New Moon orbit in the opposite direction of Saturn's rotation Each of these "retrograde" moons takes more than three years to find orbit. The other three moons orbit Saturn in the same direction as the planet's rotation. Two of these "advancing" moons take about two years to complete an orbit, while the third takes more than three years to orbit around Saturn. The pictures were taken with the Subaru telescope, whereby between the individual pictures about one hour had passed. Marked with an orange bar, the newly discovered moon moves against the background of static stars and galaxies.
GIF-kindly provided by Scott S. Sheppard
These newly discovered moons intersect into previously known groups of Saturn satellites, each named after mythological groups Giant. Based on their orbital directions, distances from Saturn and their orbit inclination relative to Saturn, the retrograde moons fall into the Nordic group. The two closer moons fall into the Inuit group, while the farthest falls into the Gallic group.
Sheppard and his colleagues believe that each of these lunar clusters consists of a particular parent Saturn has trapped during the solar system's initial period. In a heavenly bumper car game, the parents' bodies dissolved in the course of time through collisions and created the now visible, fragmented moons.
"We believe these moons basically show us how chaotic the solar system was in the distant past," says Sheppard. "Basically everything was hit, and those moons are a remnant of this process."
None of the 20 new moons still has official names. Sheppard and his colleagues have called on the public to make proposals in a competition that ends on 6 December.
"A dream comes true"
Next-generation telescopes like the giant telescope Magellan built in Chile will do it Probably find even more moons surrounding the gas giants of the solar system. According to Sheppard, our best telescopes are currently unable to detect moons around Jupiter that are less than 1
"These are so far away that we only know the limit values for Uranus up to a size of 32 km or for Neptune up to a size of approximately 48 km," says Sheppard.
When more small, distant objects are found, Sheppard is more than ready for the challenge. Together with the astronomer Chad Trujillo, Sheppard previously discovered an extremely distant object with an orbit that could be pulled by an invisible "planet nine" deep on the edge of the solar system. In 2018 he found the farthest object ever seen in our solar system, a frozen spot called Farout, which is more than a hundred times as far from the sun as Earth. And only a few months later, he and his colleagues set their own record by finding an even farther object called Farfarout. When he was about 12 years old, he received a children's science magazine listing all known planets and moons, and he posted the pages on the wall of his bedroom dream, "he says.