Saturn overthrows Jupiter as planet with most moons after 20 discoveries

Scientists at the American Carnegie Science Institute have discovered twenty new moons orbiting the planet Saturn, thanks to computer algorithms. With that, Jupiter is no longer the planet in our solar system with the most moons.

Astronomer Scott Sheppard’s team discovers that Saturn now has 82 moons, while Jupiter has 79. The 20 new discoveries are all very small moons, about 5km in diameter. 17 of these moons orbit Saturn in the opposite direction to Saturn’s rotation, or retrograde, and take more than three Earth years to complete one orbit. The three remaining newly discovered moons orbit Saturn in the same direction as the ring planet’s rotation. Two of these are closer to Saturn and take two years to orbit the planet, while the third takes more than three years.

According to the discoverers, the outer moons appear to be grouped into three distinct clusters, given the inclination of their angles when orbiting Saturn. Most of the new moons are believed to have come from larger moons broken up in the past. “This kind of grouping of outer moons is also visible at Jupiter, suggesting violent collisions between moons in the Saturn system or with outside objects, such as asteroids or comets,” Sheppard said.

Two images of the Subaru telescope with an hour between them. The stars in the background didn’t move, but this newly discovered moon, marked with two dashes, did move.

The newly discovered moons are believed to have formed only after Saturn was fully formed, when the planet’s past disk of gas and dust was no longer a factor. If the suspected larger moon disintegrated during the phase when the large amount of gas and dust was still present, there would have been strong friction between the gas and the smaller moons, causing them to crash on Saturn. According to Sheppard, studying the discovered moons can reveal more about their origins, as well as information about the conditions around Saturn during its formation.

The new moons were found with the Subaru telescope at the Mauna Kea Observatory in Hawaii. This telescope from the National Astronomical Observatory of Japan has a mirror with a diameter of 8.2m. Subaru is the Japanese name for Pleiades, an open star cluster visible to the naked eye from Earth in the constellation Taurus, located 440 light years from Earth.

The discoveries were made possible by applying new algorithms to data collected with the telescope between 2004 and 2007. These algorithms were able to match orbits to potential moons identified in the ancient data. “We thought they were Saturn’s moons, but we couldn’t determine full orbits before to be sure,” Sheppard told the BBC. According to him, more moons around Saturn can be discovered in the future that are even smaller, with diameters of about a kilometer. However, this requires larger telescopes first.

Sheppard also discovered twelve new moons around Jupiter last year and launched a competition to come up with names for the objects. The same is now also on the agenda; interested parties have until December 6 to submit names. There are a number of rules attached to this. The moons belong to different groups named after different mythologies, so creators should come up with names of giants from Norse, Gallic, or Inuit mythology.