Announced at the International Astronomical Union’s Minor Planet Centre by a team of astronomers from the Carnegie Institute for Science led by Scott S. Sheppard, the discovery is the latest advance in the 400-year history of our understanding of the satellites of our neighboring planets…..
As technology has improved, we have observed more and more of these tiny, distant worlds – and we can be reasonably confident there are still plenty waiting to be discovered.
Astronomers at the Carnegie Institution for Science, led by Scott S. Sheppard, announced the discovery of the collection of moons on October 7 at the International Astronomical Union’s Minor Planet Center. “Using some of the largest telescopes in the world, we are now completing the inventory of small moons around the giant planets,” Sheppard told his audience. He added that “They play a crucial role in helping us determine how our Solar System’s planets formed and evolved.”
Compared to Saturn’s well-known moons, including ones like Enceladus, Titan, Hyperion, and Rhea (among others), these new ones are quite tiny. For example, Titan, Saturn’s largest moon, is roughly 3,200 miles in diameter. These new tiny moon-tots? Only about three miles in diameter. But even though the newly discovered Saturnian moons are small, they still bring Saturn’s total moon count up to 82, which beats out Jupiter’s former-record number of 79. Plus, as mentioned, the moons offer new clues as to how Saturn formed in the early solar system.
“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,” Sheppard added in his announcement.
Sheppard and his team also say that the way these moons are orbiting Saturn — with seventeen of the twenty orbiting in retrograde, or in the opposite direction of the planet’s rotation — means that they were once subject to “violent collisions… between moons in the Saturnian system or with outside objects such as passing asteroids or comets.”
To confirm that these objects are indeed associated with Saturn, astronomers have to observe them over days or even months to reconstruct the shape and size of the moon’s orbit.
Many small moons are fragments of shattered large moons
Such observations revealed a population of moons that are often described as “irregular” moons. They are split into three distinct groups: Inuit, Gallic, and Norse. They all have large, elliptical orbits at an angle to those of moons closer to the planet.
Each group is thought to have formed from a collision or fragmentation of a larger moon. The Norse group consists of some of the most distant moons of Saturn, which orbit in the opposite direction to the rotation of the planet. This suggests they could have formed elsewhere and were later captured by the gravitational force of Saturn.
Of the 20 new moons, 17 belong to the Norse group including the furthest known moon from the planet. Their estimated sizes are of the order of 5 km in diameter.
Some of the newly discovered moons are very faint and at the limit of detection with currently available instruments. New, bigger telescopes such as Giant Magellan Telescope will allow us to observe even fainter objects.
In the meantime, the 20 new moons need names. Carnegie Science has invited everyone to help.