The discovery of 20 previously unknown moons Saturn helped the planet surpass all others in our solar system, according to the Planet Minor Center of the International Astronomical Union. It now has 82 known moons; Jupiter is 79.
The moons are all of similar size, measuring about five kilometers in diameter. But 17 of the 20 have a retrograde orbit of Saturn, which means they essentially orbit backwards from the planet and other moons.
Carnegie Science Institute astronomer Scott Sheppard and his team used the Subaru telescope in Hawaii to find the moons. Last year, Sheppard and his team located 12 new moons around Jupiter, including one with a retrograde orbit.
"Using some of the largest telescopes in the world, we are now completing the inventory of small moons around the giant planets," Sheppard said. "They play a crucial role in helping us determine how the planets in our solar system formed and evolved."
Two of the moons with a pro-grid orbit, or one moving in the same direction as the planet, complete a single orbit of Saturn every two years. They are closer to the planet than some of the other newly discovered moons. Other progressive and distant retrograde moons complete a single orbit every three years.
"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," Sheppard said.
These outer moons fall into three categories based on the angle of their orbit. The outermost group, which includes two of the pro-class moons, has a 46-degree angled orbit and is named after Inuit mythology. Researchers believe all of these moons may have been part of a larger moon that broke apart.
Retrograde moons were also probably part of a larger body, and its name is derived from Norse mythology.
Gas, dust and collisions in outer space
One of the prograde moons has an angle of 36 degrees, similar to the other prograde moons near Saturn, named by Gallic mythology. But the newfound moon is farther away than the others. It may be part of the moon's inner family or its orbit has been affected, pushing it further out.
"This type of grouping of outer moons is also seen around Jupiter, indicating violent collisions between moons in the Saturnian system or with external objects such as asteroids or comets," Sheppard said.
Studying the orbits of these moons helps researchers reconstruct Saturn's past. For example, if a large moon dissolved to create smaller clusters and interacted with gas and dust, they might have been attracted to Saturn.
"In the youth of the Solar System, the Sun was surrounded by a rotating disk of gas and dust from which the planets were born. A similar disk of gas and dust is believed to have surrounded Saturn during its formation," Sheppard said. "The fact that these newly discovered moons were able to continue orbiting Saturn after their mother moons split indicates that these collisions occurred after the planet's formation process was almost complete and the discs were no longer a factor."
Want to name one of Saturn's moons?
Scientists have been able to locate the new moons thanks to more robust computing power and better algorithms for tracking distant and weak objects, Sheppard said.
What's more, you – yes, you – can help name the new moons. The contest open monday and will be closed on December 6th.
"I was so excited about the amount of public engagement during the Jupiter moon naming contest that we decided to make another one to name these newly discovered Saturnian moons," Sheppard said. "This time, the moons should be named after giants of Norse, Gaul or Inuit mythology."