Astronomers have discovered 20 new moons around Saturn

8 Oct 2019

Image: © Matthieu/

A team from the Carnegie Institution for Science has discovered 20 new moons orbiting Saturn, each with a diameter of around three miles.

The solar system has a new winner in the moon department: 20 new moons have been found around Saturn, giving the ringed planet a total of 82, scientists said. This beats previous record-holder Jupiter, which has 79 moons.

“It was fun to find that Saturn is the true moon king,” said astronomer Scott Sheppard of the Carnegie Institution for Science.

If it is any consolation to the Jupiter crowd, our solar system’s biggest planet still has the largest moon. Jupiter’s Ganymede is almost half the size of Earth. By contrast, these 20 newly discovered moons are minuscule, each barely three miles in diameter.

Sheppard and his team used a telescope in Hawaii to spot Saturn’s 20 new moons over the summer. About 100 even tinier moons may be orbiting the planet, still waiting to be found, he said. Future larger telescopes will be needed to see anything smaller.

It is more difficult to spot ‘mini-moons’ around Saturn than Jupiter, Sheppard said, given how much farther away it is.

“So seeing that Saturn has more moons even though it is harder to find them shows just how many moons it has collected over time,” he added.

These mini-moons may have come from larger parent moons that broke apart right after the planet formed. Seventeen of Saturn’s new moons orbit the planet in the opposite, or retrograde, direction. The other three circle in the same direction that the planet rotates.

“These moons are the remnants of the objects that helped form the planets, so by studying them, we are learning about what the planets formed from,” Sheppard said.

Last year, Sheppard and his team found 12 new moons around Jupiter. The Carnegie Institution had a moon-naming contest for them; another is planned now for Saturn’s new moons.

The jury is still out on whether any planets beyond our solar system have even more moons. For now, Saturn has the most known moons.

Monday’s announcement (7 October) came from the International Astronomical Union’s Minor Planet Centre.

– PA Media, with additional reporting by Eva Short