Saturn is the solar system's 'moon king', with 20 more spotted

Saturn is now being recognised as the "moon king" of our solar system, with astronomers spotting 20 more of them orbiting the giant ringed planet, bringing its total count to 82 - three more than Jupiter.

The newly identified small moons, ranging from about 3km to 6km in diameter, were detected using the Subaru telescope in Hawaii by a research team led by astronomer Scott Sheppard of the Carnegie Institution for Science in Washington.

"Saturn is the moon king," Sheppard said in an email interview yesterday.

The discovery was announced this week by the International Astronomical Union's Minor Planet Centre.

One of the moons orbits at an astounding distance of about 24 million km from Saturn, farther away than any of its other moons. By comparison, Earth's moon orbits about 386,000 km from the planet.

Seventeen of the newly detected Saturnian moons are orbiting in the opposite direction of the planet's rotation. The other three orbit in the same direction Saturn spins, as is typically the case.

A number of the moons appear to be fragments of once-larger moons that broke up in long-ago collisions with other moons or passing comets or asteroids, Sheppard said. That is similar to some of the 79 moons orbiting Jupiter.

Saturn, a gas giant made up mostly of hydrogen and helium, is the second-largest planet in the solar system and the sixth from the Sun. Its diameter of about 116,000km dwarf's Earth diameter of about 12,700km.

Only Jupiter, the fifth planet from the Sun, is larger. Saturn formed with the other planets and the sun about 4.5 billion years ago.

"These new moons show us the solar system was a very chaotic place in the distant past, with objects flying all over the place. These are the last remnants of the objects that formed in the giant planet region, as all of the other objects that formed in this region have either been ejected or incorporated into the planets themselves," Sheppard said.

The newly identified moons are much smaller than Saturn's largest, the icy world Titan, whose diameter of about 5,150km exceeds that of the innermost planet, Mercury.

"We believe Saturn likely has about 100 moons larger than 1.6km, but the discovery of these new moons that are about 3.21km to 6.43km in size is pushing the limit of our current ability to find them. We will need the next generation of large telescopes to find smaller moons," Sheppard added.

- Reuters