New moons rising: Saturn runs rings around Jupiter
The solar system has a new winner in the moon department.
Twenty new moons have been found around Saturn, giving the ringed planet a total of 82, scientists said this week. That beats Jupiter and its 79 moons.
“It was fun to find that Saturn is the true moon king,” astronomer Scott Sheppard, of the Carnegie Institution for Science, said.
If it’s any consolation to the Jupiter crowd, our solar system’s biggest planet — Jupiter — still has the biggest moon. Jupiter’s Ganymede is almost half the size of Earth. By contrast, Saturn’s 20 new moons are minuscule, each barely 5km in diameter.
Sheppard and his team used a telescope in Hawaii to spot Saturn’s 20 new moons this year. About 100 even tinier moons might be orbiting Saturn, still waiting to be found, he said.
Astronomers have pretty much completed the inventory of moons as small as 5km around Saturn and 1.6km around Jupiter, according to Sheppard. Larger telescopes will be needed to see anything smaller.
It was harder to spot mini moons around Saturn than Jupiter, Sheppard said, given how much farther away Saturn is.
“So seeing that Saturn has more moons, even though it is harder to find them, shows just how many moons Saturn has collected over time. These baby moons may have come from larger parent moons that broke apart right after Saturn 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 Saturn rotates. They’re so far from Saturn that it takes two to three years to complete a single orbit.
“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 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.
This week’s announcement came from the International Astronomical Union’s Minor Planet Centre.