In moons, Saturn beats Jupiter

20 more satel­lites found in or­bit

Baltimore Sun - - NATION & WORLD - By Mar­cia Dunn

CAPE CANAVERAL, Fla. — 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,” said as­tronomer Scott Shep­pard of the Carnegie In­sti­tu­tion for Sci­ence.

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 3 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 Saturn, still wait­ing to be found, he said.

As­tronomers have pretty much com­pleted the in­ven­tory of moons as small as 3 miles around Saturn and 1 mile around Jupiter, ac­cord­ing to Shep­pard. Fu­ture larger tele­scopes will be needed to see any­thing smaller.

It’s harder spot­ting mini moons around Saturn than Jupiter, Shep­pard said, given how much far­ther 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,” he wrote in an email. 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 wrote.

Just 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. For now, Saturn has the most known moons.

The an­nounce­ment about Saturn’s moons came from the In­ter­na­tional Astro­nom­i­cal Union’s Mi­nor Planet Cen­ter.

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