What the heck is a moonlet?

Allison Loudermilk

NASA/JPL/Space Science Institute

Why it's a diminutive moon -- a small natural or artificial satellite -- of course. Thanks to NASA's Cassini spacecraft, we know now there's one circling Saturn in its G ring. In the picture, it's that microscopic bright spot that NASA helpfully points out within the square.

It truly is tiny, clocking in at about a third of mile across. Compare that to the hefty girth of the Earth's moon, which has a diameter of 2,160 miles (3,475 kilometers), and you can see why it gets the cute name. And the G ring, for those of us who tend to forget these things, is the second outermost ring in Saturn's impressive collection -- D, C, B, A, F, G and E.

Like the rest of the universe's pint-sized participants, the new moonlet may be on the receiving end of some bullying. The larger, nearby moon Mimas is disturbing the moonlet's orbit and generally letting it know who's boss, according to the NASA press release.

But the really big deal about Cassini's finding is that it solved a mystery, as Phil Plait points out in his always excellent blog. The G ring is generally a dusty place, but until now , they couldn't say with certainty what was causing all the dust. Turns out it was the moonlet.

Check. Another universal mystery solved. Next, please. While you're pondering that, we have plenty more reading for you to moon over at HowStuffWorks.com: How Lunar Rovers Work How Lunar Landings Work What are Saturn's rings made of? Top 10 Space Conspiracy Theories