Saturn's biggest ring is weird, invisible and really, really big

The Phoebe ring takes up as much space as about 7,000 Saturns, most of it pieces of dust smaller than the width of a human hair.

Eric Mack Contributing Editor
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Eric Mack
2 min read

The Phoebe Ring dwarfs Saturn and its other rings. NASA/JPL/Space Science Institute

Back in 2009, NASA's Spitzer Space Telescope detected that Saturn had a massive and practically invisible outermost ring millions of miles wide, but there wasn't enough data at the time to describe it more precisely. New data and analyses show the so-called Phoebe ring is even larger and weirder than originally suspected.

The outermost ring begins about 3.75 million miles from Saturn and is itself more than 6 million miles wide. In other words, you could line up about 170 Saturns across the width of the ring -- the entirety of the thing is estimated to span an area of space about 7,000 times larger than the planet that holds it captive.

And yet, the ring itself is made up mostly of practically invisible dark dust particles smaller than the width of a human hair. This gives the Phoebe ring -- named for the moon of Saturn within it that is also the main source of the ring's material -- its invisible quality; scientists only know of its existence thanks to infrared observations done with Spitzer and NASA's WISE spacecraft.

For comparison, the more familiar inner rings of Saturn are typically made up of large chunks of ice and rock somewhere between the size of a soccer ball and a house.

Based on new WISE data, these findings -- from a team led by Douglas Hamilton, a professor of astronomy at the University of Maryland in College Park -- were published Wednesday in the journal Nature.

Word of the newly updated massive size of Saturn's total ring system will surely come as a bummer to fans of the up-and-coming ring system around distant exoplanet J1407b, originally believed to be some 200 times wider than Saturn's.

Scientists hope to take a closer look at the massive ring that's made up of a whole lot of nearly nothing using some of our large ground telescopes here on Earth, like those on Hawaii's Mauna Kea.

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