Saturn's Ring System Just Got Bigger

Okay, the rings themselves haven't changed at all.  But it turns out that there is an outer dust ring that is about 24 million kilometers in diameter composed of dust grains that do not reflect visible light.  Because of that, it hasn't been seen before.  NASA has a short (very short) press release showing an artist's conception of what the ring looks like in infrared that helps you get a sense of scale.  But even that is hard.  For comparison, the distance from the Sun to the Earth is about 150 million kilometers.  So the diameter of this dust ring is 1/6 the distance from the earth to the Sun.  Light takes 8-1/2 minutes to travel from the Sun to the Earth, it takes over a minute to travel from one side of this ring to the other.  That's big.

That actual image from the Spitzer Space Telescope is less impressive simply because right now, Saturn's rings appear edge-on to us so we don't get that beautiful tilted view.  Several other images are also available.

According to researchers, this new ring is likely caused by debris which is coming off the tiny moonlet Phoebe whose orbit lies right in th middle of the ring.  Additionally, Saturn's moon Iapetus has always been something of a mystery with one side significantly brighter than the other.  Iapetus is tidally locked with Saturn, so one face is always pointed at Saturn and one side away, just like our own moon.  That also means that the same side is always pointed in the direction of its orbit and another away.  The leading side is much darker than the trailing side as if it were running into a storm of dust and getting coated by the stuff.  Now that this dust from Phoebe has been discovered, it looks like that is exactly what is happening.  Iapetus is running into the dark dust coming off Phoebe and the front-side is darkened by it.