My Dark Sky

Saturn’s rings are gorgeous – I think no one will disagree with me… these rings are easily visible through small telescope. But what you can see are just the “small” rings. Recently the Spitzer Space Telescope has spied an enormous ring around Saturn, by far the largest of its many rings.

This artist’s conception shows a nearly invisible ring around Saturn — the largest of the giant planet’s many rings. It was discovered by NASA’s Spitzer Space Telescope.
Credit: NASA/JPL-Caltech/Keck.

This new ring is about 6 million km away from Saturn and extends outward roughly another 12 million km. Phoebe, one of Saturn’s farthest moons, circles within this ring, and is likely to be the source of its material.

The ring is tenuous, made up of a sparse collection of ice and dust particles. If you could transport yourself to the ring, you wouldn’t even know you were there because the particles are so far apart. It’s difficult to see in visible light – the relatively small numbers of particles in the ring wouldn’t reflect much visible light, especially out at Saturn where sunlight is weak. That’s why it takes so long to find something this big. However, if we look in infrared, then it’s a different story. With Spitzer’s infrared eyes we were able to spot the glow of the ring’s cool dust.

This diagram illustrates the extent of the largest ring around Saturn. The moon Phoebe circles within this ring. The pictures of Saturn, Phoebe and Iapetus were taken by NASA’s Cassini spacecraft. The ring is an artist’s illustration.
Credit: NASA/JPL-Caltech.

The discovery of this ring was no accident: astronomers were purposely searching for it hoping to solve an age-old riddle of Saturn’s third largest moon Iapetus. Iapetus has a strange look. It has one bright side and the other really dark side – a yin-yang moon, why?

Astronomers have long suspected that there is a connection between Phoebe and the dark material on Iapetus. They had a hunch that Phoebe might be circling around in a belt of dust kicked up from its minor collisions with comets. Sure enough, when they took a first look at their Spitzer data, a band of dust jumped out.

The discovery of this new ring provides convincing evidence of the relationship. The ring is circling in the same direction as Phoebe, while Iapetus is going the opposite way. According to the scientists, some of the dark and dusty material from the outer ring moves inward toward Iapetus, and slam the icy moon like bugs on a windshield.

So there you go, another mystery solved…

Posted in Saturn