The Cassinin spacecraft at Saturn continues to do remarkable work. Today they announced the discovery of a small "moonlet" inside Saturn's G ring. The G ring is one of the outer rings, very thin and dusty. The G ring was also an oddball since it was the only one of the dusty rings not to be affiliated with a moon...until now. Here are the discovery images (click to embiggen).
- A new moon in Saturn's G Ring. Image Credit NASA/JPL/Space Science Institute
The Moon is shedding material which makes a nice bright arc near the moon. That arc is about 150,000km (90,ooo miles) long or about one sixth the circumference of the circle. The moon is too small to see directly, only about 500 meters (1/3 of a mile) across. These images are 46 second exposures, so you can see the moon as a small streak (the other streaks are stars. You can see how much the moon and stars moved in 46 seconds. The camera tracked the rings so the rings would appear to stay still in the photos). For the record, Cassini took this image from a distance of about 1.2 million km.
Although it is very small, so small they sometimes call it a moonlet, it is a source of material for the G ring. But it might not be the only one. There is evidence other objects up to 100 meters across may reside in the G ring. Cassini will be making a close pass in 2010 so stay tuned for more.
Reprinted with permission from the Half-Astrophysicist Blog.
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7 comments:
61 moons! Wow! I knew Saturn had a lot of moons, but I wasn't aware of that many. Are they all named?
A 'g ring.' Interesting!
Hale-I did a little research here and there. I've noticed the use of shepherd moons. Why is that? Couldn't a gravitation pull or an orbit keep these rings in place?
Hey I just heard on the TV that a metorite or something came VERY close to earth recently and it could have been very bad if it hit us. It was closer than the moon. Did you hear about that?
A moonlet? Like a little baby moon. How cute.
Yes, Drew, shephered Moons help maintain the rings. Sometimes particles in the ring, through interactions with each other, either speed up a little bit or slow down a little bit which means they would leave the ring. As the shepherd moon passes by, the gravity from the moon will slow down the ones that are moving too fast and speed up the ones that are moving too slow keeping them in the ring.
Usually there are two shepherd moons, one on each side of the ring. Given that the ring is brighter and more dense near this moon, I am betting there is not a second moon large enough to act as a shepherd moon here. Particles from this moon are what supplies the ring with matter. As the little particles drift away from the moon, the density of the ring decreases since there is not a second moon to help maintain the integrity of the ring.
Thanks hale, that explains it!
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