Rings Discovered Around a Moon for the First Time

Riding with Robots writes "It turns out that one of the Ringed Planet's moons has rings of its own. The robotic spacecraft Cassini at Saturn has discovered that the icy moon Rhea is orbited by an extensive debris field and at least one ring, the first such system found. 'Many years ago we thought Saturn was the only planet with rings,' said one mission scientist. 'Now we may have a moon of Saturn that is a miniature version of its even more elaborately decorated parent.'"

Dumb question: Why are they 2 dimensional?

[guanxi]

You get used to seeing them and maybe don't question it, but why do so many structures in 'outer space' -- low gravity, three-dimensional space -- take on essentially two-dimensional forms? Consider rings around planets, planetary systems around stars, and galaxies, at least. They are all flat discs.

I asked an astrophysicist I know and she said, 'that's the way the math works out'. Ah, thanks. Maybe someone here can be more enlightening.

Disclaimer: For all you nitpickers, I know there are more than three dimensions, and that the structures are not truly two-dimensional. Unless string theory applies here, I think we can leave those facts out of the discussion.

Funny timing

[Brad1138]

Just last week my son said something that made me wonder, "could we put a satellite in orbit around our moon"?

Wow.

[Aegis Runestone]

That's really cool. I was so into the planets when I was young. Loved the Voyager missions (even made a model of the probe out of Contrux... and it was accurate too), and watched as many Nova specials about the Voyager missions as possible. That kid is not dead, he's just taken a place inside of me. I keep an occasional glance at the Cassini mission, just like the Galileo mission to Jupiter.

This is, indeed, a surprise discovery and hopefully there might be more material to study concerning this ring-type.

On a somewhat related-note: It is ironic that this moon has a ring whereas two moons hang out in Saturn's outer rings (they are called the Shepherd Moons).

Re:pff

[Brian Gordon]

It might not even be a ring at all..

Due to a decrease in the number of electrons detected by NASA's Cassini spacecraft on either side of the moon, scientists suggest that rings are the likeliest cause of these electrons being blocked before they reach Cassini.

Not very convincing.

Re:Funny timing

[Mantaar]

Yes of course we could. If you download Celestia [celestia.org] you can see all sorts of interesting things in space.
Now, my version is heavily modded (and it's the alpha version), but I can see Apollo still orbiting good ol' Moon in Celestia. And witness a nice dawn together with Apollo. *sigh* it's a pity that you go through that military drill to become an astronaut. I surely would like to be one.

Essentially, that's the same as putting a satellite around Earth, as Earth orbits Sun like Moon orbits Earth.

What's even more interesting: you could put a spacecraft in the Lagrange-point between Earth and Moon, so it wouldn't move - well with respect to Earth and Moon, of course.

Re:pff

[Tablizer]

Wake me up when they find a moon orbiting a ring.

Here ya go...well sort of:

http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2901 [nasa.gov]
   

Yeah, in mythology they were husband and wife

[dido]

You joke, but Saturn's (Cronus's) wife in mythology was named Rhea. A bit of a coincidence that.