A new ring around Uranus

By Phil Plait | December 22, 2005 10:06 pm

Sometimes, surprises await in your own back yard.

I’m not surprised new rings of Uranus were found when Hubble took another look at the gas giant. After all, it’s 3 billion kilometers away, and the rings are thin and faint. And actually, geometry is favoring them getting easier to see: as Uranus orbits the Sun, the rings get closer to being seen edge-on by us. Since they are so thin, this makes them easier to see, like how a transparent pane of glass gets easier to see as you tilt it.

No, what’s surprising about this new set of observations had to do with the moons seen along with these rings. What’s very interesting is that a moon discovered two years ago, called Mab, shares the same orbit as these rings. Now, you might think that a moon sitting in the middle of a ring would sweep up the dust in the ring, destroying it. But really, the fact that we see a ring at all means it must be coming from that moon, or related to it somehow.

But how? Well, enter surprise #2. These images have allowed scientists to track the orbits of these moons. They determined that the moons’ orbits are chaotic. That means that as the moons pass by each other in their orbits, they affect each other a lot, and it’s very difficult to predict how that will change their orbits in the future (we would need infinitely precise observations to make those predictions, which is of course impossible).

It also means that over millions of years, collisions are likely. The moons must smack into each other. What a sight that would be! The energy released would be awesome to behold!

And this might be the answer to the mystery of the moon in the ring: the moon might be the source of the faint ring, or, more accurately, both are related to the same event.

Imagine, a million years or so ago, as Mab (larger than it is now) orbits Uranus. Looming ahead is another moon… and they are aimed right at each other. They get closer, approaching at thousands of kilometers per hour. Then… kaBLAM! The collision would be more energetic than all the nuclear weapons on Earth combined. The catastrophe easily shatters the moons, creating millions of smaller moons a few meters to kilometers across. Too small for us to see, they would still be there orbiting Uranus today. What we now call Mab is simply the largest of those remaining chunks. The pulverized particles become the ring, and further collisions among the moonlets replenishes it.

When I was a kid, I thought Uranus wasn’t very interesting. I knew it was "lying on its side", but other than that very little was known by anyone. Ho hum! But I was wrong . There’s a lot going on out there.

All of this, I found, was the result of very short exposures of Uranus taken by Hubble. I’d love to see longer exposures taken (or in reality, more short exposures that can be added together) to see the rings and moons in more clarity. What other surprises await us in the solar system’s back yard?’

CATEGORIZED UNDER: Astronomy, Cool stuff, Science

Comments (13)

  1. Nigel Depledge

    Whoa! Isn’t science brilliant.

    I have to say, though, that my backyard isn’t as big as yours, Phil. I have backyard envy.

    I know what you meant, of course – compared to, say, Sirius, Uranus is really, really close. But it still took Voyager 2 nearly 15 years to get there.

  2. A new ring around Uranus, surprises await in your own back yard.
    I feel a joke coming on ;-)

    Fascinating to think of. Over the span of milions of years those rocks chipping away at each other, turning into finer and finer particles. It’s like a beach in space.

  3. storyville

    so what is the proper way to pronounce Uranus. “YourAnus” (with accent on the second syllable and a hard ‘a’ or “Yuriness” (with the accent on the first syllable and a softer ‘a’)?

  4. Carnifex

    storyville – isn’t it “You Rain Us”?”

  5. TRACY

    Thomas, when I read your comments I laughed so hard it hurt.
    Of course I was trying to formulate an appropriate joke when I read your comment. It’s going to be an interesting day to re-check this post!

  6. Richard Board

    I remember, many years ago, when Carl Sagan made one of his memorable appearances on The Tonight Show, Johnny Carson brought up the pronounciation of Uranus. It was at the time when the Voyager missions were beginning to make their first flybys of the outer planets and there was a lot of media attention being given to space science.

    Sagan, in his usual jovial and tongue-in-cheek style, admitted that the planet had been called “Your Anus” since its discovery; but now that there was so much mention of it on TV and radio, NASA officials had decided to try to stop the onslaught of predictable jokes by changing the pronounciation to “Urine-ess.” Too funny. I’ve had the pleasure of discussing this pronounciation dilemma with students of all ages. It’s always a hoot and the kids are invariably more curious about the cold, blue, tilted planet afterward.

    Who says science has no sense of humor?!

  7. TRACY

    I’ve always tried to read everything by Hawking, or at least the stuff I can understand without having a degree in physics. I think he has a great sense of humor, and anxiously await another lecture to be posted on his web site.

  8. I usually say it “Yuriness” very quickly and move on in the hopes that I don’t have to put up with the juvenile snickers. Gah, that irritates me. Maybe we think Uranus isn’t that interesting simply cause we don’t like talking about so as to avoid the giggling idiots.

    Regarding the possible collision of moons; how freaking cool is that? Why is it that all these intensely cool solar system shaping events happened millions of years ago? The closest thing we’ve had to this in our modern age was the comet impact on Jupiter. Dang, I want to see a moon collision too!

  9. Bad Albert

    You can hear the pronounciation on an audio file here at the Nine Planets website:
    http://www.nineplanets.org/uranus.html

  10. What? No mention of Klingons? :D

  11. tyler james mackhener jr
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