Why are Saturn’s Rings Disappearing?

by Ian O'Neill on March 18, 2008

Saturns rings with Saturns moon Mimas in the foreground (credit: NASA)
Astronomers have noticed a change on Saturn. The planet’s rings are getting thinner and thinner and the details in the dark bands are getting harder to observe. What’s more, at this rate, Saturn’s rings will have completely vanished by Sept. 4, 2009!

But don’t pack up your telescopes quite yet, there’s no reason to be alarmed. This phenomenon occurs every 14 to 15 years and the explanation is down to an astronomical optical illusion called “ring plane crossing”…

In 1612, Galileo noticed something was awry with the beautiful gas giant. The distinctive rings of Saturn were shrinking until he was unable to see them any more. The situation was so strange that Galileo even stopped observing the planet (most likely through frustration!). He had discovered the rings two years earlier and was instantly entranced by them. He once wrote to his Medici patrons on the discovery in 1610: “I found another very strange wonder, which I should like to make known to their Highnesses…” so you can imagine his confusion when the rings slipped out of view.

Hubble Space Telescope observation of the side-on view of Saturn's rings during the last ring plane crossing in 1995 (credit: NASA/HST)

Ring plane crossings occur periodically when the tilt and position in Saturn’s orbit combine to allow astronomers a unique side-on view of the rings. Far from being a loss, looking at the paper-thin rings side-on will remove the glare from the bright rings giving astronomers a superb opportunity to see the icy moons orbiting close to Saturn. Also, Saturn’s strangely blue north pole should be observable. Saturn is better known for its brown-golden clouds of gas, but in high latitudes, these clouds thin out to reveal a blue dome. Cancelling the light from Saturn’s rings may provide a perfect environment to see the blue from Earth and to view the points of bright light shining off the small moons.

So dust off those telescopes, a once-in-14-year astronomical opportunity is approaching…

Source: NASA


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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

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