Date: March 8, 2009
Title: Where are Saturn’s Rings?
Podcaster: Ted Haulley
Description: People new to telescope viewing love to look at Saturn and the rings. In the International Year of Astronomy we are trying to get as many people as possible to look through a telescope, perhaps for the first time. A quirk of cosmic fate puts the rings edge on as seen from Earth this year, making one of the highlights of the sky a bit of an anticlimax. This episode will take a short look at the Saturn system to commemorate Saturn being on opposition on March 8.
Bio: Ted is celebrating the birth of his second child, a girl due the day his first podcast aired on February 15. Now a full-time student and Mr. Mom, Ted lives in Waldorf, Maryland with his wife Tammie and daughter Tanda. Ted can relate to first time viewers of Saturn. He bought his telescope in 1995, just in time to not see any rings around Saturn the last time they were edge on.
Today’s Sponsor: Anonymous
Transcript:
Hello, again. I’m Ted Haulley talking to you from Maryland, USA.
Most amateur astronomers love to share their interests with others. When someone uses your telescope for their first ever look through an eyepiece it gives you a special feeling. For some it may be the only time they will ever look through a telescope. So you want to give them a sight they will remember. One of the favorite targets of first time viewers is the planet Saturn. They have to see the rings for themselves. The awe in their voice as they look through the eyepiece lets you know that for at least a second, they understand why you spend so much time out in the cold and dark. Since we’re really trying to promote astronomy this year, we should take an extra effort to have as many first timers as possible get a glimpse through our eyepiece. Saturn is in opposition on March 8 this year, so it is visible pretty much all night through Spring. So your new viewers say they want to see Saturn. You point your telescope at Saturn, and let them have a look. You step back and wait for the reaction. “Hey! Where are the rings?” You’re left standing there stuttering, “Well, as Saturn orbits the sun the rings tilt in relation to the Earth and over a period of 15 years or so they go from edge on to open, and back to edge on as seen from the Earth, and right now we’re at a point in the cycle where the rings appear almost edge on. About 8 years from now they will be at the maximum tilt….” And your voice trails off, knowing that there is nothing you can say to recover the moment.
With so many anniversaries to recognize, this is a perfect year to celebrate astronomy. It is just a trick of the cosmos that one of the top sights may not be as appealing to first time viewers. Like the Griswolds in the movie “Vacation,” they get to Walley World, only to find it closed for repairs.
Many hard-core amateurs and professional astronomers actually look forward to the time when the rings go edge on. The rings reflect a lot of light, and the brightness of the rings can make it difficult to see dimmer things nearby. When all we had were Earth based telescopes, the edge on time was when we discovered new moons that normally could not be seen in the glare of the rings. It is also the best time to view the disc of Saturn itself.
Our friend Galileo first saw Saturn’s rings in 1610. The optics on his telescope was so poor that he could not make out exactly what they were. He said that Saturn had ‘ears,’ and his sketches showed Saturn being flanked by two large moons. When he looked at Saturn again in 1612, he was again amazed by what he saw. Nothing. The moons were gone. It just so happens the rings were edge on to the Earth, just like this year. So first time viewers of Saturn, take heart. Even Galileo was disappointed by the lack of rings. He encountered them a few years later, and he then described them as two half ellipses.
45 years later Christiaan Huygens finally determined that they were actually rings that circle the planet without touching it. He is also the one who discovered the moon Titan.
The rings themselves are actually individual particles of water ice, dust, and rock, ranging in size from a speck of dust to maybe up to a kilometer in length. When the Pioneer and Voyager spaceships made their flybys in the 70s and 80s, it was seen that each large ring is made up of smaller individual rings. The comparison at the time was the rings were like the grooves in a music record. Since we don’t really have those anymore, we may need to come up with a new analogy.
The main rings have really fancy names. We have the A ring, B ring, C ring, all the way up to the F ring. Of course they’re not in any order. That would be too easy. Starting inward and moving out, the rings are lettered D, C, B, A, F, G, E. They’re lettered in the order of their discovery.
At last count Saturn has 60 moons, including Titan which was thought to be the largest moon in the solar system. Only with the visits of Voyagers 1 and 2 in the early ’80s did that change. It turns out that Titan has an incredibly thick atmosphere, even thicker than Earth’s, and by removing the atmosphere from the measurements it is reduced to the second largest. Jupiter’s moon Ganymede is now measured as the largest. Just barely, though. Ganymede is 112 kilometers larger.
I mentioned that Saturn is in opposition on March 8. You may have heard the term before, but what the heck does it mean? Picture the solar system from above, and draw a line connecting the sun with Saturn or any of the other outer planets. At some point every year, the Earth will cross that line. When it does, that planet is in opposition: directly opposite the sun.
You may have heard that Saturn would float on water. It’s true. The density of Saturn is less than water, so it would float if you had a big enough bathtub. One last thing about the rings. You may have heard about how thin the rings are, but how thin are they? The main rings are perhaps 10 meters thick. To put that in perspective, if Saturn were the size of a football field, the rings would be the width of a razor blade.
Don’t let all this deter you from getting that look at Saturn. It is a good target for small telescopes, even in the most light polluted areas. Just keep in mind that Saturn will not look like the photos you are used to seeing. The rings go totally edge on in early September and until then, depending on your optics, you can still see a small line of rings. So if you’re disappointed with what you see in Saturn, remember that this is a special time. The rings are visible 14 out of every 15 years. Take the time to look at the planet itself. It’s the best look you’ll have of it until the next time the rings are edge on, in about 15 years.
So we’ve answered the question of where are Saturn’s rings? I’ll leave it to someone else to explain another common question asked by new viewers; “Why is everything upside down?”
I welcome all emails. Write me at Thaulley@yahoo.com. Thanks for listening.
365 Days of Astronomy
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