Saturn and its rings visible again


Saturn is finally visible in the evening sky again and no night out under the stars is complete without a glimpse of those fabulous rings.

Saturn’s ring system is one of those few astronomical objects that even a dime-store telescope will show pretty well, so take a look.

You can start around 10:30 p.m. Saturn is decently above the horizon by then. Look for the pale orange “star” low in the south in the constellation Ophiuchus, The Snake Handler (no kidding). Look right above the far more familiar teapot-shaped constellation Sagittarius.

Saturn is about 890 million miles away from the sun right now, just less than 10 times the earth-sun distance. We can see it so well because the planet is so large. At 74,000 miles wide, it is more than nine times the diameter of the Earth.

Despite its size, the disk of the planet generally doesn’t show much detail in a telescope. The rings, however, are the finest sight in the cosmos.

We take the sheer beauty of the rings for granted, but up to a few hundred years ago, they were invisible to human eyes.

Ancient peoples noticed Saturn, of course. It was the slowest moving of the “wandering stars,” and the Greeks associated it with the King of the Titans, who ruled Olympus before Jupiter. His one great fear was that his children would overthrow him, so as they were born, he ate them!

In 1610, when Galileo first pointed a telescope at the heavens, it didn’t take him long to train his primitive instrument at Saturn, the farthest planet from the sun known at the time. But his telescope was tiny, with a light-gathering lens only one inch in diameter.

He couldn’t resolve the rings. Instead, he saw what he thought were two tiny balls touching the surface of the main disk. He concluded that Saturn was a triple planet.

Galileo was so afraid people would think he was crazy that he published his results as an anagram — words with their letters scrambled. He figured that if he were right, he would eventually get credit. If he were wrong, no one would be the wiser.

Two years later, he looked again at Saturn, and the companions had disappeared completely. Remembering the Greek story about Saturn, Galileo suggested that the Titan had eaten his own children!

As the century passed, telescopes got better. In 1655, Christiaan Huygens theorized that Saturn was surrounded by a flat, thin ring but was so overcome by the weirdness of the idea that he also published it as an anagram.

By 1665, most astronomers had warmed to the ring theory. In 1675, Italian astronomer G.D. Cassini discovered a gap in the ring structure, a dark line all the way around that divided the ring system in two.

We now know that the rings are over 220,000 miles wide around the planet, and they are less than a mile thick. They are made of mostly tiny particles of ice with a bit of dust mixed in. Only our distance from them makes them look solid in a telescope.

If the expansiveness of the rings doesn’t impress you, consider this: Saturn and its rings would just fit between our Earth and moon with very little room to spare.

But what of Saturn eating his children? It turns out that from our earthly point of view, the rings slowly tilt over a 29-year cycle, one trip by Saturn around the sun. For one season of the 29, the rings are tilted so that we see them edge-on, and they appear to our modern telescopes as a thin line.

In Galileo’s crude telescope, they appeared not at all.

Of course, people in Central Ohio have none of those problems. Here you can always count on Perkins Observatory’s big Schottland Reflecting Telescope to give you a view you will never forget.

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THEIR VIEW

Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.