Burns: Saturn’s rings finest sight in cosmos


By Tom Burns - Stargazing



No night out under the stars is complete without a glimpse of the fabulous rings of the planet Saturn.

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 9 p.m. during deep evening twilight. Saturn is decently above the horizon by then. Look for the pale orange “star” low in the south in the constellation Sagittarius, the Archer. Look up and to the left of the teapot-shaped group of stars that form the main body of Sagittarius.

Alternatively, Saturn is hard to miss if you look just before the stars begin to pop out of the advancing twilight. When you look south, you see brilliant Jupiter. Trailing it to the left is much-dimmer Saturn.

Saturn is about 850 million miles away from the sun right now, a bit more than nine 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. Its very reflective ring system spans about 220,000 miles.

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.

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.

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 1 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 a Greek story about Saturn (see below), Galileo suggested metaphorically 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 visible 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.

Spacecraft images show that the ring is really thousands of concentric rings pulled into place by the gravitational effect of larger hunks of material in and embedded between the moons. They are quite appropriately and poetically called Sheppard moons.

What caused the rings in the first place is still something of a mystery to astronomers despite the visits of several spacecraft to their environs.

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. Every 14.5 years, 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.

In the Perkins telescope, we lose the rings for three or four nights out of 29, but I directed the observatory long enough that we lived through a ringless Saturn twice during my tenure.

We had a group of 90 Cub Scouts one of those nights. The Scouts had been elevated to an astronomical frenzy by their leaders. They were going to have a truly once-in-a-lifetime look at the rings! Of Saturn!

As it turned out, they had a truly once-in-a-lifetime look at Saturn without the rings.

They were not impressed. I was, however. Where had those young lads learned such colorful language?

Of course, people in central Ohio have none of those problems. Here’s hoping that someday soon you will be able to visit Perkins Observatory’s big Schottland Reflecting Telescope again and revel in a view you will never forget.

Long before the invention of the telescope, 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!

One such is old Father Time, whom we see mostly on New Year’s Eve, sickle in hand, passing on the burden of the coming year to the New Year’s baby.

Father Time is older than you might think. He has moved slowly and inexorably across the sky for eons. As August marches forward into September, you may see him, much as our ancient forebears did, marking the passing of the days, months and years.

He is Saturn, the god of time and agriculture. He is visible in the early evening as a bright, orange-yellow point of light low in the southern sky.

He is hard to miss because he is preceded by bright Jupiter. During evening twilight before the stars come out, look for bright Jupiter low in the south. Saturn will be off to the left.

It takes a small telescope to see its fabulous rings. Sadly, you won’t be able to attend the weekend programs at Perkins Observatory or the John Glenn Astronomy Park until the current health emergency subsides.

But find some way to see it. Ask any lifelong stargazer what keeps them enamored of the nighttime sky, and they will recount to you in vivid detail the first time they saw Saturn in a telescope.

Because Saturn was the slowest moving of the planets visible to them, the ancients saw it as a symbol of the slow passage of the years. The Greeks called it Cronus, Father Time, the father of all the gods on Mount Olympus.

He was also in charge of fertility. He made the plants and animals grow and multiply, passing their seed on through time into the next generation.

That’s why, to this day, Father Time still carries his scythe, ready to harvest the Earth’s bounty.

Cronus was not, strictly speaking, a god but a titan, the beings who ruled the universe before the gods came to power.

He came to power by driving out his father, Uranus, the god of the sky, with his sickle.

Having heard a prophecy that he, in turn, would be deposed by one of his own children, he swallowed them whole as they were born.

The only child to escape Cronus’ weird culinary habits was Zeus, called Jupiter by the Romans.

He was smuggled by his mother, Rhea, to the island of Crete, where he grew to manhood.

Cronus was tricked into vomiting up his other children, and they joined forces with Zeus to overthrow their father.

After a 10-year war, Zeus and the other gods were triumphant. In one version of the myth, they threw Cronus into Tartarus, the deepest bowels of the earth, below even Hades.

In another version that matches what we see in the sky, he was cast into the outer darkness beyond even Jupiter. There, he moves quite ponderously across the sky and contemplates his misdeeds.

For all his faults, Cronus was a kind and gentle deity. His rule brought a golden age to Earth — a period when time and nature were bountiful. The crops grew without fail, and time moved with the slow softness of a summer breeze.

Humans lived like the gods themselves, and even death was no worse than a gentle dream.

With his banishment, the age of death and change began. The age of the gods came, and human fate moves now with their fickle whims. (Try living in your father’s stomach for a while and see what it does for your disposition.)

Crops sometimes are bountiful, and sometimes they fail. The seasons are inconstant, and death is the inevitable end of life.

The old gods and titans are gone now. We see their ghosts as those bright points of light, the planets, that wander slowly among the stars.

Perhaps you will think of Cronus as you look at his rings with your telescope this summer. He wears them low on his head like a triumphant wreath of golden ivy.

It is well that he should be so crowned. In a sense, Father Time still rules. We are still bound by the brief years we dwell upon our planet, by the inexorable flow of time in our all-too-brief residence here.

Time, Cronus’ gift to the world, is still our greatest joy — and our greatest sorrow.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.