Reveling in Saturn’s beauty


By Tom Burns - Stargazing



What stargazer, expert or novice, does not feel a thrill of anticipation as a telescope slowly turns to Saturn?

The ringed planet is visible again in the morning sky, and thousands will revel in its beauty over the next few months as it slowly migrates toward the evening.

If you want to be one of the first round of revelers, look south about 5 a.m. Saturn will appear to the unaided eye as a bright, orange point of light just to the left of the teapot-shaped stars of the constellation Sagittarius, the Archer. Much brighter Jupiter is slightly up and to the right. The close conjunction of the two planets is of some significance, as we shall see, if you happen to know the old Greco-Roman myths about the stars.

As the weeks pass, the planets will rise earlier each day. By summer, they will be visible in the early evening just after dark in the southern sky.

Long lines will form at summer stargazing programs, so plan to arrive early. If any single event could be said to convert individuals to a lifetime of stargazing, one glimpse of Saturn’s rings will do the trick.

Saturn is about 80 million miles away from the sun. 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.

In 1609, 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 an old 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 directly observed the structure as a flat, thin ring but was so overcome by the weirdness of the experience 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. The number of rings increased slowly as telescopes got better.

In 1787, Pierre-Simon Laplace proposed that the rings were made up of many solid ringlets. They would have to be spinning rapidly around Saturn or Saturn’s gravity would make them collapse into the planet.

However, in 1859, James Clerk Maxwell proved that solid rings in rapid rotation would simply tear themselves apart. Instead, he suggested that the rings had to be made up of an enormous number of small particles, tiny “moons,” all of which were independently orbiting Saturn. In 1895, spectroscopic analysis of the rings proved that Maxwell was right.

We now know that the rings are about 235,000 miles wide around the planet. Saturn and its ring system would just fit between the Earth and its moon.

Yet at their widest, they are no more than half a mile a thick, and in some places, they are no thicker than 10 yards or so. They are far thinner than a sheet of paper if you scaled it up to ring size.

They are made of mostly tiny particles of mostly water ice with a trace of rocky material mixed in. In other words, they are like the dirty hunks of ice you might find frozen to your car’s wheel wells.

The individual ring particles, trillions of them, are all rotating rapidly around the planet. Because they are 800 million miles away, we see them as a solid ring. Distance alone creates the illusion of a solid ring.

What looks like a single ring is really hundreds of thin concentric circles. A medium-sized scope at higher magnification will show Cassini’s Division, the widest division in the rings, about halfway from the planet.

Even the Cassini spacecraft, which was in orbit around Saturn from 2004 to 2017, could not resolve the rings into particles. However, when the Voyager I spacecraft did its flyby of Saturn in the early 1980s, it passed through one of the outer dusty rings. I will never forget hearing the sizzling sound of innumerable tiny particles hitting the hull of the spacecraft as it zipped past Saturn.

But what of Saturn eating his children? It turns out that from our earthly point of view, the rings slowly tilt over a 15-year cycle, one trip by Saturn around the sun.

For two seasons of Saturn’s 29-year orbit, the rings are tilted so that we see them edge-on, and they appear to our modern telescopes as a thin line. Every 15 years or so, we see them tilted so that they appear almost “face-on” in all their glory.

We have known those facts for only a short time. Ancient peoples noticed Saturn, of course. It was the slowest moving of the ”wandering” stars.

Thousands of years ago, the Greeks and Romans worshipped Saturn as Father Time, the King of the Titans. To the Romans especially, he was the god of agriculture and ruler of the universe. He introduced the art of farming and thus brought civilization to the world.

The result was a golden age, a time when humans lived like gods and death was no more than sleep.

He was honored in a weeklong festival called the Saturnalia, which was kind of like spring break in Cancun but celebrated at the end of the year. The Romans took the week off to drink and carry on.

Saturn’s reign ended soon after the birth of his son Jupiter. It had been prophesied that he would be deposed by one of his sons.

To forestall his overthrow, Saturn began swallowing his children at birth. After the fifth child, his wife tried a bit of trickery to save the sixth.

When she gave birth to Jupiter, she wrapped up a rock and presented it to Saturn as the boy. He swallowed the rock and was none the wiser, except maybe for a severe case of indigestion.

When Jupiter grew to manhood (in his case, godhood), he tossed Saturn into Tartarus, the dark region below the Earth, where he still lies imprisoned. In an alternate version of the story, he cast him into the outer darkness, where we see him as the planet Saturn to this very day.

Jupiter took over, and the world turned into the mess we have today.

I’ll grant that nobody believes in Father Time anymore. But as the old year ends and the new one begins, we celebrate our own version of the Saturnalia with drink, dance, and song. We don our party hats like laurel wreaths and forget about our problems.

And as the new year begins, old Father Time must pass on the mantle of his rule to his baby son and is thus destroyed.

Thus, as the ball drops on New Year’s Eve, Saturn still reigns, if ever so briefly, over the rhythm of our modern world.

For an old stargazer like me, Saturn has a very personal dimension. I have been chided by astronerds far astronerdier than I for telling the old stories about the stars and planets. “Get real,” one of them said. “I want to know what’s really happening.”

As I gaze at Jupiter and Saturn in the morning sky, I am reminded of an evening back in 2017. As I looked at the rings in their full, face-on glory, I thought about the 15-year ring cycle. In 2025 they will be edge-on again. In 2032, they will be fully face-on again. How many such cycles have I been witness to? How many …? Wait.

I was 65 years old that night. I will be 80 when the rings are face-on again. Will I still be on the planet in 2032? Will I live to see the rings in all their glory again?

Or will I, like Saturn, by then be cast into the outer darkness? At that moment, the view of Saturn’s rings became more precious than mere words can say.

But I’ll try anyway. I knew, at least as far as an old English major can know, the science of the rings and their rhythmic openings and closings. But I also knew the old story of Saturn and Jupiter. For that reason, I could, at that soul-rending moment, look into the ancient eyes of Father Time as we stood toe-to-toe in the outer darkness.

And, oh, my dear friends, nothing is more real than that.

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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.