Saturn is back in our early evening sky, thank goodness. Nothing beats the view of the planet’s rings in even a small telescope.
To find it, look low in the south just after dark. You’ll see a relatively bright point of light shining with a steady, yellow glow.
The seventh planet from the sun is 840 million miles from Earth right now. The light you see took almost 75 minutes to travel to your eyeballs on Earth.
The planet proper is 75,000 miles wide, and the rings’ visible portion spans perhaps 220,000 from tip to tip. Saturn and its rings would just barely fit between the Earth and Earth’s moon.
In a sense, Saturn doesn’t have rings at all. It has a billion trillion tiny moons, or rather moon fragments, that orbit the planet along the same plane. The ring system, or rather the ring plane, may have a large diameter, but it is exceedingly thin at only a mile or so wide in most places.
While looking through the Perkins telescope one night, a pugnacious 10-year-old commented, “Hey! I only see one ring. Rip off!”
Yes, my friends, there is hope for America’s youth. The “rings” look like a single ring most of the time.
However, look carefully at the ring if you have a large telescope (or visit a public program at Perkins Observatory or the John Glenn Astronomy Park). You just might see a thin, dark line running all the way around the ring, looking much like a division in a phonograph record.
(If you’ve never seen a phonograph record, please consult the collection of Strawberry Alarm Clock records in your parent’s or grandparent’s attic. Then ask yourself what your parents were really like at your age.)
You’re looking at Cassini’s Division, the first of many gaps in the ring discovered as telescopes became more powerful over the decades. As it turns out, Saturn has thousands of these concentric divisions, but you’ll need a spacecraft cruising by the planet to see them all.
In fact, the first views of Saturn revealed no rings at all. In 1609, Galileo, who first looked at the planet with a tiny telescope, thought he saw a lump on each side of the planet’s disk. He hypothesized that Saturn was a triple planet or an early advertisement for the Mickey Mouse Club. I can’t remember which.
Okay, okay, I’m kidding. Walt Disney didn’t invent Mickey Mouse until 1923. The inescapable fact is that it took one of the greatest astronomical geniuses of all time to allow humans to see the rings.
Christiaan Huygens was a Dutch astronomer, mathematician, optician, lens grinder, clockmaker, and physicist. The guy just couldn’t keep a job.
During the mid-1600s, he decided to improve on the terrible quality of the telescope lenses of the time. By 1655, he had produced a lens of such great clarity that he discovered Saturn’s largest moon, which he called Titan.
In Greek mythology, Saturn was not, strictly speaking, a god but a titan, which shows that Huygens knew a bit about ancient mythology, among his many other accomplishments.
He began creating lenses of such high magnification that they had to be placed in tubes as long as 23 feet. Those instruments were awkward to use. They were suspended from ropes on tall poles, and it took Zen-like patience to keep them pointed.
And yet he did so, hour after hour, night after night. By 1658, he made the discovery for which astronerds around the planet most often remember him. Saturn, he wrote, “is surrounded by a thin, flat ring, nowhere touching.”
Of course, no one believed him. This supposed revelation was weird beyond belief. Huygens persevered, however. By carefully calculating the motions of Earth and Saturn, he predicted that in 1677, the ring would be so inclined that astronomers would see it edge-on.
He also predicted that the ring is so thin that telescopists might not be able to see it at all. As astronomers trained their telescopes on the planet during the summer of that year, they discovered that the ring was gone!
Weirdness compounded upon weirdness, but one thing was certain. The great Christiaan Huygens was right.
Tom Burns is the former director of the Perkins Observatory in Delaware.
