Saturn, the gorgeous gas giant, flashes its rings

Gaze at the moon through a telescope and you will remark on how sharp the lens is. Look at Saturn, and you will forget the telescope altogether, too in awe of the glowing halo girdling the planet.

For me, astronomy began when I saw Saturn through my wife's 8-inch Dobsonsian reflector.

Prior to Galileo, Saturn was the most distant planet humans could see. Neptune, Uranus, Pluto, were invisible to the unaided eye. In 1610, the Tuscan inventor recorded seeing some "bumps," a bulge around the middle of the planet. But his instrument's resolution was not powerful enough to distinguish the rings.

The Dutch astronomer Christian Huygens, with a more powerful telescope than Galileo, first saw the rings in 1659. Fascination with Saturn has not ceased since.

Astronomers estimate that the total mass of the rings, if crunched into a ball, would make a satellite 180 miles in diameter. They are astonishingly thin – a mere 30 to 50 feet in some places. Their width is a little less than 300,000 miles, but highly reflective – visible to us from a distance more than six times the distance Earth is to the sun.

Eric Chaisson, who teaches astrophysics at Harvard and was a member of the design team for the Hubble telescope, says of the rings in his astronomy text "Astronomy Today": "Stars can occasionally be seen through them, like automobile headlights penetrating a snowstorm."

Contemplating the presence of the planet in the heavens, two questions simultaneously arise: What are the rings made of? Why don't they spin off? The first is easier than the second.

Saturn's rings are not one continuous band of matter, extending like the brim of a hat pulled down low over the head. They are not solid, gas, or liquid. In 1857, the Scottish physicist James Clerk Maxwell did the math and showed that they were most likely small particles, all independently orbiting Saturn, as if each were a tiny moon. In 1895, astronomers at the Lick Observatory, east of San Jose, Calif., confirmed this theory.

Since they reflect most (more than 80 percent) of the sunlight striking them, astronomers deduced that they were primarily made of ice and dirt particles – which we now know they are.

Where they come from and how they stay hitched to Saturn is another matter, and beyond the ken of this column. (All of the giant gas planets, Jupiter, Neptune, Uranus, have rings, but none are as pronounced, or as visible, as Saturn's.)

In simplest terms, the complex gravitational pulls among Saturn, the particles, and some of Saturn's 30 moons keep the seven bands of rings in place. It also creates the gaps between the rings. (The best known and largest gap is the Cassini Division, discovered in 1675 by the French-Italian astronomer, Giovanni Cassini. Saturn's tiny moon Mimas is responsible for clearing out the material creating a space – what appears as an empty orbit – about 3,200 miles wide.)

There are two leading theories about the origin of the rings: The particles are made up of material present at the formation of Saturn 4.3 billion years ago; they are gravitationally bound debris from former moons that collided with comets captured by Saturn's gravity.

Recent data, especially from Voyager 1 and 2, suggest the rings are no more than 50 million years old, giving weight to the second theory that they are captured material from a comet or comets colliding with one of Saturn's moons.

In the next two months, the gas giant that takes 29 Earth years to orbit the sun will reach its maximum tilt (27 degrees) relative to Earth. That means Saturn's rings will present the greatest viewing surface.

In the northern hemisphere, the better times to see Saturn in October will be after 11 p.m. Early in the morning, after 2 a.m., is best. Move those times up an hour for November.

When there is no moon, Saturn will be the third-brightest object in the sky with Sirius the brightest, and then Jupiter.

To find Saturn, look for Orion's belt in the east, go northeast to the red giant star, Betelgeuse, in Orion's shoulder, then the same distance again northeast to the hunter's club, where Saturn will sit.

Nights where the moon will not be a factor, allowing clearer views of the rings, are Oct. 2-13, Oct. 29 to Nov. 11, and Nov. 26-30.

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