Saturn the Incredible Planet

© 1988, 2002 by Robert C. Moler

"You've got a slide in here! Right?" is a comment often heard When the observatory telescope is pointed to Saturn on a public viewing night. We say that they are looking at Saturn 'live', or at least as of an hour ago. That's how long Saturn's reflected sunlight takes to reach the earth.

Saturn is an amazing planet. Once thought to be the only planet with rings, its stature hasn't diminished with the discovery of Jupiter's, or Uranus' thinner rings, or Neptune's partial ringlets. None of these ether planetary ring systems holds candle to the broad ring system that can be seen in any small telescope.

The earth and Saturn have something in common. They appear the some size when viewed from the sun. Saturn is 9.5 times farther from the sun than the earth, and is 9.5 times larger in diameter. That means Saturn gets the same amount of heat and light from the sun that the earth does, hut its diluted by a factor of 90 times (9.5 squared) following the inverse square law of light propagation.

Saturn orbits the sun not in the majestic Slowness of Jupiter's 12 gear orbit, but with the geriatric shuffle that takes it nearly 30 years to complete its circuit of the sun. Thus it was named after the Roman god of old age, Saturn, commonly pictured as Father Time.

Saturn's equatorial diameter is 74,500 miles, its polar diameter is shorter by 8,300 miles due to its rapid spin. Its day is only 10.65 hours long. Its atmosphere is mostly hydrogen with methane clouds and ammonia crystal clouds. The haze of the ammonia clouds obscures the very active banded structure of the lower clouds which would look more vivid than those of Jupiter. Through the telescope a dark equatorial band can usually be seen.

The rings of Saturn are more reflective than the planet itself. They look white to Saturn's creamy yellow. Saturn's rings are made of familiar material; ice. The rings aren't solid, hut made of a huge number of particles in independent orbits of Saturn. The sheer numbers of particles and constant collisions keep the ring particles confined to a very narrow plane. For their breadth of 175,000 miles they are probably less than a mile thick, and maybe less than that. Saturn has three distinct rings that can he seen with small telescopes. They are labeled form outside in: A, B and C.

The A ring is separated by the broad B ring by a dark gap that's 3,000 miles wide called the Cassini Division after Domenico Cassini who discovered it in 1675, The C or Crepe Ring is best seen as a dim veil against the background of the planet. a good test of a telescope's quality, steady skies and an observer's skill is in seeing Cassini's division and the Crepe ring. Also seen are the shadows of the rings on the planet and the planet on the rings. One of our former members the late Stewart Taylor did an important study of the geometry of the shadows in the 1920's. Currently the rings are near their fullest appearance. The rings orbit the planet over the equator, and Saturn's axis is tilted some 26 degrees to its orbit. of the sun. The rings were edge on in 1995 and will be half an orbit later in 2010. We are (2002) nearing the intervening maximum tilt. When the rings are edge on the completely disappear, which was an earIt clue to their thinness.

Another feature of Saturn is its sgstem of satellites. Saturn is probably the satelllite champion of all the planets even discounting ring particles. Currently It leads Jupiter by a satellite count of about 30 to 19. Even better for the amateur astronomer, more of Saturn's satellites are within reach. Other than the big four Galilean satellites, Jupiter's other moons are tiny. Five of Saturn's moons can easily be spotted.

So the answer to the opening question is no. In fact I've never taken a photograph of Saturn that comes anywhere close to capturing the splended sight of it in the telescope eyepiece.


Questions? Send Email to me at bob@bjmoler.org

Updated: 02/04/02