LOOK TO SKIES FOR VIEW OF SATURN

The weather may not seem like fall, but leaving daylight savings time behind for earlier sunsets, stirs the fall astronomer blood in me. We have waited for some action in the sky all summer long and we are about to get a great treat.

After sunset, both Saturn and Jupiter come to join us from the east while Venus continues her slow climb out of the west. We have not really enjoyed the cool, clear, dry fall that we normally get, perhaps the weatherman will surprise us, I hope.

Since Saturn comes up first, we will focus on our ringed planet this month and save Jupiter for next month. Saturn is the second largest planet in the solar system. The fact that the beautiful ring system shares the view with cloud bands that are mild compared to Jupiter's, gives Saturn a calm, mysterious feel. The rings are rather sharply defined giving them a crisp appearance. Many people comment that it looks fake though a telescope.

Saturn gives off a little more heat than it receives from the sun. It is still warm from the time of its creation. Because of its gravity, the constant pressures heat the gasses just like the end of a bicycle pump gets hot after some use. It is so massive that all the heat has not yet escaped. But, by far the most impressive thing about Saturn is its rings.

From Earth-based telescopes, there are three well defined rings and astronomers, not wanting to waste all of their creativity naming them, call the rings A, B, and C. Between the B and C rings is a dark gap called the Cassini division. You can tell it is a gap because sometimes a star will pass behind the ring system and you can see it through the gap.

Cassini was a French astronomer who spent lots of time looking at Saturn and for whom the spacecraft Cassini is named. Cassini, the spacecraft, is heading for Saturn for a July 1, 2004 meeting. We should get some great photos of Saturn because the spacecraft is fully operational and ready to go.

As beautiful as the rings are, as scientists, we must explain their existence and characteristics. The rings puzzled astronomers for some time. We knew that they could not be solid disks but were made of smaller particles because different regions orbit independently with the inner regions orbiting the fastest. Yet, when the Pioneer spacecraft sent back the first close up pictures we were surprised to find not just three rings but thousands! Not just one gap but also thousands! How do you get rings anyway? You get rings by luring unsuspecting moons close to the planet. Because of Saturn's large mass, whenever you get close you experience strong tidal forces. The tidal forces are caused because the side of the moon facing Saturn feels a stronger pull from the gravity than the other side does. Thus the moon gets stretched out in an oblong shape. If you get too close, the strength of your rocks can't hold you together and you get ripped apart and form a ring. This is one of the reasons why physicists do not think we could ever survive a trip through a black hole.

The rings and gaps occur because the remaining moons exert a rhythmic pull of gravity that tends to pile material into rings and sweep them out of the gaps. These shepherd moons constantly tend their rings, keeping them in line, and producing one of the best free, visions in the universe. Enjoy.

Dr. Mike Cobb is chairman of the physics department at Southeast Missouri State University and can be reached at 651-2172.