President Bernie Zelazny opened our meeting on March 17 at 7:30 PM in Room 206, Morelock Hall, on the Sul Ross Campus (because of Spring Break, our usual meeting room in Lawrence Hall was not available).  There were 14 people present.  Chuck Dobbins gave a program on Comets, amply illustrated with slides and figures (see description below).

           Comets have been widely misunderstood and feared in the past.  A comet in 1472, appearing at the same time as an occurrence of the plague, was blamed for bringing misfortune upon the people.
           Astronomer Fred Whipple has described a comet as a dirty snowball, a collection of ice, dust, and frozen gasses. The nucleus is composed of those materials, perhaps 1 to 50 km (1/2 to 30) miles in diameter. As a comet approaches the sun, some of the ice and frozen gasses melt, and are driven away from the comet, along with dust and various ions. Two distinct tails sometimes form, an ion tail and a dust tail, both pointing away from the sun. As a comet approaches the sun, the tail streams out behind. But when the comet turns around the sun, moving away from the sun, the tail then precedes the comet. Thus, it is the pressure of sunlight - not the motion of the comet - that causes the tail to stream away from the nucleus whether the comet is approaching or receding from the sun.
           Sometimes a comet develops an antitail apparently pointing in the direction of travel, along with an ordinary tail streaming behind the comet. If a dust tail and an ion tail are separated by a considerable angle - say, 90 deg, for example - if the comet is close to the sun, then we may see one tail behind the comet and the other apparently pointing ahead. Comet Arend-Roland once appeared with a sharp antitail.
           The coma is a glowing cloud of gas and dust that is driven off the nucleus when a comet is close enough to the sun.  The coma then surrounds the nucleus. A coma has reached a size of about 1 million miles. 
           The period of a comet is the time required to orbit the sun. For example, Comet Encke has a period of 3.3 years, and Halley’s Comet a period of 76 years. Halley’s was observed as early as 240 BC, and possibly as early as 1615 BC.
           A few years ago, Comet Shoemaker-Levy 9 broke into 22 pieces as it approached Jupiter. The comet fragments left impact craters on Jupiter ranging from about 300 to 18,000 miles in diameter. What would one of those large fragments have done to the earth?
 

           Once again dues are now payable for a new year, 2004. Maintaining a viable organization entails several ongoing costs, such as liability insurance, insurance on the Murray Newman Telescope, and mailing ex-penses. So please send in your dues, $20.00 per person, to:

           We need everyone’s support for the premier astronomical society between Odessa and El Paso, if not beyond.