dipper@utastro.UUCP (Debbie Byrd) (09/04/85)
A comet passed in front of a bright star early this morning. More -- after this. September 4 Occultation by Giacobini-Zinner If all goes as planned, on September 11, the International Comet Explorer -- called I-C-E -- will become the first spacecraft ever launched from Earth to pass near a comet -- the Comet Giacobini-Zinner. Because of this upcoming mission, astronomers early this morning took a very special look at the comet -- as it passed in front of a star. This kind of event is called an occultation. In the occultation occurring early Wednesday morning, the light from a star in the constellation Auriga dimmed briefly as Comet Giacobini-Zinner moved in front of it. Both amateur and professional astronomers planned to observe this event. Many observers were needed -- since no one could be sure of where exactly in North America the occultation would be seen. Neither the star nor the comet are visible to the naked eye. But today's occultation is important because it'll provide information on the amount of dust surrounding the comet's nucleus, or core. NASA is especially interested in this comet's dust -- because the spacecraft heading for the comet was not originally designed for such a mission. There's no protection on the craft's solar panels -- the source of electricity for the spacecraft's scientific instruments. The dust from the comet could so heavily damage the solar panels that the spacecraft's instruments would turn off. So today -- as Giacobini-Zinner passed in front of a star -- astronomers tried to measure both the extent of the dust cloud -- and the exact position of the comet. Final course corrections are due later this week -- as NASA's spacecraft I-C-E makes the world's first encounter with a comet. Script by Diana Hadley. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin