Blue Jay, Vol.54, Issue 3

Astronomy COMET HALE-BOPP — 1997’s BIG EVENT? STANLEY SHADICK, Department of Physics, University of Saskatchewan, Saskatoon, SK. S7N 0W0 The following article is adapted from frosty missiles into the inner region a selection in the 1997 Canadian of our solar system. The gravitational Skywatcher’s Trivia Calendar, written tug of an occasional passing star by Stan Shadick and published by may also divert a few. Fifth House Publishers (1-800-360- 8826). As they approach on long, elliptical orbits, the warmth of the sun vapor¬ Way out beyond Pluto’s orbit, a izes cometary gases that have laid vast swarm of icy comets slowly orbit dormant in a frozen state for billions our Sun. These dirty snowballs rep¬ of years. The released gases and resent debris left over from the disk dust particles form long, arched tails of gas and dust that formed the plan¬ that may extend as far as the Sun’s ets, 4.5 billion years ago. Occasion¬ distance from Earth. The early ally, tides, generated in this swarm Greeks described such phenomena by the collective gravity of numerous as “kometes,” meaning long-haired, distant stars, divert a few of these Position of Comet Hale-Bopp during January and February. 156 Blue Jay from which our word comet is ancient fear of comets was not too derived. far off the mark. Prior to its 1910 return, astrono¬ The close approach of a comet to mers predicted Earth would pass Earth creates the greatest spectacle through the low density tail of Hal¬ of the nocturnal skies. Only a few ley’s comet. Newspaper writers cre¬ such displays occur in a lifetime of ated a sensation after reporting that observation. The 1910 appearance poisonous cyanogen gas could be of Halley’s comet was preceded by present in the comet’s tail. Even an even more spectacular comet, a though the density would be too low few months earlier. Halley’s return in to have any adverse effects, some 1986 was a disappointment by com¬ people panicked. Charlatans made a parison, as it passed on the far side killing selling comet pills (made of of the Sun. The last dazzling comets sugar) to protect the frightened pub¬ to grace our skies were Comet West lic from such cometary gases. in 1976 and last spring’s magnificent Comet Hyakutake, which passed Ancient superstitions held comets within 15 million km of Earth. to be evil omens. The death of the Roman Emperor Macrinus was On the night of 23 July 1995, two blamed on the sighting of Halley’s amateur astronomers, Alan Hale and comet in 218 AD. While dismissing Thomas Bopp discovered a comet to such alarmist propaganda, some sci¬ rival Hyakutake. If it lives up to ex¬ entists suspect that a collision of a pectations, Comet Hale-Bopp may comet with our planet may have dominate the dark evening skies of killed off the dinosaurs, 65 million March and April as it passes within years ago. In July 1994, the world 200 million km of Earth. The follow¬ watched Comet Shoemaker-Levy 9 ing charts will help you follow its crash into Jupiter. Perhaps the approach. Position of Comet Hale-Bopp during March. 54(3). September 1996 157 The first chart shows the position Bopp makes its closest approach to of Comet Hale-Bopp during January Earth on 22 March, when its distance and February as it traverses the is only 197 million km. The comet eastern sky, 90 minutes before sun¬ should be at its best during the last rise. As the year begins, the comet is week of March, since moonshine will still 380 million km from Earth. The no longer interfere with observations. view will improve through February as the comet’s distance decreases. After passing the Sun on 31 March, Comet Hale-Bopp will remain The second chart follows the visible throughout April. Its position in comet’s path through March as it April is illustrated in a full colour map, moves into the northwestern evening found in the Canadian Skywatcher’s sky, 90 minutes after sunset. Hale- Trivia Calendar. Prairie Rattlesnake Wayne Lynch 158 Blue Jay .

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