Comet Hale-Bopp Puts on a Show
Thomas Bopp is a big, broad-shouldered man with a deep voice, a quiet demeanor and a look on his face that suggests he would like to get this experience over quickly. The 47-year-old amateur astronomer from Phoenix, Ariz., is speaking to about 150 people at the Ontario Science Centre in Toronto about the night in July, 1995, when he peered through a friend's 45-cm home-built telescope and spotted a fuzzy little object unlike the surrounding stars. It turned out to be a COMET - one that could produce a spectacular celestial show over the next few weeks. "I never seriously thought I would find anything like that," Bopp, an unemployed retail manager, says during an interview. "The chances of me discovering a bright comet, something that occurs once every 20 years or so, were astronomically small."
Comet Hale-Bopp as it is known - professional astronomer Alan Hale observed it on the same July night from his backyard in Cloudcroft, N.M. - has been visible to the naked eye since early in February in the eastern sky just before sunrise. If it lives up to its potential, this chunk of galactic ice and dust, which is thought to be about 40 km across, could attain a shimmering brilliance in late March and early April, and then remain visible all night for several months. "I see little reason to change the position I took at the beginning of August, 1995, that the comet will perform superbly," says Brian Marsden, director of the Central Bureau for Astronomical Telegrams in Cambridge, Mass., the agency that records and names all discoveries. "I honestly don't see how it can fail us."
Its performance so far has certainly been impressive. Calculations show that it was in the neighborhood of Jupiter, more than 600-million km from Earth, when Hale and Bopp first spotted it. Since then, Hale-Bopp has dazzled the astronomical community as it hurtled hundreds of millions of kilometres through space towards the centre of the Solar System. "This one is quite beautiful and has the potential to be quite bright," says the Arizona-based writer and amateur astronomer David Levy, an ex-Montrealer who co-discovered a comet that slammed into Jupiter in July, 1994. "It's very active under the telescope. It's spouting jets of dust and gas just like a volcano."
This comet, like all others that orbit the sun, was shaken loose at some point in the cosmic past from a ring of debris - scraps left over from the Big Bang - that surrounds the Solar System. Since then, it has been following a long, wide path that takes it out beyond Pluto and then back towards the sun. The comet last passed by the Earth 4,200 years ago, says Marsden, about the time that ancient Chinese emperors began hiring court astronomers to record unusual celestial events such as eclipses and the appearance of comets - although there is nothing in their records to suggest that they saw Hale-Bopp. They had no scientific explanation for the celestial visitors, interpreting them instead as signs of impending misfortune.
On this pass, Hale-Bopp will reach its closest point to Earth - 190 million km - on March 23. By comparison, Hyakutake, a comet that was visible to the naked eye for about a week in late January, 1996, came within nine million kilometres. But because of its enormous size and volatile makeup, Hale-Bopp could put on a much more impressive show. Observers say the comet already has a spectacular tail - a shimmering stream of dust and ice particles possibly as much as 50 million km long. Heat from the sun appears to be continually unleashing material from its core. "As the nucleus rotates and certain active areas are exposed to sunlight, they start erupting," says Levy. "They produce magnificent jets. It doesn't take much to get them going, just a little bit of sunlight."
But for all the anticipation surrounding Hale-Bopp, many astronomers, professional and amateur, are keeping their enthusiasm guarded. Other comets, after all, have arrived in Earth's neck of the Solar System laden with great expectations, only to fizzle. As close as it was in celestia