Hailing Hale-Bopp.After a fallow spring in which its brightness and activity appeared to have leveled off, Comet Hale-Bopp seems to be living up to expectations that it will be the comet of the century when it nears Earth next March. That's the consensus of researchers who have tracked the icy body with a variety of Earth-orbiting and ground-based telescopes. Harold A. Weaver of Johns Hopkins University Johns Hopkins University, mainly at Baltimore, Md. Johns Hopkins in 1867 had a group of his associates incorporated as the trustees of a university and a hospital, endowing each with $3.5 million. Daniel C. in Baltimore is one of these optimists. He bases his enthusiasm on spectra taken over the past few months by the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. , the now-defunct International Ultraviolet Explorer International Ultraviolet Explorer: see ultraviolet astronomy. satellite, and radio telescopes on Earth. The spectra reveal that as the comet has journeyed into the inner solar system, it has begun to expel jets of water vapor. The vaporization vaporization, change of a liquid or solid substance to a gas or vapor. There is fundamentally no difference between the terms gas and vapor, but gas is used commonly to describe a substance that appears in the gaseous state under standard conditions of of water-ice has replaced that of carbon monoxide ice as the driving force behind the comet's growing brightness, Weaver says. At the same time, the comet is spewing more dust-to the relief of observers. Sunlight reflected off a comet's shroud of dust makes the icy body appear bright. The upswing in expelled dust, which is probably dragged out by the water vapor, should allay worries among amateur astronomers that Hale-Bopp, like the much-ballyhooed Comet Kohoutek in 1973, will fizzle, Weaver says. "It's really holding up pretty well," notes Brian G. Marsden Brian G. Marsden (born August 5,1937) is a British astronomer, the longtime director of the Minor Planet Center(MPC). He specializes in celestial mechanics and astrometry, collecting data on the positions of asteroids and comets and computing their orbits, often from minimal of the Smithsonian Astrophysical Observatory The Smithsonian Astrophysical Observatory (SAO) is a "research institute" of the Smithsonian Institution headquartered in Cambridge, Massachusetts, where it is joined with the Harvard College Observatory (HCO) to form the Harvard-Smithsonian Center for Astrophysics (CfA). in Cambridge, Mass. Nonetheless, cautions Michael F. A'Hearn of the University of Maryland University of Maryland can refer to:
Hubble won't be able to view Hale-Bopp again until next July, months after it nears Earth, because the comet will lie too close to the sun's glare. From Hubble images taken over the past year, Weaver estimates that the nucleus of Hale-Bopp measures a whopping 30 to 40 kilometers in diameter (SN: 12/23&30/95, p. 428). Other observed comets average, at most, 10 kilometers in diameter. Judging from the comet's recent activity and its considerable girth, Hale-Bopp "should be the most productive comet we have observed in modern times," says Weaver. Because the comet won't get any closer to Earth than 1.3 times the distance between our planet and the sun, it may appear only slightly brighter than last spring's Comet Hyakutake, he adds. Hale-Bopp will be most visible just after sunset in late March and April. Skywatchers, however, can already take a peek at Hale-Bopp with the naked eye for the first 3 weeks of this month. It appears just after sunset as a faint object in the southwest part of the sky, above and to the right of Jupiter. |
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