Word: halley
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There are good reasons for this intensive scrutiny. To astronomers, a comet is a sort of flying museum stocked with precious artifacts from the very earliest moments of the solar system. They hope that by peering into Halley's cold heart and sniffing out the dust and gases that stream from its surface, they can discern the conditions that existed at the birth of the sun and the nine planets some 4.5 billion years ago. That in turn could reveal how common an occurrence the formation of planets around other stars may be, hence how likely it is that extraterrestrial...
Still, the mounting mania greeting Halley's return has less to do with science than with the comet's reputation as a fiery harbinger of doom and its familiar role in presaging such events as the fall of Jerusalem in the 1st century or the Norman Conquest (see box). Indeed, for the public as well as scientists, 1986 may turn out to be the Year of the Comet. "The arrival of Halley's comet is not just an astronomical event," insists Joseph Laufer, ^ editor and publisher of a three-year-old Halley's comet newsletter. "It's a cultural event...
...reappears every 3.3 years), insisted that the orbit of "his" comet could not be explained solely by gravity. He proposed that "ether," an invisible theoretical substance that at the time was believed to pervade space, exerted drag on the nucleus, slowing it down. After observing flares streaming from Comet Halley's surface in 1836, another German astronomer, Friedrich Wilhelm Bessel, conceived a more plausible concept, the fountain theory. Bessel proposed that a comet was a loose clump of particles. He suggested the flares were fountains of these motes erupting from its nucleus and that they acted as a brake. Bessel...
...nucleus beneath. For every revolution a typical comet makes around the sun, its diameter is estimated to shrink about 6 ft. Hence the original size of the comet, the length of its orbit and how close it gets to the sun will determine its life-span. Astronomers estimate that Halley's, which has a relatively short period, will probably last another 225,000 years, a mere wink of astronomical time...
...most important contributions from the Vega program will be what is called the Pathfinder concept. Together the probes will attempt to reckon the position and orbit of Halley's nucleus with a precision impossible from ground-based observations and then beam the data back to the Soviet Union, which will in turn relay the information to European mission control in Darmstadt, West Germany, in time for Giotto's rendezvous on March 13. Precision is of the essence: zeroing in on a nucleus that scientists estimate measures only two to six miles in diameter and is traveling some 154,000 m.p.h...