Word: halley
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Dates: during 1980-1989
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...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...
...five. Looking rather like an oil drum with an upended beach umbrella stuck on top, the 5-ft. by 6-ft. probe was launched from Kourou, French Guiana, last July; as of last week it was 21 million miles from earth and nearly three times as far from Halley's. The little ship and everything on it are built for survival, and with good reason. The dust particles around the nucleus are expected to strike Giotto with such great velocity that a speck weighing a tenth of a gram would penetrate an aluminum plate about 3 in. thick. To prevent...
Indeed, superstition about comets has persisted into the 20th century. As Halley's came into view in 1910, some residents of Chicago prepared themselves for death by cyanogen-gas poisoning when, as it was widely predicted, the earth passed through the comet's tail. As recently as 1970, Vietnamese peasants quaked at the sight of the "Sky Broom," the unexpectedly vivid passage of Bennett's comet...