Word: solarization
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Dates: during 1990-1999
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...Leonids, so named because they seem to radiate from the constellation Leo, are actually debris shed by comet Tempel-Tuttle. In an elongated, 33-year orbit of the sun, the comet travels as far out as Uranus, then back to within 91 million miles of the solar surface, passing close to Earth's orbit on both its way in and its way out. Like other comets, Tempel-Tuttle is, in effect, a dirty snowball that heats up as it approaches the sun and boils off some of its "dirt," which consists largely of particles, some pea size...
Indeed, that is the situation this month. Tempel-Tuttle recently swept past Earth, swinging around the sun in February, and headed back toward the outer solar system. As a result, Earth will come within 700,000 miles of the center of the stream--a close shave by astronomical standards. And because Tempel-Tuttle orbits the sun in the opposite direction of Earth, the meteoroids will hurtle in at a closing speed of some 160,000 m.p.h...
...that velocity, says Guenter Riegler, a NASA senior scientist, a meteoroid as small as a dust particle could blast a hole nearly half an inch across in a solar panel or a layer of insulation. Equally threatening is the intense heat of impact, which would instantly vaporize the meteoroid and convert it to an ionized gas, or plasma, that would shock the spacecraft with an electrostatic charge. "If that charge got into some of your data circuitry," Riegler says, "it could wipe out data...
...Unlike an ordinary gas, the [outer atmosphere] of the sun that you see during a natural solar eclipse has a high degree of nonequilibrium," he said. "So every particle has its own temperature...
...Callisto were long suspected to bear icy crusts, but at a decidely chilly 483 million miles from the Sun, nobody expected these rocks to be anywhere near tropical enough for the liquid stuff. "If we find out four and a half billion years after the formation of the solar system that there's still enough heat that ice will melt on the interior of these bodies," said Margaret Kivelson, one of the researchers behind the study, "we have to do a little bit of rethinking...