Word: solar
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Dates: during 1980-1989
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Like dancers in an intricately choreographed ballet, each craft will perform a variety of tasks, complementing and aiding one another every thrust of the way. Japan's two probes, Sakigake (Pioneer) and Suisei (Comet), between them will study the solar wind and examine the hydrogen cloud surrounding the comet. The Soviet Union's Vega 1 and Vega 2 will analyze the abundant dust motes and charged gases that envelop the comet's nucleus. Most remarkable of all, data and pictures from the Vega twins will enable European scientists to chart Halley's course precisely enough to allow their probe, Giotto...
...opted in 1981 against launching a Halley's probe of its own, NASA nonetheless remains smack in the middle of the action. The agency plans to dedicate part of two shuttle missions, including the flight that will boost aloft Teacher Sharon Christa McAuliffe, to comet- related experiments. The Solar Max satellite, brought back to life l8 months ago by a shuttle repair crew and now performing its normal duty of monitoring the sun, will examine Halley's off and on for about 60 days. Pioneer 12, in orbit around Venus, will watch Halley's when it ducks behind...
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...
...astronomer, proffered a detailed model for the anatomy of a comet. In a delightfully evocative phrase, Whipple declared that comets are "dirty snowballs," dark conglomerates of mostly frozen water stippled with rocky fragments, dust particles and trace elements. As one of these snowballs swoops toward the sun, said Whipple, solar radiation begins to vaporize ice and frozen gases on the comet's sunward surface by a process called sublimation. The gases, carrying dust with them, form a light-reflecting coma that makes the comet visible from earth...
...snowballs, Dutch Astronomer Jan Oort conceived of a kind of enormous warehouse for comets, which would come to be known as the Oort Cloud. Basing his calculations on the shape of cometary orbits and the number of new comets observed each year, Oort postulated that the cloud surrounds the solar system in a vast region 30,000 to 100,000 astronomical units from the sun (one AU is about 93 million miles, the distance between earth...