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National Geographic : 1925 Jan
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INTERVIEWING THE STARS Photograph from Mt. Wilson Observatory A DARK NEBULA IN AQUILA The spiral nebulae have been found to be traveling away from or toward us at the rate of 500 to 6oo miles per second. Light that comes into the telescope from them to-day brings us records of what was happening in them when dinosaurs were roaming the earth. Thus does the Past live in the Present and project itself into the Future in the field of astronomy. So that every bright star exudes oceans of cosmic dust particles and inconceiv able numbers of free electrons, which, pursued through space with the whiplash of driving light, must move on and on, forever seeking company and finding it. CELESTIAL CLOUDS WITH "SILVER LININGS" Finally great clouds of this cosmic dust form. If these vast clouds occur in regions remote from stars they are dark and forbidding, the "coalsacks" of the heavens; but if they chance to form in regions peopled by stars, they become cosmic clouds with "silver linings." In some cases the spectroscope reports that the light is merely reflected star light, while in other cases the star light clearly arouses within the dust a glow of its own. "Star dust" has long been a figure of speech, but now it has come to have a literal as well as a figurative meaning. Nordmann, the eminent French as- tronomer, offers the climax to the story. These huge, shapeless nebula form "the breeding ground where stars are born." The theory generally held as to how stars come into being is that the accumu lating clouds of cosmic dust become so heavy that gravitation begins to draw to gether the particles that constitute them. As the process goes on, the flying mole cules begin to collide with one another. These collisions stir the electrons in their atomic orbits, and heat is generated, with the result that the mass begins to glow now red, now yellow, now white, and now blue-as contraction goes on and tem perature rises. It has now reached the limit of contrac tion, and we have a star of the Rigel type, 13,000 times as bright as our sun. The star is in its prime. The vast pressures and terrific temperatures resolve all mat ter to its simplest form. No complex atom like that of iron could hold together amid such frenzied surroundings any 119
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