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Science2 - 00034

Science2 - 00034 - Untitled sun in the comet that visits us...

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Untitled sun, in the comet that visits us once in a thousand years, in the star whose distance is incalculable, and in the great clouds of "fire-mist" that we call nebulæ. In considering the evolution of the stars let us keep two points clearly in mind. The starting-point, the nebula, is no figment of the scientific imagination. Hundreds of thousands of nebulæ, besides even vaster irregular stretches of nebulous matter, exist in the heavens. But the stages of the evolution of this stuff into stars are very largely a matter of speculation. Possibly there is more than one line of evolution, and the various theories may be reconciled. And this applies also to the theories of the various stages through which the stars themselves pass on their way to extinction. The light of about a quarter of a million stars has been analysed in the spectroscope, and it is found that they fall into about a dozen classes which generally correspond to stages in their evolution (Fig. 21).
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