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THE FIXED STARS

rapidly it cools off, just as a cup of water cools off faster than a pot full.

The revelations of the spectroscope makes it very probable that every star has a life history. It began as a nebula, which, in the course of ages, slowly condensed into an intensely hot, blue-coloured star. The condensation going on, the star becomes yet hotter, until it reaches its highest temperature. Then, cooling off, its colour changes to white, yellow, and red, and the lines in its spectrum become darker and more numerous. Finally, its light dies away, as a fire flickers out when the supply of fuel is exhausted, and the star becomes a dark opaque body,—its life has ended. The greater the mass of the star the longer its life. Thus it is that the stars we observe seem to be of all ages, from the infantile nebula to the star dying of old age.

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