UntitledThis spiral nebula is seen full on. Notice the central nucleus and thetwo spiral arms emerging from its opposite directions. Is matter flowingout of the nucleus into the arms or along the arms into the nucleus? Ineither case we should get two streams in opposite directions within thenucleus.]THE BIRTH AND DEATH OF STARS§ 3Variable, New, and Dark Stars: Dying SunsMany astronomers believe that in "variable stars" we have another star,following that of the dullest red star, in the dying of suns. The lightof these stars varies periodically in so many days, weeks, or years. Itis interesting to speculate that they are slowly dying suns, in whichthe molten interior periodically bursts through the shell of thickvapours that is gathering round them. What we saw about our sun seems topoint to some such stage in the future. That is, however, not thereceived opinion about variable stars. It may be that they are starswhich periodically pass through a great swarm of meteors or a region of
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