Читать книгу Star-land: Being Talks With Young People About the Wonders of the Heavens онлайн

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I have shown you that the sun is intensely hot, and a very long way off, and enormously big. And now we have to describe the appearance of the surface of the sun when we examine it closely.

Fig.12.—Looking at the Sun.

If you get a piece of very dark glass, or if you smoke a piece of glass over a candle, then you can look directly at the sun with comfort. A nicer plan is to prick a pinhole in a card, through which you can look at the sun without any inconvenience. Generally speaking, a view of the sun in this way will show you only a uniformly bright surface. To study the face of our great luminary carefully, you must use the aid which the telescope gives to the astronomer. A very good way of doing this is shown in Fig.12. A small telescope, fixed on a stand, is pointed to the sun, and, the eyepiece being drawn out somewhat further than when direct observations are being made, the sun draws its own picture on a screen. This may be examined without any inconvenience, or without the necessity for any protection to the eye, and a number of young astronomers can all view the sun at the same moment. On such a picture you will generally see the brilliant surface marked with dark spots, which are sometimes as numerous as in the case represented in Fig.13. These spots present very different appearances according to circumstances. One such spot when seen with a very powerful telescope showed the wonderful structure which is represented in Fig.14.