Sky Study 905 



THE SUN 

 Teacher's Story 



To be retold to pupils. 



If, only once in a century, there came to us from our great sun, light and 

 heat, bringing the power to awaken dormant life, to lift the plant from the 

 seed and clothe the earth with verdure, then it would indeed be a miracle. 

 But the sun by shining every day cheapens its miracles in the eyes of the 

 thoughtless. While it hardly comes within the province of the nature- 

 study teacher to make a careful study of the sun, yet she may surely stimu- 

 late in her pupils a desire to know something of this great luminous center 

 of our system. 



Our sun is a great shining globe about one hundred and ten times as 

 thick through as the earth, and more than a million times as large. If we 

 look at the sun in a clear sky, it is so brilliant that it hurts our eyes. Thus, 

 it is better to look at it through a smoked glass, or when the atmosphere is 

 very hazy. If we should see the sun through a telescope, we should find 

 that its surface is not one great glare of light but is mottled, looking like a 

 plate of rice soup, and at times there are dark spots to be seen upon its sur- 

 face. Some of these spots are so large that during very "smoky weather" 

 we can see them with the naked eye. In September, 1908, a sun-spot was 

 plainly visible ; it was ten thousand miles across, and our whole world could 

 have been dropped into it with a thousand miles to spare all around it. We 

 do not, know the cause of these sun-spots, but we know they appear in 

 greater numbers in certain regions of the sun, above and below the equator. 

 And since each sun-spot retains its place on the surface of the sun, just as a 

 hole dug in the surface of our earth would retain its place, we have been able 

 to tell by the apparent movement of these spots how rapidly and in which 

 direction the sun is turning on its axis; it revolves once in about twenty-six 

 days and, since the sun is so much larger than our earth, a spot on the 

 equator travels at a rate of more than a mile a second. There is a queer 

 thing about the outside surface of the sun — the equator rotates more 

 rapidly than the parts lying nearer the poles ; this shows that the sun is a 

 gaseous or liquid body, for if it were solid, like our earth, all its parts would 

 have to rotate at the same rate. At periods of eleven years the greatest 

 number of spots appear upon the sun. 



Another interesting feature of the sun is the tremendous explosion of 

 hydrogen gas mixed with the vapors of calcium and magnesium, which 

 shoot out flames from twenty-five thousand to three hundred thousand 

 miles high, at a rate of speed two hundred times as swift as a rifle bullet 

 travels.! Think what fireworks one might see from the sun's surface all the 

 time ! One would not need to wait until the Fourth of July for fireworks 

 there. These great, explosive flames can be seen by the telescope when the 

 moon eclipses the sun, and they have been analyzed by means of the 

 spectroscope. Besides these magnificent explosions, there is surrounding 

 the sun a glow which is brighter near the sun'sl surface and paler at the 

 edges ; it is a magnificent solar halo, some of its streamers being millions of 

 miles long. This halo is called the Corona, and is visible during total 

 eclipses. By means of the spectroscope we know that there are about forty 

 chemical elements in the sun, which are the same as those we find upon our 

 earth. 



As the sun weighs 330,000 times as much as the earth, the force of 

 gravity upon its surface is twenty-seven and two-thirds times as much as it 



