CHAPTER TWELVE 



THE PLANETS 



PLANETS are very much nearer to us than the stars, 

 for which reason more is known about them. Viewed 

 with a telescope, a planet shows a disk instead of a mere 

 point of light. With the naked eye it may often be 

 distinguished from a star by its steady light. It does 

 not twinkle like the stars except when near the horizon. 

 All the planets are confined to the belt of the heavens 

 traversed by the sun. You will never see any of them 

 in the northern sky or much lower in the south than 

 you see the sun in winter, for they revolve around the 

 sun in orbits that lie nearly in the ecliptic or plane of 

 the orbit of the earth. The most important observa- 

 tion you can make regarding the planets is that they 

 change their apparent position among the stars from 

 week to week, whereas the real stars keep their same 

 position so far as you can see. The moon and sun were 

 classified as planets in ancient times because they, too, 

 move among the stars. 



Size and motion of the planets. In the order of their 

 distance from the sun, the eight major planets are : 

 Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, 

 and Neptune. Of the first four, the earth is the largest, 

 but each of the second four is very much larger than 

 the earth. Jupiter, the largest, is about 1300 times 

 the size of our globe. 



Mercury moves about the sun in an ellipse much 

 smaller than the orbit of the earth and requires but 

 88 days to complete a revolution. In other words, 

 its year is less than one fourth of ours. Neptune, which 



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