The Starry Heavens 175 



the sun each year reaches that distance either side of 

 the celestial equator. It is farthest north in June and 

 farthest south in December. Since the sun is always 

 on the ecliptic, astronomers find the position of the 

 ecliptic in the heavens by observing the sun throughout 

 the year. 



The zodiac. The moon in its motion around the earth 

 never gets very far from the ecliptic. The planets, too, 

 keep near the ecliptic. Within a belt only 1 6 degrees wide 

 that is, 8 degrees on each side of the ecliptic the moon 

 and all the major planets may always be found. This 

 fact was noticed by those who observed the heavens in 

 ancient times, and they called the belt the zodiac, or 

 zone of aninials. They fancied they could see among 

 the stars along this belt the outlines of various animals. 



The constellations. The peoples of ancient times 

 mapped out the heavens into divisions, which are called 

 constellations. A few constellations have been added 

 in modern times. The imaginary boundaries of a con- 

 stellation extend far enough to meet those of surround- 

 ing constellations, so that the entire celestial sphere 

 is covered with constellations and every star is assigned 

 to some constellation or other. Many constellations 

 include a prominent group of stars which the ancients 

 supposed to form some object or the figure of an animal 

 or man, and which gave to the constellation as a whole 

 its name. 



If you were to map out the celestial sphere into a num- 

 ber of areas, each of which included one group of stars, 

 your -map would probably be as good as those which 

 we use. The names you would apply to the figures 



