THE EARTH'S PLACE IN THE UNIVERSE 15 



hemisphere; but because of dust and vapor in the atmos- 

 phere, the number of these stars that can readily be seen is 

 reduced to about 2,500. The use of an opera glass or a 

 small telescope reveals many which cannot be seen by the 

 naked eye. In the whole sky, with the largest telescope, 

 100,000,000 may be seen. The stars look like bright points 

 and twinkle most perceptibly when they are near the 

 horizon, which is the circle where earth and sky seem to 

 meet. 



3. Constellations. Certain groups of bright stars near 

 together are known as constellations. The people of ancient 

 times gave names to these groups, sometimes in memory of 



FIG. 1. SCORPIO 



The constellation Scorpio may be seen in the southern part of the sky 

 during the summer. At 9 p. m. at the middle of July, the brightest star, 

 Antares, is directly over the southern point of the horizon. 



a hero or of an event. The brighter stars in a constellation 

 outline an object or designate the position of some important 

 part of the body of a man or animal. Aldebaran is a star 

 in the eye of Taurus, the bull, and the cluster called the 

 Pleiades is in his shoulder. 



Orion is farther south than Taurus and rises a little later. 

 He is a hunter who has his club raised to strike the bull. 



