386 ] Our Earth and Its Fellow Planets 



There is, indeed. Stars are blazing masses of glowing gas, like 

 our sun. We are told that something like two or three billion 

 years ago a great piece of our sun was drawn away from the main 

 body and separated into nine parts. The generally held theory is 

 that the gravitational attraction of a passing star pulled away a 

 portion of the sun's mass, which later broke up into separate drops. 

 Some of these went much further away from the sun than others, 

 but all cooled into solid balls, and all controlled by the sun's pull 

 or force of gravitation proceeded to revolve about the sun. These 

 are the planets. 



From planet Earth we can see five of the others Mercury, Mars 

 Venus, Saturn, and Jupiter without using a telescope. The re- 

 maining three Uranus, Neptune, and Pluto are too faint to be 

 seen with the naked eye. 



How PLANETS DIFFER FROM STARS 



It will help you to distinguish planets from stars if you 

 keep several points in mind. Planets shine steadily they do not 

 twinkle as stars always appear to do. This difference comes about 

 because the beam of light that radiates from a planet is wider than 

 that from a more distant star, and is therefore less influenced by 

 our atmosphere. Also, the way the planets move about the sky is 

 different from the movement of the innumerable stars that sur- 

 round them. 



Like stars, the planets appear first in the east and seem to travel 

 westward; but you will notice that the position of the stars with 

 relation to one another remains constant. The position of the 

 planets among the stars, however, is variable. 



If you start to keep track of a planet, you will see it change its 

 heavenly neighbors week after week. More than two thousand 

 years ago, the Greeks noticed these "stars" that behaved differently 

 from the rest, and named them planets -in Greek this means 

 "wanderers." 



How TO LOCATE THE PLANETS 



The night sky may well bewilder parent and child as they 

 first try to distinguish planets from stars, and one star group from 



