THE EARTH AND ITS NEIGHBORS 



411 



are so far from the sun that they do not receive much 

 heat and light. 



The time it takes for these planets to go once around the 

 sun is given in the following table with the distance of 

 each from the sun. The time is represented in number of 

 earth's days and years. 



Planets Time for one revolution Distance from the sun 

 Mercury 88 days 36 million miles 



Venus 



Earth 



Mars 



Jupiter 



Saturn . . 



225 days 67^ 



36sidays 92 



687 days. . w 



u| years 



29! years 886 



Uranus 84 years 1780 



Neptune 165 years. 2790 



These planets with the sun compose the solar system. 

 The entire solar system is moving through space and is one 

 system among hundreds of others. The distant stars 

 are suns much larger than our sun, and each one is at the 

 center of a system of its own. The earth itself is but a 

 small particle of matter when compared with all the 

 matter in the universe. 



Mercury and Venus do not have moons or satellites. 

 The earth has one, Mars has two, Jupiter has five, Saturn 

 has nine, Uranus has four, and Neptune has one satellite. 

 These moons move around the planets in much the same 

 way as the planets move around the sun. The moons are 

 not self-luminous, but only reflect the light received from 

 the sun the same as objects on the earth reflect light to 

 our eyes. 



286. The Stars. The stars other than the planets 

 are at a very great distance from us, so far that telescopes 

 do not make them look much larger than they do to the 

 unaided eye. When the planets are viewed with a good 



