OUR SOLAR FAMILY 



13 



the largest of the planets (317 times as heavy as the earth) 

 takes its name from the king of the Roman gods. Mars 

 shines with a reddish brown color, and on this account 

 bears the name of the Roman god of war. Saturn is plainly 

 visible at times, but the bright concentric rings, composed 

 of little moonlike bodies that surround it and revolve about 

 it, can be seen only 

 with a telescope. 

 When once in about 

 every fifteen years 

 Saturn is so situated 

 that we have a view 

 of the broad side of 

 these rings, the tele- 

 scope reveals what 

 is probably the most 

 beautiful sight in 

 the solar system. 

 Mercury is so close 

 to the sun that it 

 can be seen by the 

 naked eye very 

 rarely; Uranus can 

 be singled out only 

 by very sharp eyes; and Neptune is so far away that it 

 cannot possibly be seen without the aid of a telescope. 



The planets have no light of their own, as do the true 

 stars, but the light which comes to us from them is a re- 

 flection of the light of the sun. When the astronomer turns 

 his telescope on Neptune and .its moons, he sees it by rays 

 of light which, in making the trip from the sun to Neptune 

 and, by reflection, back to the earth, have traveled five 



MARS 



Most like the earth of all the planets. It is 

 supposed to have a polar ice cap. The noted 

 astronomer Lowell argues that Mars may 

 be inhabited. 



