Our Earth and Its Fellow Planets [ 399 



However, Pluto was not discovered until twenty-five years after 

 his death! 



The Mysterious Minor Planets 



With a telescope you may make the acquaintance of another 

 group of heavenly bodies that are not stars for they are within 

 our solar system and yet lack the full status of planets. These are 

 the asteroids (from the Greek word aster, meaning "star") . They 

 are found in the great gulf of space between the orbits of Mars 

 and Jupiter. 



Even through the telescope the asteroids show up only as points 

 of light (like the stars), though they have the solid mass of planets. 

 This is explained by the far smaller size of the asteroids as com- 

 pared to the full planets; the largest asteroid is less than five 

 hundred miles across and the smallest, only five or ten miles. 



SOLVING THE PUZZLE OF THE MINOR PLANETS 

 The answer to the puzzle of why several thousand of these 

 minor planets (or asteroids) exist in an area where one single 

 planet might be expected, may lie in the theory that once a single 

 planet did move along this path. This unknown planet may have 

 broken into the thousands of fragments that now continue to move 

 in the same path. Meteorites that strike our earth are also believed 

 to be the remains of this vanished planet. 



The MoonOur Neighbor in Space 



To young children, the moon is probably the most interesting 

 object in the sky. It is by far the brightest of the night sky; and 

 though the sun is overwhelmingly brighter, it does not have the 

 moon's rather mysterious appeal. The moon's gradual disappear- 

 ance and equally gradual return to view each month may seem very 

 odd, to say the least, until a child understands the cause. 



A child may take in all seriousness talk about "the man in the 

 moon," and by the time he realizes that this is merely an imagina- 

 tive phrase, he may have begun to wonder about such terms as 

 the "craters" and the dark plains (often called seas or "maria") 



