Our Earth and Its Fellow Planets 



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What Telescopes Tell Us: Powerful modern telescopes reach out 

 across hundreds of millions of light-years to penetrate some of 

 these distant galaxies. (A light-year represents the distance that 

 can be covered by light in a year's time: 6,000,000,000,000 miles!) 

 But even the comparatively "close" stars of our own universe are 

 so far away that they appear as mere points of light. Our most 

 powerful telescopes make these stars appear brighter, but with no 

 more defined form than when we observed them with the naked 

 eye. 



MARS 

 MOON 

 EARTH 

 VENUS 

 MERCURY 



JUPITER 



URANUS 



NEPTUNE 

 SATURN PLUTO 



(Courtesy A.M.N.H.) 

 OUR PLANET NEIGHBORS VARY GREATLY IN SIZE 



The earth is neither the largest nor the smallest of the planets. From Jupiter, 

 the largest, with a diameter of eighty-seven thousand miles, to Mercury with a 

 diameter of only three thousand miles, there are remarkable differences among 

 the members of the sun's family. However, all move around the sun in the same 

 direction. A year on any planet is the time it takes that planet to make a complete 

 revolution around the sun. The planets are dwarfs, compared to the sun, with its 

 864,000-mile diameter. The sun, a ball of flaming gas, is not a planet but a star. 



On the other hand, when we look at any of the planets (except 

 Pluto, the most distant one) through a large telescope, they appear 

 as round disks, similar to our moon. Jupiter, largest of the planets, 

 which is hundreds of millions of miles distant from the earth, 

 needs to be magnified only fifty times to appear as large as the 

 moon. 



