iamencyclopedia

  ASTRONOMY                Astronomy is  the study of all extraterrestrial objects and phenomena. Until the invention of the  telescope  and the discovery of the  laws of motion  and  gravity  in the 17th century, astronomy was primarily concerned with noting and predicting the positions of the  Sun ,  Moon , and  planets , originally   astrological  purposes and later for  navigational  uses and scientific interest. The catalog of objects now studied is much broader and includes, in order of increasing distance, the  solar system , the  stars  that make up the  Milky Way Galaxy , and other, more distant  galaxies . With the advent of scientific space probes,  Earth  also has come to be studied as one of the planets, though its more-detailed investigation remains the domain of the  Earth sciences . NASA defines astronomy as simple "the study of stars, planets and space."                                           Astronomy is split into  observational  and  theoretica