National Geographic : 1952 Feb
246 National Geographic Photographer J. Baylor Roberts Another Square of the Heavens Is Charted at Palomar Mountain, California After a night of exploring space, astronomer Albert G. Wilson marks off as "captured" a section of the sky as large as the Big Dipper's bowl. Dark squares on his chart show that the Big Schmidt telescope (page 248) has made nearly half the 1,870 photographs needed to complete the National Geographic Society-Palomar Observatory Sky Atlas. This map, itemizing the heavens, will give a new picture of the universe (page 245). omers deduced that the Milky Way, which we see as a band of light across the heavens, is really a great aggregation of stars, flat and round and slowly rotating. Our sun, they found, is only one of perhaps 200 billion stars that make up this star wheel, or galaxy. Hundreds of Millions of Nebulae Finally, as telescopes became even more powerful, it was discovered that this Milky Way Galaxy is but one of hundreds of mil lions of similar aggregations of stars, dust, and gas scattered at tremendous distances all through the space around us. We call them nebulae, or galaxies. To measure this vastness, the astronomers invented a measuring rod known as the "light year," the distance which light, speeding 186,000 miles a second, travels in one year about six million million miles.* The 200-inch telescope, penetrating three times as far as the Schmidt, has photographed nebulae a billion light-years away. Light from these far-off objects has been on the way to the earth for a billion years. It started far back in the Pre-Cambrian Age, when life on earth, if any, was at a primitive stage. All of man's recorded history is a mere tick of the clock compared with the time that this light has been speeding on toward our telescopes. We see these bodies as they were ten million centuries ago. Today they may be entirely different, perhaps have re ceded far beyond the range of the "Big Eye," or may no longer exist at all. Astronomical Artillery in Action Night after night, for two years, the Schmidt camera has been constantly at work. Like a mighty cannon, which it resembles, the instrument is trained systematically on target after target, each a designated section of the night sky, and "fired" with exposures * See "News of the Universe," by F. Barrows Col ton, NATIONAL GEOGRAPHIC MAGAZINE, July, 1939.