Jimmy Westlake: Viewing the Southern Cross
April 11, 2016
Though the Southern Cross is the tiniest of our 88 official constellations, its reputation is far larger than its actual size, even though most people living in the Northern Hemisphere have never seen it. The flags of Brazil, New Zealand and Australia all bear an image of the stars of the Southern Cross.
The Southern Cross, or Crux, as it is officially named, used to be visible from much of Europe, but not anymore. It was originally seen by the ancient Greek civilization about 1000 B.C. and was then considered to represent the hind feet of a giant Centaur pictured in the stars.
Across the centuries, however, the slow wobble of Earth on its axis — called precession — carried the stars of Crux southward and out of view of Greece and the rest of Europe. It was gradually forgotten by the Europeans.
European sailors rediscovered these stars during the 16th and 17th centuries, as they began sailing the southern seas. Many of these explorers were of the Christian faith and were awestruck by the resemblance of these stars to a tiny crucifix in the heavens.
Amerigo Vespucci, the man for whom the Americas are named, claimed to be the first European to ever see these stars during his third voyage in 1501. That might be true, but the four stars forming the Southern Cross didn't appear on star charts as separate and distinct from the Greek Centaurus constellation until Dutch astronomer Petrus Plancius depicted Crux on his celestial globe in 1589. It officially became the smallest of our 88 constellations in 1920.
Crux is not visible in its entirety from any location more than 27 degrees north of the equator, which includes most of the United States. April and May are the best months to observe it.
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I've seen just the top star of the Southern Cross, ruddy Gacrux, briefly show itself above the southern horizon from New Orleans, Louisiana and witnessed the entire cross barely clear the ocean waves from Key West, Florida. It wasn't until I traveled to the big island of Hawaii that I could see the Southern Cross standing well above the southern horizon in all of its glory.
Eventually, Earth's precession will carry Crux back into the view of mid-northern latitudes once again, but that will be centuries in the future. Until that happens, traveling to the tropics is the only way to view the Southern Cross for yourself.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Jimmy's astrophotography website at http://www.jwestlake.com.
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