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“The height of the Chacoan culture lasted from A.D. 1055 to 1083, corresponding to the period of most intense building activity. This period also produced the most startling series of events in the heavens that have taken place within the Iast few thousand years. In July 1054 the supernova which produced the Crab Nebula blazed in the daytime skies for three weeks and remained visible at night for nearly two years. Some twelve years later, in 1066, Halley's Comet appeared, frightening Europeans on the eve of the Battle of Hastings. Another decade later, on March 7, 1076, a total solar eclipse was visible south of Chaco Canyon. In 1077 sunspots large enough to be seen with the naked eye were reported in China, beginning a more than two-hundred-year period of unusual sunspot activity. And again on July 11, 1097, another total eclipse passed over the Southwest. The inhabitants of Chaco Canyon may have been so startled and puzzled by these events that they became devoted sky watchers, investing much more effort in astronomy than they might have had the heavens been ordinary and unchanging.”