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Space Topics: Planetary AnalogsStars Above, Earth BelowAstronomy and Space Exploration in America's National ParksChaco Culture National Historic Park, New Mexicoby Tyler
Nordgren Astronomy National ParkAs I write this, I am looking out into a beautiful winter snow. Waves of cloud blow up and over Fajada Butte, obscuring it in a brief flurry of falling snow, and then passing on to reveal the towering yellow rock face against a colorless sky. It’s spellbinding, even for an astronomer that came to this quiet out-of-the-way park in order to help observe sunrise markers predicting, and then eventually announcing, the arrival of the winter solstice. Today I have been here a full week and have only seen the Sun rise once. What is normally one of the best months for clear skies, has instead produced a weather forecast of clouds and snow for as far as the predictions extend.
I, like many people, first heard of Chaco Canyon from Carl Sagan’s Cosmos. In the third episode of the TV show, we saw Carl walking around the Great Houses of Chaco discussing just a few of the amazing alignments of architecture, which -- when combined with a summer solstice Sun -- produce a play of light on niches and petroglyphs that fire the imagination. Indeed, what we saw in Cosmos was only a very tiny example of the number of ways in which what the Chacoans left reveal their awareness of the Sun, its changing pattern of equinoxes and solstices, and the motion of the Moon and its subtle 18.6-year cycle of full Moon major and minor rise and set locations on the horizon. Everything in this canyon seems to speak of an awareness of astronomy. Are all of these alignments intentional? Probably not. With enough walls, windows, petroglyphs, and Great Houses, I could probably find an alignment that foretells my birthday by the rising of a Sun a thousand years before I was born. However, the Hopi, Zuni, and other modern puebloans, who are descendents of the Chacoans that constructed these monuments between 850 and 1150 AD, still have traditions of observing the Sun and Moon for calendrical and ceremonial purposes.
Standing in the midst of a still imposing thousand year old ruin that stretches over three acres, I can easily see the connection between these ancient sky watchers and our culture that is forever inserting leap-seconds and recognizing leap-years in order to keep our modern clocks and calendars in synch with the motion of the Earth around the Sun. And let us not forget that even many of our religious celebrations still depend on the travel of the Sun and Moon; to name just one, Easter is still the first Sunday after the first full Moon after the spring equinox. In addition, to the Sun and Moon, the evidence is intriguing that the Chacoans recorded other astronomical events. During a single 43 year period during the height of the Chacoan culture in the canyon, there was the supernova of July 1054 that was visible during the day for weeks, the apparition of Halley’s Comet in 1066, and solar eclipses passed over the region in 1076 and again in 1097. These are still some of the most spectacular sights a person can see in the sky with the naked-eye. There is no one alive today, and has not been since the time of Tycho and Kepler, who could claim to have seen all of these phenomena in one lifetime. Yet it all happened here to a people that give every evidence of closely observing the sky. Three panels of rock art may record these events within the park. To the west, a shadowed section of sandstone may contain the observational record of the Crab supernova, while on the wall beneath, not as well protected from the elements a faded spiral with flames of red trailing downward may be a representation of Halley’s Comet. Lastly, on a rock face to the east, nestled in between petroglyphs of Kokopelli and far more modern visitors to the park, there is a circular disk pecked into the stone with curling tails billowing out in all directions accompanied by a smaller pecked spot to the lower right. Given the impressive nature of a total solar eclipse, it does not strain credulity to speculate that this is a record of one of the eclipses, with its attendant coronae and even the presence of Venus which would have been in just the right position to have been seen.
Add to all of this amazingly dark skies, an observatory beside the visitor center, and a vigorous astronomical program for the public during the months without snow, and this is the park for anyone who has ever looked at the sky. I am here until the winter solstice, and I have no idea when I will see the stars, Sun or Moon again. |
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