The Chaco Culture National Historical Park is an International Dark Sky Park with much to offer amateur astronomers. Located in the remote northwest of New Mexico, it is accessible only by dirt roads. Skies are dark, with spectacular desert scenery, and the great house showpieces of the “national mall” of the Chaco civilization. The great houses were built to host large ceremonies and included many features for astronomical observations.

Fajada Butte near the park entrance is the location of the Sun Dagger solstice marker (no longer accessible)

Chacoan civilization was at its height in an 11th century, filled with spectacular astronomical events visible from the canyon. These included two super novas (1006 and 1054) visible during the day, a total solar eclipse on July 11, 1097, and the benchmark 1066 appearance of Haley’s Comet. Chaco Canyon’s large collection of petroglyphs and pictographs include likely astro images of these spectacular events. The whole world shares the same sky, a place like Chaco allows us to share images from the skies seen by our ancestors.

Two remarkable pictographs are located along the trail from Chaco Wash to the Peñasco Blanco great house. The Super Nova pictograph is well preserved on a shaded horizontal rock face 16' above the trail. Adjacent to it on a vertical rock face is a barely visible pictograph that has been proposed as a representation of Haley’s Comet or the Sun during an eclipse. This pictograph is so faded that some visitors miss it all together. It is difficult to photograph. The image above has enhanced the saturation of the pictograph's colors colors of the pictograph to give us our best look at this image in hundreds of years.

The Super Nova Pictograph is often associated with SN1054, the parent super nova of the Crab Nebula. This event is spanned by construction of the Peñasco Blanco great house, directly above the pictograph near the canyon rim, from 900 to 1125 CE. The orientation of the star to the right of the crescent (with artist head in, on his back) corresponds to the pre-dawn appearance of the super nova and the moon on July 5, 1054, directly across the canyon. SN1054 was discovered the day before by Chinese observers and would have been near its peak brightness.

Other possible subjects for this image include the Moon and Venus as well as the even brighter super nova of 1006. Although brighter, SN1006 was very low on the southern horizon on this latitude and not easily visible from this location on the southwest wall of the canyon.

Below the possible super nova is a very faded pictograph in red and yellow. The concentric circles suggest representations of the sun. The feathered or flaming looking tail to the side has been suggested as a coronal mass ejection during the total solar eclipse of July 11, 1097. Visible from Chaco, near the peak of a solar cycle, a CME may have given the corona an asymmetric appearance during totality. Looking at the enhanced image above, the appearance closely resembles a comet's tail. The spectacular 1066 appearance of Haley's comet, was only 12 years after SN1054. The proximity of the two images, leads me to favor the Haley's comet interpretation.

More precise dating could narrow down possible interpretations. Dating of pictographs is possible, but requires removal of part of the image. More precise dating evidence can eliminate possibilities, but not prove a specific interpretation. The subjects of these pictographs will probably never be known with certainty. The contextual dates, location, and the orientation of image provide compelling evidence for the SN1054 interpretation. The adjacent pictograph looks very comet like to the modern eye and the proximity of dates makes the 1066 Haley's appearance plausible.

from the Peñasco Blanco Trail from the Backcountry Trail Guide, Chaco Culture NHP, Western National Parks Assn. available at the park bookstore.

Reaching Chaco Canyon National Historical Park in north-west New Mexico requires travel over erratically maintained dirt roads and a low water crossing across the Escavada Wash. The location is dry high desert with temperatures ranging from hot in the summer to below freezing in the winter. Flash floods are a concern particularly during the monsoon and it snows in the winter. Camping with potable water is available by reservation for visitors to the park, but food other than a few snacks is not.

Once in the canyon, reaching the pictograph site requires a 6 mile round trip on relatively flat foot trails from the Peñasco Blanco trail head, off the park's loop road. Altitude, very low humidity and temperatures from freezing to 100F in summer can make the hike a challenge. When water is running in Chaco Wash it is often impassible. On our trip, we found Chaco Wash an 8’ wide, and 6’ deep muddy ditch, with about a foot of water running in it. Steep slippery sides with "quicksand" and about a foot of water made crossing the wash a real adventure.

Milky Way setting over Pueblo Bonito. The loop road 9 PM closing time allowed just enough time in October for this image.

Chaco Canyon has star gazing and astrophotography opportunities worthy of its status as an IDA International Dark Sky Park. The image below of Fajada Butte (site of the Sun Dagger) with an earthshine crescent moon, was taken before my hike out the Super Nova Pictograph.

For more information on Chaco Culture National Historical Park see: https://www.nps.gov/chcu/index.htm