Rock art records an ancient blast

Astronomers believe they've found the first North American record of the a.d. 1006 supernova.
By | Published: June 5, 2006
SN 1006 petroglyph
This rock carving may celebrate the appearance of a supernova seen in 1006. The star is the large rayed circle right of center. Above and to the left is a scorpion, possibly representing the constellation Scorpius.
John Barentine, Apache Point Observatory
June 5, 2006; updated June 7
One millennium ago, the brightest star in recorded history appeared briefly in the southern sky. Chroniclers in Asia, the Middle East, and Europe marveled at the sight and tried to glean its astrological meaning. Modern astronomers identify the event as a supernova, the explosive death of a star some 7,100 light-years away. With an estimated magnitude of –7.5 at its brightest, the supernova rivaled the glow from a quarter Moon.
SN 1006 sky
Astronomers simulated the southern sky as it appeared midnight, May 1, 1006, from the location of the petroglyph. The supernova grazes the local horizon near center. The constellation Scorpius curves upward at left.
Gilbert A. Esquerdo, Planetary Science Institute, Tucson, and SAO
Now, John Barentine of New Mexico’s Apache Point Observatory and Gilbert Esquerdo of Tucson’s Planetary Science Institute think they’ve found a rock carving, or petroglyph, that depicts this striking astronomical event. “The supernova of 1006 was perhaps the brightest such event visible from Earth for thousands of years, yet, to date, no representations of the event have been identified in Native American art,” notes Barentine. If confirmed, the finding would support the idea that ancient Native Americans commemorated celestial changes in their cultural record.

The petroglyph is located in Arizona’s White Tanks Regional Park, near Phoenix. The Hohokam people occupied the region from about a.d. 500–1100. The carving shows a large rayed circle beneath a scorpion symbol. The 1006 supernova was visible in the constellation Lupus, southwest of Scorpius the Scorpion. “Without my background in astronomy, I probably wouldn’t have recognized the petroglyph for what it might represent,” Barentine says. The astronomers presented their findings today at the American Astronomical Society meeting in Calgary, Canada.

Petroglyphs, which are formed by hammering away a rock’s surface, are among the most durable art forms. “Standing in the desert heat after studying the petroglyphs, the span of the ages hit home,” Esquerdo muses. “It was the change in the sky that had brought that artist, as well as us, to that spot 1,000 years apart.”

Chemical dating, which relies on the abundance of certain elements in the rock varnish, could narrow down the petroglyph’s age. If studies confirm the carving dates from the early 11th century, the scientists say it would attest to a connection with the supernova. Knowing exactly when one piece of rock art was created would benefit archaeologists. Barentine explains: “Quantitative methods such as carbon-14 dating … lack precision of more than a few decades, so any depiction in art that can be fixed to a specific year is extremely valuable.”

However, archaeologists and astronomers specializing in how ancient peoples saw the sky say a link between the carving and the 1006 supernova is circumstantial, at best. “There are many images out there that could be interpreted as star bursts or suns or planets, so you have to be very cautious,” Todd Bostwick, a Phoenix archaeologist and an expert on Hohokam culture, told the Associated Press.

Other Southwest petroglyphs have been associated with historic astronomical events. The best known is a star-and-crescent symbol painted on rock in Chaco Canyon National Monument, New Mexico. Astronomers once suggested the art depicts a July morning when the crescent Moon was near the supernova of 1054, which formed the Crab Nebula. However, this interpretation is no longer widely accepted.