January 16, 2014 | 5
Thousands of years ago a star exploded in a supernova, leaving behind the glorious riot of colored gas we see now as the Crab Nebula. The light from this explosion reached Earth in 1054 A.D., creating what looked like a new bright star in the sky as recorded by ancient Chinese and Arab astronomers. Native American cave paintings, too, have been thought to represent the supernova, but when one scientist went to look at the paintings in person recently he arrived at a different story altogether.
Back in the 11th century, the supernova would have been hard to miss. Chinese records suggest it was brighter than all the stars and planets, surpassed in luminosity only by the sun and the moon, and took two years to fade from sight. Because it was so striking, experts have assumed many people would have created homages to the sight. Rock art in the American Southwest, for instance, has been linked for the past 50 years to the Crab supernova.
The idea started in 1955 with Palomar Observatory photographer William C. Miller, who published images of two cave paintings in northern Arizona—one in White Mesa and another in Navaho Canyon—featuring what looks like a crescent moon and a star. The sites show evidence that they were inhabited in 1054, Miller pointed out, and both locations would have afforded an unobstructed view of the Eastern sky where the supernova was. Furthermore, calculations suggest the supernova would have appeared close in the sky with the waning crescent moon.
When Miller published his work he acknowledged that his evidence was circumstantial, but that didn’t stop the supernova artwork idea from gaining traction. Over the years numerous other Southwest paintings resembling a crescent moon and star were discovered, and experts quickly linked them with the Crab supernova. But no one bothered to check out the original sites that inspired Miller’s paper—until now.
“These two sites—White Mesa and Navaho Canyon—established a preference that equates star-crescent combos with eyewitness observations of the Crab supernova,” Griffith Observatory Director Ed Krupp said last week in National Harbor, Md., at the 223rd meeting of the American Astronomical Society (AAS). “But an onsite examination had not been undertaken for 50 years.”
Over the past three decades Krupp has sought out every Southwest spot claimed to hold Crab supernova art. But he could not find White Mesa and Navaho Canyon. “I found no one who had been to either site or even knew where they are,” he said. Miller’s report included only vague descriptions of their locations and closely cropped photos that offered no context.
In 2008, Krupp’s sleuthing paid off. He enlisted the help of Museum of Northern Arizona research associates Evelyn Billo and Robert Mark, who found documentation of the sites in the museum’s archives. The group then obtained tribal permits to search within the Navajo Reservation, and mounted expeditions to both sites, which were in remote areas accessible only by off-road driving and long hikes.
The White Mesa painting was in a sheltered cave hollowed out of the face of a tall, eroded rock pinnacle. “At first it is tempting because it is quite distinctive,” Krupp said. “But as you get closer up and take a better view of it questions begin to emerge.” The painting, for example, appeared bright and fresh, in contrast to older prehistoric pictographs on the wall that were clearly faded. The style of the picture seemed modern as well and Krupp found himself questioning whether the image was a star and crescent at all.
After some research, Krupp found that the lines on the wall could just as easily represent a round head (the star) with a horn (crescent) protruding from it, or even a scalping knife. In fact, the horned figure looks a bit like common representations of the Hopi long-horned kachina spirit being called Wupá’ala. “The point is we have very plausible alternate explanations that are consistent with a much more plausible dating for the painting,” Krupp said.
On to Navaho Canyon. There, Krupp and his team had a hard time even seeing the star and moon image because it was embedded into a larger design. “The so-called supernova is neither obvious nor distinctive,” Krupp said. “It’s a relatively small and subdued component of a complex panel.” The tight framing of the painting in Miller’s photograph was highly misleading, the scientists concluded. For example, the “star” in the picture is actually attached to another form that appears to be a figure, and nearby are images of animals, birds, and geometric patterns. If the painting was really meant to commemorate a unique astronomical event, it is unlikely the image would be so buried among other designs that clearly have nothing to do with the supernova, Krupp said.
Krupp’s investigations have ultimately caused him to dismiss all of the connections between Southwest cave paintings and the Crab supernova. “I am certain that star-crescent combos have absolutely nothing to do with the 1054 A.D. event,” he said. While some may indeed be celestial symbols, “their meaning varies with culture and time.”
After Krupp’s talk at the AAS meeting, one astronomer raised his hand to say he was “rather depressed” that the story he has been telling his Astronomy 101 students about the Crab rock art is wrong. But Krupp was sanguine. “Be cheered,” he said. “If it’s not the Crab supernova it’s something else, and that tells us something else about human nature and inquiry and the bond between humans and the sky.”
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