PHOENIX – A petroglyph near Phoenix may by the only record in the Western Hemisphere of a supernova that appeared in 1006 — the brightest supernova visible from earth for more than 5,000 years.
John Barentine, who works at the Apache Point Observatory in Sunspot, N.M., presented his theory Monday at the American Astronomical Society meeting in Calgary, Alberta.
The supernova appeared in the constellation Lupus, a little below and west of the well-known constellation of Scorpius, the scorpion.
"What particularly got my attention about that rock and the glyphs on it was the representation of what is pretty obviously a star, and a bright star at that. And the figure of a scorpion. Scorpions appear in rock in the Southwest but are not a very common motif," Barentine said.
The petroglyph panel in the White Tank Mountains west of Phoenix consists of several figures pecked into the dark desert varnish, a patina of iron and manganese oxides that often coats rock in arid environments.
The most prominent figures are an eight-point star and an irregular circle, from which several rays, or arms, protrude.
According to Barentine, the star represents the great supernova of 1006 and the irregular circle, with arms and perhaps eyes, is the constellation Scorpius. Other figures on the rock may represent nearby star patterns.
Todd Bostwick, archaeologist for Phoenix and an expert on Hohokam culture and archaeoastronomy, said it is difficult to correlate a specific celestial event to a single piece of rock art.
"There are many images out there that could be interpreted as star bursts or suns or planets, so you have to be very cautious about [Barentine's theory]" he said.
A supernova is the cataclysmic explosion that marks the end of a star's life. From Earth, it appears as if a new star suddenly appears in the sky and then, over the course of a few weeks, or months, fades away.
Astronomers say the supernova of 1006 was brighter than any visible from Earth for at least 5,000 years.
Although it is impossible to date specific petroglyphs with an accuracy of more than a few hundred years, archaeologists know that the Hohokams lived in the area at the time of the supernova. Like all subsistence farmers, they observed the night sky to track the seasons.
"They saw something, they knew it was significant and they were moved to record it," Barentine said. "In an age before science, they were scientists."