Prehistoric Native Americans may have carved a record of a supernova explosion that appeared in the skies a millennium ago into a rock in Arizona, US.

John Barentine, an astronomer at the Apache Point Observatory in New Mexico, came across the carving while hiking in the White Tank Mountain Regional Park in Arizona.

It depicts a scorpion and an eight-pointed star. "I had just been reading about the supernova of AD 1006 and I knew it appeared in the constellation Scorpius, so the connection flashed into my mind."

To make his case, Barentine and his colleague Gilbert A. Esquerdo, at the Planetary Science Institute, Tucson, used planetarium software to recreate the sky as it would have appeared in Arizona during the supernova's appearance and overlaid it with photographs from the site.

The supernova would have been brighter than a planet, and both it and the constellation - which is shaped like a scorpion - would have appeared just above the edge of the rock, in the same orientation depicted in the carvings. Native Americans populated the region during that period and often recorded objects thought to have magical powers, says Barentine.

"It's by no means conclusive, but I think it's strong circumstantial evidence that the art depicts the supernova," says Barentine. He announced his theory at the American Astronomical Society Meeting in Calgary, in Alberta, Canada, on Monday.

Star watchers

The supernova was recorded by star watchers in Asia, the Middle-East and Europe. But until now, nobody thought that prehistoric Native Americans followed events in the sky. "I don't think enough credit has been given to the ancient Native Americans in the past, but that might change now," Barentine told New Scientist.

If the art does represent the supernova, it would provide a useful date to help work out the age of neighbouring rock carvings, which are difficult to assess by other methods, says Barentine.

But the White Tank Mountain is not the first suspected supernova petroglyph in North America. A petroglyph at Chaco Canyon National Monument in New Mexico may depict the supernova of 4 July 1054.

Another petroglyph at White Tank may also be a recording of the AD 1054 supernova. White Tank Mountain park ranger Mark Lansing says that petroglyph looks like colliding suns and is nestled in a back canyon along with pictures of other celestial objects.

"The AD 1006 petroglyph is a little more abstract," Lansing says of Barentine's find. "I'd seen his petroglyph but not really related it to the sky for 1006. He does show what the sky may have looked like in AD 1006."