When Gum Glowed

The journal Archaeology usually concerns itself with down-to-earth matters, but a recent issue contains an appeal that reaches rather far out. In a letter to the magazine, Astronomers John C. Brandt, Stephen P. Maran and Theodore Stecher ask archaeologists for help in determining the age of a giant celestial gas cloud. Known as the Gum Nebula, the cloud has been attracting more than usual attention among astronomers. At its center, some 1,500 light-years away from earth, they have discovered a pulsar --a neutron star that emits regularly spaced radio signals. What possible information could archaeologists offer? Quite a bit, the astronomers explain. Both the Gum Nebula and pulsar are remnants of a relatively rare heavenly event: a supernova, the cataclysmic explosion of a massive dying star. The astronomers point out that another supernova, the one that created the familiar Crab Nebula and its pulsar, was witnessed by the Chinese in A.D. 1054 and was well documented in their records. The same event was seen in North America and recorded at the same time in cave and cliff drawings found in northern Arizona.

The Gum Nebula supernova occurred much earlier--about 9000 B.C., according to estimates based on the current signal rate of Gum's pulsar. The sudden and brief appearance at that time of what seemed to be a new and brightly glowing star--probably as luminous as a quarter moon and visible even during full daylight--may have sufficiently moved a primitive sky-gazer to scrawl or carve his impressions on a cave wall. And if an archaeologist should ever find such a drawing, its age could be determined by using radioactive "clocks" and other dating methods on other objects at the site. Once that was done, scientists would know more precisely the time of Gum's celestial spectacular.

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