Supernova!

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It was a glacial period, and in southern Africa the climate was cooler than it is today. Giraffes, hyenas and baboons abounded, along with now extinct giant horses and hartebeests and buffalo with 13-ft. horn spans. Neanderthal man had not yet emerged, but intelligent beings already roamed the savanna, upright creatures known today as archaic Homo sapiens, who could fashion crude axes, picks and cleavers out of stone. On a clear night 170,000 years ago, one of these ancestors of man may have looked up at a milky band of stars stretching across the sky, his eyes pausing briefly on a patch of light that seemed to have broken away from the band.

At that moment, in the distant patch -- actually a small galaxy now known as the Large Magellanic Cloud -- a supergiant star glowed fiercely, showing no outward signs of its impending doom. Suddenly, in a cataclysmic blast, it exploded, brightening until it outshone a hundred million stars the size of the sun. In every direction the intense light, traveling at 186,282 miles per second, radiated out into the universe, some of it heading toward a minor planet orbiting an average star in the neighboring and much larger Milky Way galaxy.

Some 170,000 years later, on that minor planet, man had evolved, developed technology, built great cities and, in an effort to better understand his place in the universe, developed great instruments that could peer deep into space. It was not until then, on the night of Feb. 23, 1987, that the first light emitted by the exploding star, having traveled a billion billion miles through space, finally reached the earth. Some of the light passed through the lens of a 10-in. telescope at Las Campanas Observatory on a windblown 8,000- ft. mountaintop in northern Chile and was reflected into a camera set up by Ian Shelton, a Canadian astronomer. Shelton, 29, assigned to the observatory by the University of Toronto, had been taking long exposures of the Large Magellanic Cloud (LMC), a task that occupied him until 2:40 a.m. on Feb. 24. Recalls Shelton: "I decided enough was enough. It was time to go to bed." But before turning in, he made up his mind to develop the last photographic plate. Lifting the plate from the developing tank, he scrutinized it, then stopped short. There, near a feature within the LMC known as 30 Doradus, or the Tarantula nebula, was an unfamiliar bright spot.

"I was sure that there was some plate flaw on it," Shelton says, "but it was no flaw." He walked outside, looked up at the Large Magellanic Cloud and, without a telescope or binoculars, clearly saw the exploding star, or supernova. While hundreds of supernovas occurring in incredibly distant galaxies have been spotted by powerful telescopes, this was the first one visible to the naked eye since 1885. More important, at a distance of only 170,000 light-years, it was the brightest one to appear in terrestrial skies since 1604.