Scientists are agog over the brightest exploding star in 383 years

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The Crab supernova was, at its brightest, as brilliant as the planet Venus and visible during the daytime; its appearance was noted not only by the Chinese and Japanese but possibly also by Indians in the American Southwest. The New World evidence comes in the form of images carved and painted on rock walls in northern Arizona showing a celestial object adjacent to a crescent moon. There is no proof that this primitive artwork represents the supernova, but archaeological dating techniques show the Indians were in the area when the star flared, and astronomers have calculated that the supernova indeed appeared in the sky very close to the crescent moon.

Europeans left no known record of the Crab supernova, although some probably saw it, and no evidence has been found that they saw an 1181 stellar explosion. It was not until November 1572 that Europe joined the fraternity of distinguished supernova recorders. Although Danish Astronomer Tycho Brahe was not the first to spot the new star that appeared in the constellation Cassiopeia, he ensured that posterity would associate his name with it by writing a book titled De Nova Stella (Concerning the New Star).

The next supernova to be seen by the naked eye happened only 32 years later, in 1604, in the constellation Ophiuchus, and its best-remembered witness was Brahe's former assistant Johannes Kepler. Unlike most supernovas, this one was seen before it reached maximum brightness, so Kepler's descriptions of the blazing star are of particular interest to astronomers. His observations would have been even more detailed and valuable had they been made with a telescope. Unfortunately, the star's timing was off. The supernova lighted the night skies just a scant five years before Galileo made the first documented telescopic scan of the heavens, discovering mountains on the moon and spots on the sun.

If the previous 1,800 years of astronomical history are any guide, astronomers say, a supernova visible to the naked eye should occur in or near the Milky Way galaxy four times every thousand years or so. But from 1604 to 1987, none were recorded. (The supernova of 1885, just on the threshold of visibility in the night sky, took place in the Andromeda galaxy, 2.2 million light-years away.) To be sure, many stars flared up during this interval. But astronomers now know they were not supernovas but nearby novas. These are shorter-lived events, caused by the sudden explosion of gases in a class of stars known as white dwarfs, that release only one ten-thousandth the energy of a supernova.

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