Almost 1615 years ago, Chinese astronomers saw a brilliant new star appear in the constellation we now call Sagittarius. Last fall, NASA's Chandra X-ray Observatory identified the stellar corpse of this supernova explosion: a tiny, superdense, spinning, x-ray- emitting neutron star, or pulsar. According to Vicky Kaspi of McGill University in Montreal, this is only the second pulsar for which an accurate age is known. The other, in the Crab Nebula, resulted from a supernova recorded in A.D. 1054 by Asian stargazers.
The Chandra image shows the pulsar as a white spot in the center of a hot, gaseous shell ejected by the dying star. This supernova remnant, some 15,000 light-years away, was already believed to be associated with the explosion seen by Chinese astronomers in the spring of A.D. 386. But earlier studies had suggested that it was separate from the shell and far older--by 23,000 years. By showing that the pulsar is smack in the middle of the remnant, Chandra has proved it was indeed the light seen in China. It has also shown, says Kaspi, that there's something wrong with the standard way of determining pulsar ages.
The Gum Nebula is a huge constellation in the Southern hemisphere, about 1000 light years away, and extending over at least 40 degrees of the sky. The Gum Nebula is thought to be the remnant of one or more ancient supernovae. One pulsar in this region, perhaps not associated with the Gum Nebula, is the Vela Pulsar, which is about 800 light years away and estimated to be about 11,000 years old. (By comparison, the Crab Nebula is about 6,500 light years away.) However, if the dating of pulsars is wrong, then the Vela Pulsar could be much younger, and may have arisen only 4,500 years ago, or about the time of the Flood. The Vela supernova remnant is now about 230 light years across and covers over 100 times the sky area of the full moon. (See Vela Supernova Remnant in X-ray. An image of the Vela Pulsar itself may be found here. A map of how all these features relate to the sun is found here.) Perhaps intense radiation from this supernova caused the flood, and even triggered the asteroid impacts that are thought to have influenced mass extinctions.
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