A STAR exploded in the Dark Ages, just a stone鈥檚 throw from the Earth in
astronomical terms. But the astronomers who discovered the remains of the star
say they鈥檙e baffled: why did no one record the supernova, which would probably
have outshone every star in the night sky?
Supernovae, explosions of massive stars at the end of their lives, leave
clouds of hot, glowing gas that spread out over hundreds of years. We know of
around 200 such supernova remnants in our Galaxy, but the last time anyone saw
an explosion in the Milky Way was in 1604.
Now a new supernova remnant has come to light in the southern constellation
Vela. Bernd Aschenbach of the Max Planck Institute for Extraterrestrial Physics
in Garching, Germany, discovered the remnant using data from the German-US ROSAT
satellite. This picked up X-rays from a circular area of sky with a diameter
about 4 times that of the full Moon.
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In this week鈥檚 Nature (vol 396, p 141 and 142), Aschenbach and a
team led by Anatoli Iyudin, also of the Max Planck Institute, report that this
must be a supernova remnant. The stellar remains are very hot, at more than 30
million kelvin, and the researchers conclude that the explosion appeared in the
night sky around 680 years ago, in the early 14th century. Their observations
also show that the supernova lies just 600 light years away. 鈥淭his is the
closest supernova from mankind鈥檚 recent past,鈥� says Aschenbach.
At this distance, the explosion should have been spectacular. 鈥淚t would have
been brighter than every star and planet in the sky,鈥� says Aschenbach. So why
did no one record it? Dust clouds could have dimmed the light, says Aschenbach.
Or perhaps the exploding star was too low on the horizon for the most avid
astronomers of the time鈥攖he Chinese and the Japanese鈥攖o see. He also
notes that the timing of the supernova coincides with a gap in Chinese
astronomical records when China was under Mongolian rule.
鈥淚f it really was that bright, there has to be a record,鈥� says Anthony Aveni,
an expert on early astronomy at Colgate University in Hamilton, New York.
鈥淧erhaps we鈥檙e not looking in the right places.鈥� He suspects references may turn
up in medical texts, as some medieval civilisations used astrology to diagnose
disease.