Posted: Tue, Oct 25, 2011, 7:24 AM ET (1124 GMT)
Astronomers announced Monday they now understand why a supernova witnessed nearly two millennia ago expanded faster than expected. The supernova, designated RCW 86, was witnessed by Chinese observers in 185 AD, making it the oldest recorded observation of a supernova. More recent studies of the supernova remnant showed that it is two to three times bigger than expected. Astronomers used a combination of space-based infrared and x-ray observations to study the supernova remnant, and found that the supernova was caused by material from a nearby star falling onto a white dwarf. That white dwarf, prior to the supernova, had created a cavity relatively free of gas and dust surrounding it, allowing the remnants to expand at a faster rate, and hence the larger size.

Related Links:

•  SPACE.com article
•  AFP article
•  AP article
•  NASA press release