The ancient mystery of a bright exploding star has been solved by Nasa scientists.
Nearly 2,000 years ago, in A.D. 185, Chinese astronomers spotted a "guest star" which appeared suddenly and remained in the night sky for 8 months.
Now infrared observations by Nasa's Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) show that the mysterious "guest star" was actually the first supernova ever recorded.
"This supernova remnant got really big, really fast," said Brian J. Williams, an astronomer at North Carolina State University in Raleigh. Williams is lead author of a new study detailing the findings online in the Astrophysical Journal. "It's two to three times bigger than we would expect for a supernova that was witnessed exploding nearly 2,000 years ago. Now, we've been able to finally pinpoint the cause."
The reported star was a modern mystery too. By the 1960s, scientists had confirmed that that the celestial guest was the first documented supernova, RCW 86, located around 8,000 light-years away from earth, but it's shape was strangely large.
It wasn't until infrared observations by made Spitzer and WISE could be combined with previous data from Nasa's Chandra X-ray
Observatory and the European Space Agency's XMM-Newton Observatory, that scientists could confirm it was a white dwarf star.
The white dwarf is thought to have later blown up in a supernova after siphoning matter, or fuel, from a nearby star, creating the magnificent display noted by the Chinese.
Bill Danchi, Spitzer and WISE program scientist at NASA Headquarters in Washington said: "Modern astronomers unveiled one secret of a two-millennia-old cosmic mystery only to reveal another,"
"Now, with multiple observatories extending our senses in space, we can fully appreciate the remarkable physics behind this star's death throes, yet still be as in awe of the cosmos as the ancient astronomers."