Supernova RCW 86 Mystery Solved with Spitzer and WISE
In AD185, a guest star amused the Chinese astronomers of the time for an eight month spell. One of several supernovae that the advanced civilisation peered at over their history had illuminated their erudite books with heavenly light. In fact, we have known for a while it was RCW 86, but now we have an idea about how far the explosion spread and how a white dwarf was involved. Yet again, for the umpteenth time recently, those new telescopes have opened our eyes. No, it's not the Chilean observatories, this is an eight-year-old, wandering about after the Earth, on a heliocentric orbit. It's Spitzer (of course, you knew that), sitting on a "bus" getting a great view of infra-red, along with its friend, WISE., which was launched in 2009 for a six month survey of the entire sky!
Previous data from NASA's Chandra X-ray Observatory and the European XMM-Newton Observatory were used to provide the image and help with the research. Brian J. Williams, an astronomer at North Carolina State University in Raleigh. Williams is lead author of this study. He explained, "This supernova remnant got really big, really fast." He knows that the star was much bigger than most supernovae and found the reason was that a cavity enclosed the stellar explosion, causing debris to be expelled much further and faster than would have otherwise been possible. Below is an artistic impression of how this supernova might have appeared to the early astronomers.
Bright stars in space via Shutterstock
Of course, this research has pinpointed exactly how it worked out. A Type 1a supernova like this shrinks into a dense white dwarf star. Then it siphons off fuel of some kind from a neighbouring star and explodes into a "full moon size" RCW 86. That is truly big, by even superstar standards.
Spitzer and WISE, that intrepid pair, also allowed the research team to measure the present dust temperature of RCW86 at -200 oC (or -325 oF). This shows the amount of gas remaining in the cavity or fragment must be low. Chandra and XMM-Newton had already contributed the information that iron content was high, again showing that type 1a was the correct diagnosis. Believe it or not, there are more powerful supernovae, which could also have created such a large mess.
"Modern astronomers unveiled one secret of a two-millennia-old cosmic mystery only to reveal another," said Bill Danchi, Spitzer and WISE program scientist at NASA Headquarters in Washington. He reckons he's just as much in awe of cosmic events as the ancient Chinese. But if they would have had the technology, just imagine what fireworks there would have been!
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