According to the Book of the Later Han; a history of China from 25 to 22 A.D., a new object appeared in the night sky in the year 185 A.D. This new object was described as the size of “half a bamboo mat“, and it “displayed various colors.”
For 8 months this ‘guest star’ sparkled, but finally faded and disappeared. It was never seen again.
What the Chinese recorded wasn’t a star, but the remnants of exploded star called a Supernova.
A collapsed star
A star goes Supernova when it burns through all of its fuel and collapses on itself. Its core heats to a billion degrees and creates gamma rays and a huge amount of neutrinos. Only a fraction of these neutrinos were absorbed by stellar gas and the resulting explosion ripped apart the outer layers of the star. Anything nearby, such as planets, would have been wiped out in a blink of an eye.
The Supernova was brighter than an entire galaxy. So, it’s no wonder that the people of Earth could see it without a telescope. Plus light pollution was fairly non-existent. So, SN 185 probably looked a heck of a lot brighter than it would today in the night sky.
RCW 86 – The remnants of SN 185
Scientists of today have determined that a known supernova remnant by the name of RCW 86, is actually the leftovers of SN 185. They calculated how fast the shell of the remnant was moving and determined that the supernova happened about 2,000 years ago. The placement of the SN 185 in the sky also matched the historic records.
So, do you think we’ll see a Supernova anytime soon? They happen about 3 times a century in our Milky Way galaxy. The most likely contenders are red supergiants Antares and Betelguese. Betelguese is the 2nd brightest star in Orion and the nearest red supergiant star to Earth. Although there was an initial excitement when it started dim recently, it’s since become bright again. But when it does go it will be most likely visible with the naked eye.