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An image combining data from four different space telescopes shows the remains of a supernova observed by the Chinese almost 2,000 years ago. (NASA/ESA/JPL-Caltech/UCLA/CXC/SAO )

Astronomers finally know why the first documented supernova was super-sized.

The exploded star was observed by the ancient Chinese in the year 185 A.D., and visible for eight months. It was later found to be a bigger-than-expected supernova remnant, 8,000 light years away.

New observations in the infrared show the explosion took place in a cavity in space. The cavity allowed the stellar shrapnel to shoot faster and farther out into the universe.

The star — similar to our sun — died peacefully and turned into a dense white dwarf. It sucked up material from another star, and then exploded in a supernova.

NASA announced the findings Monday. Four space telescopes were used in the study.