About 11,000 years ago, a star went supernova. The light from this event first reached Earth around A.D. 1667. There are no records of anyone noticing probably because large amounts of dust between the dying star and Earth obscured our view of the explosion.
The remnants of this supernova was finally noticed in 1947 by radio astronomers. Now known as Cassiopeia A, it is one of the brightest radio sources in the whole sky. More recently, the Wide-field Infrared Survey Explorer (WISE) was used to observe the infrared echoes from the supernova.
When WISE took this image, the blast wave had expanded out to about a distance of 21 light-years, but he flash of light from the explosion, traveling at the speed of light, had covered well over 300 light-years. The orange-colored echoes further out from the central remnant have been reflected from interstellar dust that was heated by the supernova flash centuries after the original explosion.
Image Credit: NASA / JPL / UCLA