Peering into the Heart of the Crab Nebula. In 1054 AD, Chinese astronomers were startled by the appearance of a new star, so bright it could be seen in broad daylight for several weeks. Today, the Crab Nebula is what's left of the supernova explosion they witnessed, Peering into the Heart of the Crab Nebula. Credit: NASA, ESA, and K. Sahu (STScI) (NASA Media Archives). Buy this as a superb wall poster, a canvas print or a framed print.