In the year 1054 a star exploded so brightly that Chinese astronomers recorded it shining in broad daylight for more than three weeks, and the wreckage of that blast is still expanding across the sky today as the Crab Nebula.

In the year 1054 a star exploded so brightly that Chinese astronomers recorded it shining in broad daylight for more than three weeks, and the wreckage of that blast is still expanding across the sky today as the Crab Nebula.

On 4 July 1054, astronomers in Song dynasty China recorded a new point of light near the southern horn of the constellation we call Taurus. They called it a guest star, the term they used for a star that appeared where none had been. It was bright enough to be seen in full daylight for 23 days, and it remained visible at night for around 21 months before fading. The expanding debris from that explosion is still spreading across the sky, and we n…