On July 4, 1054, a new star appeared in the daytime sky, outshining Venus for nearly a month and lingering at night for almost two years. This episode follows the remnant of that explosion, the Crab Nebula, from its accidental rediscovery by comet hunters in the 1700s to its role as a modern astrophysical laboratory. We cover John Bevis's 1731 sighting, Charles Messier's frustration at a fuzzy patch in Taurus that refused to move, and how that annoyance produced the Messier catalog with M1 as its first entry. We also explain why the Earl of Rosse's inaccurate sketch gave the nebula a name that never fit.

From there we look at how astronomers used photographic plates and a blink comparator to measure the nebula's expansion, rewound the math to 1054, and matched it to records from the Song Dynasty, a Japanese poet, and a physician in Baghdad. ...