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. We dig into the anomalous expansion rate that pointed to a hidden engine, the discovery of the Crab Pulsar in 1968, electron capture supernovae, synchrotron radiation, the unsolved missing mass problem, and how the nebula’s position near the ecliptic lets scientists use it as a cosmic X-ray backlight.

• How Messier’s search for Halley’s Comet led to the first entry in his catalog of objects to ignore
• Measuring 1,500 kilometers per second of expansion and tracing it back nine centuries
• A city-sized neutron star spinning 30 times per second with a luminosity 148,000 times the Sun
• Why the visible gas and the pulsar add up to only four or five solar masses when the progenitor should have been nine to eleven
• Using transits of the Sun and Saturn’s moon Titan across the nebula to probe the solar corona and Titan’s atmosphere