The story
On July 4, 1054, Chinese astronomers in the Song capital noted a guest star near the star Tianguan, in the constellation Taurus. Official records say it was visible in daylight for 23 days and in the night sky for 653 days, until April 1056. Japanese sources also mention it, and some scholars think Arab observers did, but no clear European record has been found. To Chinese court astronomers it was an omen to be reported to the emperor.
Centuries later, in 1731, John Bevis found a faint nebula at the same place. In 1758 Charles Messier, hunting for Halley's Comet, mistook it for a comet and decided to list such objects so no one else would be fooled, making it the first entry in his catalog, M1. In 1844 Lord Rosse sketched it with tentacles and called it the Crab. In the 1920s astronomers measured that the Crab was expanding, and wound the motion back to about 900 years, pointing to 1054. In 1942 Jan Oort and Nicholas Mayall confirmed the link, and in 1968 radio astronomers found a pulsar in the Crab, a rapidly spinning neutron star left by the exploded star.
The explosion was a core-collapse supernova, the death of a massive star. The Crab is now one of the most studied objects in the sky and a standard calibration source for X-ray telescopes. It is also the clearest case where an ancient record, a nebula and a collapsed star all trace back to the same event.
Why it mattered
- Proved that a historical guest star could be matched to a modern remnant, setting a method for dating supernova remnants.
- Led to the identification of pulsars as spinning neutron stars, via the Crab pulsar found in 1968.
- Inspired Messier's catalog, which began with the Crab Nebula, M1.
- Made the Crab a standard light source that astronomers use to calibrate X-ray and gamma-ray instruments.
Sources
- Benchmarks: July 4, 1054: Birth of the Crab Nebula EARTH Magazine
- Crab Nebula NASA
- July 4, 1054: The Crab Nebula supernova explodes Astronomy Magazine
- Supernova Pictograph High Altitude Observatory, UCAR
Contested history
Consensus: Chinese and Japanese records describe a supernova in 1054, and the Crab Nebula and its pulsar are its remnant; a few other claims about the star are less secure.
- Crab Nebula NASA
- Benchmarks: July 4, 1054 EARTH Magazine
- Supernova Pictograph High Altitude Observatory, UCAR
- Crab Supernova Rock Art (Krupp, Journal of Skyscape Archaeology) Journal of Skyscape Archaeology
- Benchmarks: July 4, 1054 EARTH Magazine
- The Historical Supernovae arXiv
Community notes
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