The Crab Nebula is the wreckage of a star seen shining by day in 1054
In July 1054 Chinese astronomers logged a guest star in Taurus bright enough to see in daylight. It stayed visible without a telescope for about two years, then faded. Nearly nine centuries later, astronomers traced a glowing, expanding cloud back to that very spot and date, making it the first remnant tied to a recorded supernova.
The explosion probably appeared in April or early May and peaked by July, outshining everything in the night sky except the Moon, Venus included. Japanese observers recorded it too, and a mention by the Baghdad physician Ibn Butlan turned up only in 1978, surviving in a 13th-century copy. Accounts from Native American and Arab stargazers are also linked to it.
The cloud itself had a long, confused career in catalogues. John Bevis spotted it in 1731. Charles Messier stumbled on it in 1758 while hunting for the predicted return of Halley's Comet in Taurus, briefly mistook it for the comet, and made it the first entry in his list of comet-like objects, which is why it is also called M1. Around 1842 Lord Rosse sketched it through a 36-inch telescope at Birr Castle with limbs like a crab's. A bigger telescope later failed to show the resemblance, but the name stuck.
Connecting cloud to star took the 20th century. Photographs taken years apart showed the nebula growing, and running the expansion backwards put its birth roughly 900 years earlier. Carl Lampland reported structural changes in 1921, Edwin Hubble proposed the 1054 link in 1928, and Nicholas Mayall later confirmed it. The match launched a search that has since paired seven other remnants with historical sightings.
At its heart spins the Crab Pulsar, a neutron star about 28 to 30 kilometres wide turning 30.2 times a second. Franco Pacini predicted it, and its discovery in 1968 proved pulsars are rotating neutron stars. The nebula sits about 6,500 light-years away, spans around 11 light-years and expands at roughly 1,500 kilometres per second. Its steady glow is useful as a backlight: astronomers mapped the Sun's corona with its radio waves and in 2003 gauged the atmosphere of Saturn's moon Titan as it blocked the nebula's X-rays.
Source: Crab Nebula
