The Crab Nebula is a supernova remnant in Taurus---NOT in Cancer---early observer William Parsons, 3rd Earl of Rosse (1800--1867) thought it looked like a crab at one time and the name stuck.

It is in the Milky Way at 2.0 ± 0.5 kpc away. Its longest dimension is about 3.4 pc.

The Crab Nebula is classified as a pulsar wind nebula. The wind consists of charged particles accelerated by the strong magnetic field of the Crab Pulsar (mass 1.4 M_☉, radius about 10.5 km, rotational period 33.5028583 ms).

The Crab Pulsar is the neutron star which was created by the Galactic core-collapse supernova SN 1054. The Crab Pulsar is probably visible in the image as a faint star if you knew where to look.

SN 1054 exploded in year 1054 (discovery Jul04) and was recorded in China, Japan, and Iraq.

Its peak apparent magnitude in V (which probably occurred in 1054 July) is estimated to be -6 which makes it 100 times brighter than Sirius.

No one in Europe left a record of SN 1054---were they agog about Scotland---the historical MacBeth (died 1057) was defeated circa July of that year at Dunsinane---but he did NOT die then (pace William Shakespeare (1564--1616)).

Credit/Permission: NASA, ESA, Jeff Hester, A. Loll, 2005 (uploaded to Wikipedia by User:User:DragonFire1024, 2006) / Public domain.
Image link: Wikipedia: File:Crab Nebula.jpg.
Local file: local link: crab_nebula.html.
File: Neutron star file: crab_nebula.html.