Crab Nebula

The Crab Nebula (M1, Messier 1, NGC 1952, Tauras A) is a supernova remnant for a supernova recorded in 1054 (SN 1054). It is the prototype for an appearance-type of SN remnants termed a crab-type remnant. Charles Messier discovered the nebula in 1731, mistaking it for Halley's Comet until he established that it wasn't moving, which inspired him to create a catalog of astronomical objects that could be mistaken for comets (Messier Catalog). At about the center of the Crab Nebula is a pulsar (the Crab Pulsar, PSR B0531+21) with a pulse frequency of 30/second, one of the rare pulsars that have also been identified optically, and also unique in that its age is known down to the year. Crab Nebula characteristics:

• Taurus - constellation.
• 05h34m31.94s - right ascension.
• +22deg00m52.2s - declination.
• 6500 ly - distance.
• +8.4 - apparent magnitude.
• 7 arcmin - apparent dimension (angular diameter).

The Crab Nebula has been much studied, being useful in gathering data and testing models. For example, when pulsars were first discovered, it was predicted that a pulsar would be found in the Crab Nebula, and one's subsequent discovery helped confirm the model that pulsars are spinning neutron stars formed from supernovae.