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The '''Crab Nebula''', also know as '''M1''' and '''NGC 1952''', is an expanding gas cloud surrounding a [[neutron star]] located in the constellation of [[Taurus]] near the star [[Zeta Tauri]], the south horn of the bull. Possibly the most famous [[nebula]], it is the result of a [[supernova]] event that was first observed on [[Earth]] in 1054 A.D.  Since then, the nebula has been expanding at a rate of 1500 km/s and is now on average some 11 light years in diameter<ref>http://apod.nasa.gov/apod/ap011227.html</ref>.

The '''Crab Nebula''', also know as '''M1''' and '''NGC 1952''', is an expanding gas cloud surrounding a [[neutron star]] located in the constellation of [[Taurus]] near the star [[Zeta Tauri]], the south horn of the bull. Possibly the most famous [[nebula]], it is the result of a [[supernova]] event that was first observed on [[Earth]] in 1054 A.D.  Since then, the nebula has been expanding at a rate of 1500&nbsp;km/s and is now on average some 11 light years in diameter.<ref>http://apod.nasa.gov/apod/ap011227.html</ref>

==Supernova Event==

==Supernova Event==

The Crab Nebula is the result of the supernova event called '''SN1054''', which was first recorded by [[Chinese]] and [[Arab]] astronomers on July 4th, 1054 A.D. as a "guest star".  The event was possibly also the inspiration for astronomy-related art created by [[Anasazi]] [[Indians]].<ref>http://www.astronomy.pomona.edu/archeo/outside/chaco/nebula.html</ref> Initially the supernova had an apparent magnitude of -6, making it brighter then even [[Venus]].  The star then began to fade, but remained subsequently bright enough to be observed during the day for the next 23 days, and at night for the next 653 days before finally fading from view.<ref>http://www.seds.org/messier/more/m001_sn.html</ref> The supernova has been classified since with the variable star designation '''CM Tauri'''.  

The Crab Nebula is the result of the supernova event called '''SN1054''', which was first recorded by [[Chinese]] and [[Arab]] astronomers on July 4, 1054 A.D. as a "guest star".  The event was possibly also the inspiration for astronomy-related art created by [[Anasazi]] [[Indians]].<ref>http://www.astronomy.pomona.edu/archeo/outside/chaco/nebula.html</ref> Initially the supernova had an apparent magnitude of -6, making it brighter then even [[Venus]].  The star then began to fade, but remained subsequently bright enough to be observed during the day for the next 23 days, and at night for the next 653 days before finally fading from view.<ref>http://www.seds.org/messier/more/m001_sn.html</ref> The supernova has been classified since with the variable star designation '''CM Tauri'''.  

Based on theoretical models of supernova explosions, the progenitor star for the explosion is calculated to have been between 9 and 11 solar masses.<ref>http://adsabs.harvard.edu/abs/1985cnrs.work...97N</ref>

Based on theoretical models of supernova explosions, the progenitor star for the explosion is calculated to have been between 9 and 11 solar masses.<ref>http://adsabs.harvard.edu/abs/1985cnrs.work...97N</ref>

==Properties==

==Properties==

Despite being one of the best known nebulae, the Crab Nebula is invisible to the unaided eye, with an apparent magnitude of only +8.4  The exact distance of the nebula itself is unknown. It is roughly 11 light years across overall, extending some 13 light years across at its longest.  Right now the nebula's gasses are expanding at around 1500 km/s, and it is believed that this velocity is increasing due to energy emitted from the pulsar. The amount of matter in the nebula is estimated to be around 4.6 ± 1.8 solar masses, and is used to help estimate the total mass of the progenitor star.<ref>http://adsabs.harvard.edu/abs/1997AJ....113..354F</ref>

Despite being one of the best known nebulae, the Crab Nebula is invisible to the unaided eye, with an apparent magnitude of only +8.4  The exact distance of the nebula itself is unknown. It is roughly 11 light years across overall, extending some 13 light years across at its longest.  Right now the nebula's gasses are expanding at around 1500&nbsp;km/s, and it is believed that this velocity is increasing due to energy emitted from the pulsar. The amount of matter in the nebula is estimated to be around 4.6 ± 1.8 solar masses, and is used to help estimate the total mass of the progenitor star.<ref>http://adsabs.harvard.edu/abs/1997AJ....113..354F</ref>

===Crab Pulsar===

===Crab Pulsar===

The '''Crab Pulsar''' is a a rapidly rotating [[neutron star]] some 28-30 kilometers in diameter, and has a mass twice that of the [[Sun]]. <ref>http://adsabs.harvard.edu/abs/2002A%26A...396..917B</ref>  The pulsar rotates once every 33 milliseconds, emitting radiation towards us once per rotation.  This allows us to measure its rotational speed at 6.4 million km/h.  The pulsar is slowing down though, rotating 15 microseconds slower each year.  The [[radiation]] emitted though from the remnant pulsar is enough to illuminate the entire Crab Nebula with a total luminosity some 75,000 time greater then our Sun.<ref>http://www.solstation.com/x-objects/crab-neb.htm</ref>

The '''Crab Pulsar''' is a a rapidly rotating [[neutron star]] some 28-30 kilometers in diameter, and has a mass twice that of the [[Sun]].<ref>http://adsabs.harvard.edu/abs/2002A%26A...396..917B</ref>  The pulsar rotates once every 33 milliseconds, emitting radiation towards us once per rotation.  This allows us to measure its rotational speed at 6.4 million km/h.  The pulsar is slowing down though, rotating 15 microseconds slower each year.  The [[radiation]] emitted though from the remnant pulsar is enough to illuminate the entire Crab Nebula with a total luminosity some 75,000 time greater then our Sun.<ref>http://www.solstation.com/x-objects/crab-neb.htm</ref>

[[Category:Astronomy]]

[[Category:Astronomy]]