Changes

==Properties==

==Properties==

Despite being one of the best known nebula, the Crab Nebula isn't visible to the unaided eye with an apparent magnitude of only +8.4  The exact distance of the nebula itself is uncertain but is estimated around 6,500 ± 1,600 light years away.  It is roughly some 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 is believed accelerating due to energy emitting 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 nebula, the Crab Nebula isn't visible to the unaided eye with an apparent magnitude of only +8.4  The exact distance of the nebula itself is uncertain but is estimated around 6,500 ± 1,600 light years away.<ref>http://adsabs.harvard.edu/abs/2008arXiv0801.1142K</ref> It is roughly some 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 is believed accelerating due to energy emitting 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===