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KS update 1.1
#REDIRECT [[Crab nebula]]
{{Infobox nebula
| name = Crab Nebula
| image = Crab Nebula.jpg
| caption = [[Hubble Space Telescope]] mosaic image assembled from 24 individual [[Wide Field and Planetary Camera 2]] exposures taken in October 1999, January 2000, and December 2000
| type = supernova remnant
| epoch = [[J2000.0]]
| ra = {{RA|05|34|31.94}}<ref name="simbad">{{cite simbad |title=M 1 |accessdate=12 February 2012}}</ref>
| dec = {{DEC|+22|00|52.2}}<ref name="simbad" />
| dist_ly = {{val|6500|1600}}
| dist_pc = {{val|2000|500}}<ref name="Kaplanetal2008">{{cite journal |last1=Kaplan |first1=David L. |last2=Chatterjee |first2=S. |last3=Gaensler |first3=B. M. |last4=Anderson |first4=J. |title=A Precise Proper Motion for the Crab Pulsar, and the Difficulty of Testing Spin-Kick Alignment for Young Neutron Stars |journal=[[The Astrophysical Journal]] |volume=677 |issue=2 |pages=1201–1215 |date=2008 |arxiv=0801.1142 |doi=10.1086/529026 |bibcode=2008ApJ...677.1201K}}</ref>
| appmag_v = +8.4
| size_v = 420″ × 290″
| constellation = [[Taurus (constellation)|Taurus]]
| radius_ly = ~5.5
| radius_pc = ~1.7<ref name="Hester2008">{{Cite journal |last1=Hester |first1=J. J. |title=The Crab Nebula: An Astrophysical Chimera |journal=Annual Review of Astronomy and Astrophysics |volume=46 |pages=127–155 |date=2008 |doi=10.1146/annurev.astro.45.051806.110608 |bibcode=2008ARA&A..46..127H}}</ref>
| absmag_v = {{val|p=−|3.1|0.5}}{{Ref label|C|c|none}}
| notes = [[Optical pulsar]]
| names = Messier 1, NGC 1952, Taurus A, [[Sharpless catalog|Sh]]2-244<ref name="simbad" />
}}
The '''Crab Nebula''' (catalogue designations [[Messier object|M]]1, [[New General Catalogue|NGC]] 1952, Taurus A)<ref>catalogue designations [[Messier object|M]]1, [[New General Catalogue|NGC]] 1952, Taurus A</ref> is a [[supernova]] remnant and '[[pulsar]] wind nebula' in the [[constellation]] of [[Taurus (constellation)|Taurus]]. The [[nebula]] was observed by [[John Bevis]] in 1731; it corresponds to a bright [[supernova]] recorded by [[China|Chinese]] and [[Islamic]] astronomers in 1054. In 1840, astronomer [[William Parsons]] gave it the name it has today.<ref>{{cite journal|last=Parsons|first=William|date=1844|title=Observations on Some of the Nebulae|url=https://archive.org/stream/jstor-108366/108366#page/n5/mode/2up|volume=134|at=fig. 81, plate xviii, p. 321|doi=10.1098/rstl.1844.0012|jstor=108366|work=Philosophical Transactions of the Royal Society of London}}</ref>
The nebula is about 6,500 [[light-year]]s (2 [[parsec|kpc]]) from [[Earth]]. It has a diameter of 11 [[light-year|ly]] (3.4 [[parsec|pc]]) and expands at a rate of about 1,500 kilometers per [[second]]. It is part of the [[Perseus Arm]] of the [[Milky Way Galaxy]].
At the center of the nebula lies the '''Crab pulsar''', a [[pulsar|neutron star]] (or spinning ball of neutrons), 28–30 km across,<ref>
{{cite web
|title=Crab Nebula: the spirit of Halloween lives on as a dead star creates celestial havoc
|url=http://chandra.harvard.edu/photo/2006/crab/
}}</ref> which emits pulses of [[radiation]] from [[gamma ray burst]]s to [[radio wave]]s with a spin rate of 30.2 times per second. The nebula was the first astronomical object identified with a historical supernova explosion.<ref name="Mayall"/>
The nebula acts as a source of radiation for studying celestial bodies between it and us. In the 1950s and 1960s, the [[Sun]]'s [[corona]] was mapped from observations of the Crab's radio waves passing through it, and in 2003, the thickness of the atmosphere of [[Saturn (planet)|Saturn]]'s moon [[Titan (moon)|Titan]] was measured as it blocked out [[X-ray]]s from the nebula.
The cloudy remnants of SN 1054 are now known as the Crab Nebula. The nebula is also referred to as Messier 1 or M1, being the first [[Messier catalogue|Messier object]] catalogued in 1758.
== Energy levels ==
Previous analysis showed that with [[X-ray]] and [[gamma ray]] energies above 30 [[Electronvolt|keV]], the Crab is the strongest [[wikt:persistent|persistent]] source in the sky. Its [[flux]] (energy emission) was known to be above 10<sup>12</sup> [[electron volt|eV]].
However, recent work has shown the energy levels are much higher than previously thought.<ref>BBC Science News 7 October 2011 Crab Pulsar's high-energy beam surprises astronomers [https://www.bbc.co.uk/news/science-environment-15203788]</ref> Scientists found emissions at more than 100 GeV (gigaelectronvolts) – 100 [[billion]] times more energetic than visible light.
== Origin ==
The creation of the Crab Nebula corresponds to the bright '''SN 1054''' supernova, which was recorded by Chinese astronomers in 1054 AD. The Crab Nebula itself was first observed in 1731 by John Bevis. The nebula was independently rediscovered in 1758 by [[Charles Messier]] as he was observing a bright [[comet]]. Messier catalogued it as the first entry in his [[Messier Catalogue|catalogue]] of comet-like objects. The [[William Parsons, 3rd Earl of Rosse|Earl of Rosse]] observed the nebula at [[Birr Castle]] in 1848, and referred to the object as the Crab Nebula because a drawing he made of it looked like a crab.<ref>
{{cite journal|author=Glyn Jones, K.|year=1976|title=The search for the nebulae|journal=Journal of the History of Astronomy|volume=7 |pages=67|bibcode=1976JHA.....7...67B}}</ref><ref>{{cite web|last=Rossi|first=B.B.|title=The Crab Nebula ancient history and recent discoveries|url=http://ntrs.nasa.gov/search.jsp?R=19700008151|work=NASA|publisher=NTRS|accessdate=October 1, 1969}}</ref>
[[File:The Crab Nebula NASA.ogv|thumb|left|thumbtime=6|The Crab Nebula video by [[NASA]]]]
In the early 20th century, the analysis of early photographs of the nebula taken several years apart revealed that it was expanding. Tracing the expansion back revealed that the nebula must have become visible on Earth about 900 years ago. Historical records revealed that a new star bright enough to be seen in the daytime had been recorded in the same part of the sky by Chinese astronomers in 1054.<ref name="Mayall">
{{cite journal
|author=Mayall N.U.
|year=1939
|title=The Crab Nebula, a probable supernova
|journal=Astronomical Society of the Pacific Leaflets
|volume=3 |pages=145
|bibcode=1939ASPL....3..145M
|doi=
}}</ref><ref name="Lundmark">
{{cite journal
|author=Lundmark, K.
|year=1921
|title=Suspected new stars recorded in old chronicles and among recent Meridian observations
|journal=Publications of the Astronomical Society of the Pacific
|volume=33 |pages=225
|bibcode=1921PASP...33..225L
|doi=10.1086/123101
}}</ref> Given its great distance, the daytime 'guest star' observed by the Chinese could only have been a [[supernova]]—a massive, exploding star, having exhausted its supply of energy from [[nuclear fusion]] and collapsed in on itself.
Recent analysis of historical records have found that the supernova that created the Crab Nebula probably appeared in April or early May, rising to its maximum brightness of between [[apparent magnitude]] −7 and −4.5 (brighter than everything in the night sky except the [[Moon]]) by July. The supernova was visible to the [[naked eye]] for about two years after its first observation.<ref name="Collinsetal1999">
{{cite journal
| last1 = Collins | first1 = George W., II
| last2 = Claspy | first2 = William P.
| last3 = Martin | first3 = John C.
| year = 1999
| title = A reinterpretation of historical references to the supernova of A.D. 1054
| journal = Publications of the Astronomical Society of the Pacific
| volume = 111 | issue = 761 | pages = 871–880
| bibcode = 1999PASP..111..871C
| doi = 10.1086/316401
|arxiv = astro-ph/9904285 }}</ref> Thanks to the recorded observations of Far Eastern and Middle Eastern astronomers of 1054, Crab Nebula became the first astronomical object recognized as being connected to a supernova explosion.<ref name="Mayall"/>
== References ==
{{Reflist}}
[[Category:Nebulae]]
[[Category:Supernovae]]