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Created page with "{{Night Sky | image = | designation =Cas A | rightascension =23<sup>h</sup> 23<sup>m</sup> 26<sup>s</sup><ref name=constellation-guide>[http://www.constellation..."
{{Night Sky
| image =
| designation =Cas A
| rightascension =23<sup>h</sup> 23<sup>m</sup> 26<sup>s</sup><ref name=constellation-guide>[http://www.constellation-guide.com/cassiopeia-a/ Cassiopeia A] from constellation-guide.com</ref>
| declination =+58° 48′<ref name=constellation-guide/>
| distance =11,000 ly<ref name=constellation-guide/>
| constellation =Cassiopeia
| type =supernova{{!}}Supernova remnant
| dimensions =3 arcminutes<ref name=constellation-guide/>
| magnitude =
| redshift =
| radvelocity =
| propmotion =
| parallax =
}}
'''Cassiopeia A''' (Cas A) is a [[supernova]] remnant in the [[constellation]] of [[Cassiopeia]].<ref name=constellation-guide/> The supernova that caused it is thought to have occurred around 300 years ago, though no definite recording of a supernova was made at that time. One possibility of it may have been made by John Flamsteed on August 16, 1680. Flamsteed observed a [[star]] with an [[star magnitude|apparent magnitude]] of +6 near the nebula but Flamsteed's position for the star does not correspond to any known star today.<ref name=constellation-guide/> The nebula also houses a [[radio waves|radio]] source, designated Cas A and first observed in 1947.<ref name=constellation-guide/> For [[frequency|frequencies]] above 1 GHz, Cassiopeia A is the brightest radio source in the night sky.
==Properties and Structure==
At around 11,000 [[light year]]s away, the nebula's apparent size of 5 arcminutes corresponds to a physical diameter of around 10 light years.<ref name=constellation-guide/> The nebula's outer shell is expanding at roughly 4,000-6,000 km/s and is believed to have a temperature of 27.7 million Kelvin.<ref name=constellation-guide/> The expansion rate suggests it cannot be more than a couple of hundred years old, though no record of a supernova exists at that time. This may be because the star ejected most of its outer layers or perhaps it was hidden behind a cloud of interstellar gas and dust.
At the centre of the nebula is a [[neutron star]]. It was the first neutron star to observed to possess an atmosphere containing [[carbon]].<ref name=britannica>[https://www.britannica.com/place/Cassiopeia-A Cassiopeia A] from britannica.com</ref> The star is also cooling very quickly, decreasing by 4% over the ten years it has been observed by the [[Chandra Space Telescope]].<ref>[http://chandra.harvard.edu/photo/2011/casa/ Cassiopeia A: NASA'S Chandra Finds Superfluid in Neutron Star's Core] from chandra.harvard.edu</ref> It is believed this indicates the core of the star is a superfluid. In 2013 the element [[phosphorus]] was also detected in the nebula as a whole in concentrations more than 100 times greater than the average for the [[Milky Way]].<ref name=constellation-guide/>
The nebula is a very bright [[radio waves|radio]] source, the most luminous visible from [[Earth]] for [[frequency|frequencies]] above 1 GHz. Below this , the radio source [[Cygnus A]] is brighter.
The nebula has been modelled in 3D and is the only supernova remnant for which this has been done.<ref name=constellation-guide/><ref>[https://www.nasa.gov/mission_pages/chandra/multimedia/exploring-cassiopeiaA.html Exploring the Third Dimension of Cassiopeia A] from nasa.gov</ref> This model was generated using data from [[NASA]]'s Chandra Space Telescope and its [[Spitzer Space Telescope]]. From this it was discovered that there are perhaps 6 or so empty chambers within the nebula. These are large, two of them being 3 and 6 light years across.<ref name=constellation-guide/>
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]
| image =
| designation =Cas A
| rightascension =23<sup>h</sup> 23<sup>m</sup> 26<sup>s</sup><ref name=constellation-guide>[http://www.constellation-guide.com/cassiopeia-a/ Cassiopeia A] from constellation-guide.com</ref>
| declination =+58° 48′<ref name=constellation-guide/>
| distance =11,000 ly<ref name=constellation-guide/>
| constellation =Cassiopeia
| type =supernova{{!}}Supernova remnant
| dimensions =3 arcminutes<ref name=constellation-guide/>
| magnitude =
| redshift =
| radvelocity =
| propmotion =
| parallax =
}}
'''Cassiopeia A''' (Cas A) is a [[supernova]] remnant in the [[constellation]] of [[Cassiopeia]].<ref name=constellation-guide/> The supernova that caused it is thought to have occurred around 300 years ago, though no definite recording of a supernova was made at that time. One possibility of it may have been made by John Flamsteed on August 16, 1680. Flamsteed observed a [[star]] with an [[star magnitude|apparent magnitude]] of +6 near the nebula but Flamsteed's position for the star does not correspond to any known star today.<ref name=constellation-guide/> The nebula also houses a [[radio waves|radio]] source, designated Cas A and first observed in 1947.<ref name=constellation-guide/> For [[frequency|frequencies]] above 1 GHz, Cassiopeia A is the brightest radio source in the night sky.
==Properties and Structure==
At around 11,000 [[light year]]s away, the nebula's apparent size of 5 arcminutes corresponds to a physical diameter of around 10 light years.<ref name=constellation-guide/> The nebula's outer shell is expanding at roughly 4,000-6,000 km/s and is believed to have a temperature of 27.7 million Kelvin.<ref name=constellation-guide/> The expansion rate suggests it cannot be more than a couple of hundred years old, though no record of a supernova exists at that time. This may be because the star ejected most of its outer layers or perhaps it was hidden behind a cloud of interstellar gas and dust.
At the centre of the nebula is a [[neutron star]]. It was the first neutron star to observed to possess an atmosphere containing [[carbon]].<ref name=britannica>[https://www.britannica.com/place/Cassiopeia-A Cassiopeia A] from britannica.com</ref> The star is also cooling very quickly, decreasing by 4% over the ten years it has been observed by the [[Chandra Space Telescope]].<ref>[http://chandra.harvard.edu/photo/2011/casa/ Cassiopeia A: NASA'S Chandra Finds Superfluid in Neutron Star's Core] from chandra.harvard.edu</ref> It is believed this indicates the core of the star is a superfluid. In 2013 the element [[phosphorus]] was also detected in the nebula as a whole in concentrations more than 100 times greater than the average for the [[Milky Way]].<ref name=constellation-guide/>
The nebula is a very bright [[radio waves|radio]] source, the most luminous visible from [[Earth]] for [[frequency|frequencies]] above 1 GHz. Below this , the radio source [[Cygnus A]] is brighter.
The nebula has been modelled in 3D and is the only supernova remnant for which this has been done.<ref name=constellation-guide/><ref>[https://www.nasa.gov/mission_pages/chandra/multimedia/exploring-cassiopeiaA.html Exploring the Third Dimension of Cassiopeia A] from nasa.gov</ref> This model was generated using data from [[NASA]]'s Chandra Space Telescope and its [[Spitzer Space Telescope]]. From this it was discovered that there are perhaps 6 or so empty chambers within the nebula. These are large, two of them being 3 and 6 light years across.<ref name=constellation-guide/>
==References==
{{reflist}}
{{Nebulae}}
[[Category:Astronomy]]
[[Category:Nebulae]]