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Created page with "{{Night Sky | image = | designation =Adhara<br/>21 Canis Majoris | rightascension =07<sup>h</sup> 25<sup>m</sup> 38.8983<sup>s</sup><ref name=simbad>{{cite web|..."
{{Night Sky
| image =
| designation =Adhara<br/>21 Canis Majoris
| rightascension =07<sup>h</sup> 25<sup>m</sup> 38.8983<sup>s</sup><ref name=simbad>{{cite web|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Epsilon+Canis+Minoris&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id|title=Epsilon Canis Minoris|accessdate=June 27, 2020|work=Simbad Astronomical Database|publisher=simbad.u-strasbg.fr}}</ref><ref name=Gaia>{{cite journal
|last1=Gaia Collaboration |first1=
|title=VizieR Online Data Catalog: Gaia DR2
|journal=VizieR Online Data Catalog
|volume=I/345
|issue=|page=I/345|date=2018
|doi=
|bibcode=2018yCat.1345....0G
|ref=harv
}} {{arXiv|0708.1752}}</ref>
| declination =+09° 16′ 33.9268″<ref name=simbad/><ref name=Gaia/>
| distance =405.17 ly<ref name=universeguide>{{cite web|url=https://www.universeguide.com/star/33579/adhara|title=Adhara (Epsilon Canis Majoris, 21 Canis Majoris) Star Facts|accessdate=June 27, 2020|publisher=universeguide.com}}</ref>
| constellation =Canis Major
| type =Bright giant star
| dimensions =
| magnitude =Apparent Mag: +1.50<ref name=universeguide/><br/>Absolute Mag: -4.10 / -3.97<ref name=universeguide/>
| redshift =
| radvelocity =-6.90 ± 0.20 km/s<ref name=simbad/><ref name=Gaia/>
| propmotion =RA: -3.338 mas/yr<ref name=simbad/><ref name=Gaia/><br/>Dec: -8.497 mas/yr<ref name=simbad/><ref name=Gaia/>
| parallax =4.2624 ± 0.2288 mas<ref name=simbad/><ref name=Gaia/>
}}
Epsilon Canis Majoris (Adhara, 21 Canis Majoris) is a [[bright giant star]] and, unusually for its [[Bayer designation]] of epsilon, is the second brightest in the [[constellation]] of [[Canis Major]].<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/adhara.html|title=Adhara|accessdate=June 27, 2020|publisher=stars.asto.illinois.edu|author=Jim Kaller|work=STARS|date=June 6, 2009}}</ref> The 22<sup>nd</sup> most luminous star in the sky, it can easily be observed with the unaided eye and is most easily seen in February. This means along with other stars such as [[Sirius]], it is often used for [[celestial navigation]]. The star is in fact a [[binary star|binary system]] where the larger primary star is designated "Epsilon Canis Majoris A" and the smaller secondary "Epsilon Canis Majoris B". Epsilon Canis Majoris A is known for being the brightest source of [[ultraviolet]] radiation known.<ref name=newscientist>{{cite web|url=https://www.newscientist.com/article/mg14519643-000-electrifying-touch-of-a-distant-star/|title=Electrifying touch of a distant star|accessdate=June 27, 2020|publisher=newscientist.com|author=Ken Croswell|date=February 11, 1995}}</ref>
Adhara's name comes from the [[Arabic]] "aðāra" or "Al Adhara" where it translates as "maidens".<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/constellation-list/canis-major-constellation/|title=Canis Major Constellation|accessdate=June 27, 2020|publisher=constellation-guide.com}}</ref>
It is not known who first called the star by this name, though the [[Eqypt|Egyptian]] astronomer Al Achsasi al Mouakket refered to it as "Aoul al Adzari".<ref name=star-facts>{{cite web|url=https://www.star-facts.com/adhara/|title=ADHARA|accessdate=June 27, 2020|publisher=star=facts.com|date=September 25, 2019}}</ref> Sometimes the star is spelled slightly differently, various spellings include: Udra, Udara, Adard and Adara. The star is also known in [[Chinese]] as 弧矢七 (Hú Shǐ qī, Seventh Star of Bow and Arrow), where is is part of a Chinese [[asterism]] called the "Bow and Arrow". It is one of the 23 stars on the national flag of [[Brazil]], where it represents the Brazzilian state of Tocantins.
==Properties and structure==
The Epsilon Canis Majoris system can be found 405.17 [[light year]]s from [[Earth]].<ref name=star-facts/> The larger Epsilon Canis Majoris A is thought to have a [[mass]] of 12.6 [[solar mass]]es and radius 13.9 times larger than the [[Sun]]'s. It possesses an apparent magnitude of +1.50 and a [[spectral class]] of B2. The star is though to rotate with an equitorial speed of 38 km/s.<ref name=illinois/> With a surface temperature of 21,900 kelvin, the star appears blue-white and is extremly luminous; it emits roughly 20,000 times more energy per second than the Sun.<ref name=space.com>{{cite web|url=https://www.space.com/22980-adhara.html|title=Adhara: Brightest Star in Ultraviolet Light|accessdate=June 27, 2020|publisher=space.com|author=Elizabeth Howell|date=Septermbe 27, 2013}}</ref><ref name=astropixels>{{cite web|url=http://astropixels.com/stars/Adhara-01.html|title=Adhara|accessdate=June 27, 2020|publisher=astropixels.comdate=January 31, 2012}}</ref> The high temperature leads to large amouts of radiation emitted in the [[ultraviolet]] portion of the star's [[spectrum]]; it is 38.700 times brighter than the Sun here.<ref name=nineplanets>{{cite web|url=https://nineplanets.org/adhara-%CE%B5-canis-majoris/|title=Adhara (ε Canis Majoris) Facts|accessdate=June 27, 2020|publisher=nineplanets.org|date=January 30, 2020}}</ref> In fact is is known as an extreme ultraviolet source and was discovered by the Extreme Ultraviolet Explorer (EUVE) all-sky survey to be brighter than any other star in UV light, but as UV can't be seen by humans, it drops down to the 22<sup>nd</sup> brightest star in the night sky. The UV light is able [[ionization|ionize]] [[hydrogen]] [[atom]]s and [[molecule]]s close to the star.<ref>{{cite web|url=https://ntrs.nasa.gov/search.jsp?R=19950064064|title=NASA Technical Reports Server (NTRS) - Epsilon Canis Majoris and the ionization of the local cloud|accessdate=June 27, 2020|publisher=ntrs.nasa.gov|work=Epsilon Canis Majoris and the ionization of the local cloud|date=May 10, 1995}}</ref> The star is used to determine the ionization state of the Local Interstellar Cloud as it is the strongest UV source near us.<ref name=nineplanets/> The cloud is 30 ly across and our own [[Solar System]] is contained within it.
Less is known about the companion Epsilon Canis Majoris B. It is perhaps 250 times fainter than Epsilon Canis Majoris at a magnitude of +7.50, though some sources place it fainter still at +8 or even +9.<ref name=space.com/><ref name=illinois/> It is thought to have an [[absolute magnitude]] of +1.9.<ref name=star-facts/> Epsilon Canis Majoris B is hard to observe except with a large [[telescope]] as it is located only around 900 [[Astronomical Units]] or 7.5 [[arcsecond]]s away from Epsilon Canis Majoris A and Epsilon Canis Majoris A is so much brighter.<ref>{{cite web|url=https://www.daviddarling.info/encyclopedia/A/Adhara.html|title=Adhara (Epsilon Canis Majoris)|accessdate=June 27, 2020|publisher=daviddarling.info}}</ref>
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Stars]]
| image =
| designation =Adhara<br/>21 Canis Majoris
| rightascension =07<sup>h</sup> 25<sup>m</sup> 38.8983<sup>s</sup><ref name=simbad>{{cite web|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Epsilon+Canis+Minoris&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id|title=Epsilon Canis Minoris|accessdate=June 27, 2020|work=Simbad Astronomical Database|publisher=simbad.u-strasbg.fr}}</ref><ref name=Gaia>{{cite journal
|last1=Gaia Collaboration |first1=
|title=VizieR Online Data Catalog: Gaia DR2
|journal=VizieR Online Data Catalog
|volume=I/345
|issue=|page=I/345|date=2018
|doi=
|bibcode=2018yCat.1345....0G
|ref=harv
}} {{arXiv|0708.1752}}</ref>
| declination =+09° 16′ 33.9268″<ref name=simbad/><ref name=Gaia/>
| distance =405.17 ly<ref name=universeguide>{{cite web|url=https://www.universeguide.com/star/33579/adhara|title=Adhara (Epsilon Canis Majoris, 21 Canis Majoris) Star Facts|accessdate=June 27, 2020|publisher=universeguide.com}}</ref>
| constellation =Canis Major
| type =Bright giant star
| dimensions =
| magnitude =Apparent Mag: +1.50<ref name=universeguide/><br/>Absolute Mag: -4.10 / -3.97<ref name=universeguide/>
| redshift =
| radvelocity =-6.90 ± 0.20 km/s<ref name=simbad/><ref name=Gaia/>
| propmotion =RA: -3.338 mas/yr<ref name=simbad/><ref name=Gaia/><br/>Dec: -8.497 mas/yr<ref name=simbad/><ref name=Gaia/>
| parallax =4.2624 ± 0.2288 mas<ref name=simbad/><ref name=Gaia/>
}}
Epsilon Canis Majoris (Adhara, 21 Canis Majoris) is a [[bright giant star]] and, unusually for its [[Bayer designation]] of epsilon, is the second brightest in the [[constellation]] of [[Canis Major]].<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/adhara.html|title=Adhara|accessdate=June 27, 2020|publisher=stars.asto.illinois.edu|author=Jim Kaller|work=STARS|date=June 6, 2009}}</ref> The 22<sup>nd</sup> most luminous star in the sky, it can easily be observed with the unaided eye and is most easily seen in February. This means along with other stars such as [[Sirius]], it is often used for [[celestial navigation]]. The star is in fact a [[binary star|binary system]] where the larger primary star is designated "Epsilon Canis Majoris A" and the smaller secondary "Epsilon Canis Majoris B". Epsilon Canis Majoris A is known for being the brightest source of [[ultraviolet]] radiation known.<ref name=newscientist>{{cite web|url=https://www.newscientist.com/article/mg14519643-000-electrifying-touch-of-a-distant-star/|title=Electrifying touch of a distant star|accessdate=June 27, 2020|publisher=newscientist.com|author=Ken Croswell|date=February 11, 1995}}</ref>
Adhara's name comes from the [[Arabic]] "aðāra" or "Al Adhara" where it translates as "maidens".<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/constellation-list/canis-major-constellation/|title=Canis Major Constellation|accessdate=June 27, 2020|publisher=constellation-guide.com}}</ref>
It is not known who first called the star by this name, though the [[Eqypt|Egyptian]] astronomer Al Achsasi al Mouakket refered to it as "Aoul al Adzari".<ref name=star-facts>{{cite web|url=https://www.star-facts.com/adhara/|title=ADHARA|accessdate=June 27, 2020|publisher=star=facts.com|date=September 25, 2019}}</ref> Sometimes the star is spelled slightly differently, various spellings include: Udra, Udara, Adard and Adara. The star is also known in [[Chinese]] as 弧矢七 (Hú Shǐ qī, Seventh Star of Bow and Arrow), where is is part of a Chinese [[asterism]] called the "Bow and Arrow". It is one of the 23 stars on the national flag of [[Brazil]], where it represents the Brazzilian state of Tocantins.
==Properties and structure==
The Epsilon Canis Majoris system can be found 405.17 [[light year]]s from [[Earth]].<ref name=star-facts/> The larger Epsilon Canis Majoris A is thought to have a [[mass]] of 12.6 [[solar mass]]es and radius 13.9 times larger than the [[Sun]]'s. It possesses an apparent magnitude of +1.50 and a [[spectral class]] of B2. The star is though to rotate with an equitorial speed of 38 km/s.<ref name=illinois/> With a surface temperature of 21,900 kelvin, the star appears blue-white and is extremly luminous; it emits roughly 20,000 times more energy per second than the Sun.<ref name=space.com>{{cite web|url=https://www.space.com/22980-adhara.html|title=Adhara: Brightest Star in Ultraviolet Light|accessdate=June 27, 2020|publisher=space.com|author=Elizabeth Howell|date=Septermbe 27, 2013}}</ref><ref name=astropixels>{{cite web|url=http://astropixels.com/stars/Adhara-01.html|title=Adhara|accessdate=June 27, 2020|publisher=astropixels.comdate=January 31, 2012}}</ref> The high temperature leads to large amouts of radiation emitted in the [[ultraviolet]] portion of the star's [[spectrum]]; it is 38.700 times brighter than the Sun here.<ref name=nineplanets>{{cite web|url=https://nineplanets.org/adhara-%CE%B5-canis-majoris/|title=Adhara (ε Canis Majoris) Facts|accessdate=June 27, 2020|publisher=nineplanets.org|date=January 30, 2020}}</ref> In fact is is known as an extreme ultraviolet source and was discovered by the Extreme Ultraviolet Explorer (EUVE) all-sky survey to be brighter than any other star in UV light, but as UV can't be seen by humans, it drops down to the 22<sup>nd</sup> brightest star in the night sky. The UV light is able [[ionization|ionize]] [[hydrogen]] [[atom]]s and [[molecule]]s close to the star.<ref>{{cite web|url=https://ntrs.nasa.gov/search.jsp?R=19950064064|title=NASA Technical Reports Server (NTRS) - Epsilon Canis Majoris and the ionization of the local cloud|accessdate=June 27, 2020|publisher=ntrs.nasa.gov|work=Epsilon Canis Majoris and the ionization of the local cloud|date=May 10, 1995}}</ref> The star is used to determine the ionization state of the Local Interstellar Cloud as it is the strongest UV source near us.<ref name=nineplanets/> The cloud is 30 ly across and our own [[Solar System]] is contained within it.
Less is known about the companion Epsilon Canis Majoris B. It is perhaps 250 times fainter than Epsilon Canis Majoris at a magnitude of +7.50, though some sources place it fainter still at +8 or even +9.<ref name=space.com/><ref name=illinois/> It is thought to have an [[absolute magnitude]] of +1.9.<ref name=star-facts/> Epsilon Canis Majoris B is hard to observe except with a large [[telescope]] as it is located only around 900 [[Astronomical Units]] or 7.5 [[arcsecond]]s away from Epsilon Canis Majoris A and Epsilon Canis Majoris A is so much brighter.<ref>{{cite web|url=https://www.daviddarling.info/encyclopedia/A/Adhara.html|title=Adhara (Epsilon Canis Majoris)|accessdate=June 27, 2020|publisher=daviddarling.info}}</ref>
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Stars]]