Eta Canis Majoris
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Eta Canis Majoris (η Canis Majoris, abbreviated Eta CMa, η CMa), also named Aludra Template:IPAc-en,<ref name="IAU-CSN">Template:Cite web</ref> is a star in the constellation of Canis Major. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.<ref name=baas25_1319/>
Nomenclature
[edit]η Canis Majoris (Latinised to Eta Canis Majoris) is the star's Bayer designation.
The traditional name Aludra originates from the Arabic: العذراء al-adhraa, 'the virgin'. This star, along with Epsilon Canis Majoris (Adhara), Delta Canis Majoris (Wezen) and Omicron2 Canis Majoris (Thanih al Adzari), were Al 'Adhārā (العذاري), 'the Virgins'.<ref name=allen1963/> In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1"/> included a table of the first two batches of names approved by the WGSN; which included Aludra for this star.
In Chinese, Template:Lang (Template:Lang), meaning Bow and Arrow,<ref name=KooShe/> refers to an asterism consisting of Eta Canis Majoris, Delta Canis Majoris, HD 63032, HD 65456, Omicron Puppis, k Puppis, Epsilon Canis Majoris, Kappa Canis Majoris and Pi Puppis. Consequently, Eta Canis Majoris itself is known as Template:Lang (Template:Lang, Template:Langx).<ref name=AEEA/>
Properties
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Eta Canis Majoris is a blue supergiant with a spectral type B5Ia. It has been the standard for this spectral class in the Morgan–Keenan system.<ref name=morgan1978/> It is likely a post-red supergiant, a star which left its red supergiant phase and near the end of its life. As a consequence, Eta CMa has lost significant part of its mass, and now has a mass of either Template:Solar mass, depending on the estimate, in contrast with its initial mass of Template:Solar mass.<ref name=Sanchez2023/>
Eta CMa shines brightly in the skies in spite of a large distance from Earth due to being intrinsically many times brighter than the Sun. It has a luminosity over 100,000 times and a radius around 54 times that of the Sun. It has only existed for a fraction of the time the Sun has, less than 10 million years, yet is already in the last stages of its life.<ref name=haucke2018/><ref name=Sanchez2023/>
Eta CMa is classified as an Alpha Cygni-type variable star and its brightness varies from magnitude +2.38 to +2.48 over a period of 4.7 days.<ref name=Kazarovets/><ref name=AAVSOeta/>
Namesakes
[edit]Both USS Aludra (AF-55), an Alstede-class stores ship, and USS Aludra (AK-72), a Crater-class cargo ship, were U.S. Navy vessels named after the star.