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Alpha Comae Berenices (α Comae Berenices, abbreviated Alpha Com, α Com) is a binary star in the constellation of Coma Berenices (Berenice's Hair), Template:Convert away. It consists of two main sequence stars, each a little hotter and more luminous than the Sun.

Alpha Comae Berenices is said to represent the crown worn by Queen Berenice. The two components are designated Alpha Comae Berenices A (officially named Diadem Template:IPAc-en, the traditional name for the system)<ref name="IAU-LSN">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and B.

NomenclatureEdit

α Comae Berenices (Latinised to Alpha Comae Berenices) is the system's Bayer designation. The designations of the two components as Alpha Comae Berenices A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).<ref name="planetnaming">Template:Cite arXiv</ref>

The system bore the traditional names Diadem and Al Dafirah, the latter derived from the Arabic الضفيرة ađ̧-đ̧afīrah "the braid".Template:Cn In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.<ref name="TriRpt18">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It approved the name Diadem for the component Alpha Comae Berenices A on 1 February 2017 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>

In Chinese, {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of Alpha Comae Berenices, Eta Virginis, Gamma Virginis, Delta Virginis and Epsilon Virginis.<ref>Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.</ref> Consequently, the Chinese name for Alpha Comae Berenices itself is {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}, Template:Langx.),<ref>Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref> representing {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}), meaning The First Eastern General.<ref>Template:In lang English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref> 東上將 (Dōngshǎngjiāng), westernized into Shang Tseang, but that name was designated for "v Comae Berenices" by R.H. Allen and the meaning is "a Higher General".<ref>Richard Hinckley Allen: Star Names — Their Lore and Meaning: Coma Berenices</ref>

PropertiesEdit

Although Alpha Comae Berenices bears the title "alpha", at magnitude 4.32 it is actually fainter than Beta Comae Berenices.

It is a binary star, with almost equal components of magnitudes 5.05 m and 5.08 m orbiting each other with a period of 25.87 years. The system, estimated to be 58 light-years distant, appears so nearly "edge-on" from the Earth that the two stars appear to move back-and-forth in a straight line with a maximum separation of only 0.7 arcsec. Eclipses are predicted to occur between the two components however they have not been successfully observed due to miscalculations of the time of eclipse.<ref name="Muterspaugh2015"/>

The mean separation between them is approximately 10 AU, about the distance between the Sun and Saturn.

The binary star has a visual companion, CCDM J13100+1732C, of apparent magnitude 10.2, located 89 arcseconds away along a position angle of 345°.<ref name=wds>Entry 13100+1732, discoverer code STF1728, components AB-C, The Washington Double Star Catalog Template:Webarchive, United States Naval Observatory. Accessed on line September 3, 2008.</ref>

Alpha Comae Berenicis forms an isosceles triangle with globular star clusters Messier 53 and NGC 5053. The apparent diameter of this triangle is a little more than one degree. The location of Alpha Comae Berenicis is westward (preceding) of both globular star clusters.

ReferencesEdit

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External linksEdit

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