Alpha Comae Berenices
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Alpha Comae Berenices (α Comae Berenices, abbreviated Alpha Com, α Com) is a binary star in the northern 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.
Nomenclature
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 has the proper name Diadem, of unknown modern origin.<ref name=kaler/> 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>
Properties
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. If eclipses do occur, the next primary eclipse is expected to be around 27 September 2040; the next date for a secondary eclipse, which has only a 3.3% probability of happening, is 11 January 2026.<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.