Beta Librae

Beta Librae (β Librae, abbreviated Beta Lib, β Lib), formally named Zubeneschamali Template:IPAc-en,<ref name=Kunitzsch>Template:Cite book</ref><ref name="IAU-CSN">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is (despite its 'beta' designation) the brightest star in the zodiac constellation of Libra. From parallax measurements, its distance can be estimated as Template:Convert from the Sun.<ref name=aaa474_2_653/>

The apparent visual magnitude of this star is 2.6.<ref name=scfs/> According to Eratosthenes, Beta Librae was observed to be brighter than Antares. Ptolemy, 350 years later, said it was as bright as Antares. The discrepancy may be due to Antares becoming brighter, but this is not known for certain. It could simply be caused by Beta Librae being a variable star, showing a present-day variability of 0.03 of a magnitude.<ref name="Auk"/>

Name

β Librae (Latinised to Beta Librae) is the star's Bayer designation.

It bore the traditional name Zubeneschamali Template:IPAc-en (less common renderings, or corruptions, are Zuben Eschamali, Zuben el Chamali, Zubenesch, Zubenelg), derived from the Arabic الزُّبَانَى الشَمَالِي (al-zubānā al-šamāliyy) meaning "the northern claw". This name originated in a time when Libra was viewed as representing the "claws of the scorpion".<ref name="Auk"/> There was also Kiffa Borealis, from the Arabic al-kiffah aš-šamāliyy "the northern pan (of the scales)" and the Latin equivalent Lanx Borealis.<ref name=lahire1727/> In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)<ref name="WGSN">Template:Citation</ref> to catalogue and standardize proper names for stars. The WGSN approved the name Zubeneschamali for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN"/>

In Chinese, {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}), meaning Root, refers to an asterism consisting of β Librae, α² Librae, ι Librae and γ Librae.<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 β Librae itself is {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}), "the Fourth Star of Root".<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>

Properties

Based upon the features of its spectrum, Beta Librae has a stellar classification of B8 V,<ref name=apj736_2_89/> making it a B-type main-sequence star. It is about 130 times more luminous than the Sun and has a surface temperature of Template:Val,<ref name=aaa501_1_297/> double that of the Sun. This high temperature produces light with a simple spectrum, making it ideal for examining the interstellar gas and dust between Earth and the star. Like many stars of its kind, it is spinning rapidly, over 100 times faster than the Sun with a projected rotational velocity of Template:Nowrap.<ref name=apj573_1_359/> The measured angular diameter of the primary star is 0.801 mas.<ref name=aaa501_1_297/> At the estimated distance of this system, this yields a physical size of about 4.9 times the radius of the Sun.<ref name=lang2006/>

This type of massive, hydrogen-fusing star often appears blue-white, and is usually stated to be white or bluish by modern observers, but earlier observers often described Beta Librae as the only greenish star visible to the naked eye.<ref name="uiuc"/> There seems to be no generally accepted explanation for why some observers see it as green.<ref name=burnham1978/> The small periodic variations in the magnitude of Beta Librae suggest the presence of a companion star which is not directly observable from Earth.<ref name="glyphweb"/> However, it is categorized as a single star.<ref name=mnras389_2_869/>

In around 200 million years, Beta Librae would have exhausted the supply of hydrogen in its core and become a giant star similar to Beta Herculis, which had a similar initial mass.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

See also

• List of stars in Libra
• Alpha Librae (Zubenelgenubi)

References

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External links

• Template:Citation – Find more Arabic Star Names and their meanings.
• Template:WikiSky