Beta Arietis

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Beta Arietis is a binary star system in the constellation of Aries, marking the ram's second horn. Its identifier is a Bayer designation that is Latinized from β Arietis, and abbreviated Beta Ari or β Ari. It has the official name Sheratan, pronounced Template:IPAc-en.<ref name=Kunitzsch/><ref name="IAU-CSN"/> This system is visible to the naked eye as a point of light with a combined apparent visual magnitude of 2.65, making this the second-brightest star in the constellation. Located at a distance of Template:Convert, the pair orbit each other with a period of 107 days.

NomenclatureEdit

Beta Arietis is the star's Bayer designation. It also bears the Flamsteed designation 6 Arietis.

The traditional name, Sheratan (or Sharatan, Sheratim),<ref name=allen1899/> in full Al Sharatan, is from the Arabic الشرطان aš-šaraţān "the two signs", a reference to the star having marked the northern vernal equinox together with Gamma Arietis several thousand years ago.Template:Citation needed In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)<ref name="WGSN"/> to catalogue and standardize proper names for stars. The WGSN approved the name Sheratan for this star on August 21, 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 Bond (asterism), refers to an asterism consisting of β Arietis, γ Arietis and α Arietis.<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 Arietis 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>

PropertiesEdit

Beta Arietis has an apparent visual magnitude of 2.65. Based on dynamical parallax measurements, it is located at a distance of Template:Convert from Earth.<ref name=sb2/> This is a spectroscopic binary star system consisting of a pair of stars orbiting around each other with a separation that can not currently be resolved with a conventional telescope. However, the pair have been resolved using the Mark III Stellar Interferometer at the Mount Wilson Observatory. This allows the orbital elements to be computed, as well as the individual masses of the two stars. The stars complete their highly elliptical orbit every 107 days.<ref name=apj356_641/>

The primary star has a stellar classification of A3 V,<ref name=sb2/> which means it is an A-type main-sequence star that is generating energy through the thermonuclear fusion of hydrogen in its core region. The NStars project gives the star a spectral type of kA4 hA5 mA5 Va under the revised MK spectral classification system.<ref name=aj126_4_2048/> The secondary star is a G-type main-sequence star, with a stellar classification of G2V.<ref name=sb2/> It is about four magnitudes fainter than the primary; hence the energy output from the system is dominated by the primary star.<ref name=apj356_641/> In a few million years, as the primary evolves toward a red giant, significant amounts of mass transfer to the secondary component is expected.<ref name=mnras384_1_173/>

The primary has been classified as a rapid rotator, with a projected rotational velocity of 73 km/s providing a lower bound on the azimuthal rotational velocity along the equator.<ref name=aaa463_2_671/> It may also be a mildly Am star, which is a class of stars that show a peculiar spectrum with strong absorption lines from various elements and deficiencies in others. In β Arietis, these absorption lines are broadened because of the Doppler effect from the rotation, making analysis of the abundance patterns difficult.<ref name=aaass27_35/>

This system has been examined with the Spitzer Space Telescope for the presence of an excess emission of infrared, which would indicate a disk of dust. However, no significant excess was detected.<ref name=aj126_4_2048/>

NotesEdit

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ReferencesEdit

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External linksEdit

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