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Alioth
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<h2 id="physical-characteristics">Physical characteristics</h2> <p>According to <i><a href="/facts/Hipparcos/Th2HW7VN">Hipparcos</a></i>, Epsilon Ursae Majoris is 81 <a href="/facts/Light-year/IGc5NdQb">light-years</a> (25 <a href="/facts/Parsec/SwSsk57J">parsecs</a>) from the <a href="/facts/Sun/CadPCVHh">Sun</a>. Its <a href="/facts/Spectral_type/dYrIuK9H">spectral type</a> is <a href="/facts/Ap_and_Bp_stars/S87CqAJV">A1p</a>; the "p" stands for <i><a href="/facts/Peculiar_star/pK0obeCV">peculiar</a></i>, as its <a href="/facts/Stellar_spectrum/NDGQ7mmM">spectrum</a> is characteristic of an <a href="/facts/Alpha2_Canum_Venaticorum_variable/VpU8der6">α2 Canum Venaticorum variable</a>. Epsilon Ursae Majoris, as a representative of this type, may harbor two interacting processes: first, the star's strong <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a> separating different elements in its <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a> 'fuel'; second, a rotation axis at an angle to the magnetic axis may be spinning different bands of magnetically sorted elements into the line of sight between Epsilon Ursae Majoris and the Earth. The intervening elements react differently at different frequencies of light as they whip in and out of view, causing Epsilon Ursae Majoris to have very strange <a href="/facts/Spectral_line/HuI4Bj5f">spectral lines</a> that fluctuate over a period of 5.1 days. The <i>kB9</i> suffix to the spectral type indicates that the <a href="/facts/Calcium/hf252CC0">calcium</a> K line is present and representative of a B9 spectral type even though the rest of the spectrum indicates A1. </p><p>Epsilon Ursae Majoris's rotational and magnetic poles are at almost 90 degrees to one another. Darker (denser) regions of <a href="/facts/Chromium/6sVk6Uu7">chromium</a> form a band at right angles to the equator. </p><p>It has long been suspected that Epsilon Ursae Majoris is a <a href="/facts/Spectroscopic_binary/TYlDe1bD">spectroscopic binary</a>, possibly with more than one companion.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> A more recent study suggests Epsilon Ursae Majoris's 5.1-day variation may be due to a substellar object of about 14.7 <a href="/facts/Jupiter_masses/EtLUmeEN">Jupiter masses</a> in an eccentric orbit (e=0.5) with an average separation of 0.055 <a href="/facts/Astronomical_unit/gjsbu5xU">astronomical units</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> It is now thought that the 5.1-day period is the rotation period of the star, and no companions have been detected using the most modern equipment.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> Observations of Alioth with the <a href="/facts/Navy_Precision_Optical_Interferometer/3WWkA8ef">Navy Precision Optical Interferometer</a> also did not detect a companion.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>Epsilon Ursae Majoris has a relatively weak magnetic field for a variable of this type, 15 times weaker than <a href="/facts/%25CE%2591_Canum_Venaticorum/pI4X6akf">α Canum Venaticorum</a>, but it is still 100 times stronger than <a href="/facts/Earth%2527s_magnetic_field/73G36wmx">that of the Earth</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="name-and-etymology">Name and etymology</h2> <p><i>ε Ursae Majoris</i> (<a href="/facts/Latinisation_of_names/69CA5FuQ">Latinised</a> to <i>Epsilon Ursae Majoris</i>) is the star's <a href="/facts/Bayer_designation/KU2DVT47">Bayer designation</a>. </p><p>The traditional name <i>Alioth</i> comes from the <a href="/facts/Arabic/A1e66hVV">Arabic</a> <i>alyat al-hamal</i> ("the sheep's fat tail"). In 2016, the <a href="/facts/International_Astronomical_Union/GMFPImXo">International Astronomical Union</a> organized a <a href="/facts/Working_Group_on_Star_Names/EoRy108k">Working Group on Star Names</a> (WGSN)<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> included a table of the first two batches of names approved by the WGSN; which included <i>Alioth</i> for this star. </p><p>This star was known to the <a href="/facts/Hindu/D7TFhcg1">Hindus</a> as <i><a href="/facts/Angiras_(sage)/BhmXwYmz">Añgiras</a></i>, one of the <a href="/facts/Saptarishi/tXkbVhRK">Seven Rishis</a>.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p><p>In <a href="/facts/Chinese_astronomy/o84DLtYR">Chinese</a>, 北斗 (<i>Běi Dǒu</i>), meaning <i><a href="/facts/Purple_Forbidden_enclosure/f6M2H80G">Northern Dipper</a></i>, refers to an <a href="/facts/Asterism_(astronomy)/CFu0Qllg">asterism</a> equivalent to the Big Dipper. Consequently, the <a href="/facts/Chinese_star_names/Veh1vExa">Chinese name</a> for Epsilon Ursae Majoris itself is 北斗五 (<i>Běi Dǒu wu</i>, English: the Fifth Star of Northern Dipper) and 玉衡 (<i>Yù Héng</i>, English: Star of Jade Sighting-Tube).<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="namesakes">Namesakes</h2> <p>The <a href="/facts/United_States_Navy/xYK0fUou">United States Navy</a>'s <a href="/facts/Crater_class_cargo_ship/njwUH6k3">Crater class cargo ship</a> <a href="/facts/USS_Allioth/opHc3NNz">USS <i>Allioth</i> (AK-109)</a> was named after the star. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/List_of_brightest_stars/0vDnLEYM">List of brightest stars</a></li> <li><a href="/facts/List_of_nearest_bright_stars/CHHePdRq">List of nearest bright stars</a></li> <li><a href="/facts/Lists_of_stars/4tfAFG9m">Lists of stars</a></li> <li><a href="/facts/Historical_brightest_stars/59KsexKU">Historical brightest stars</a></li></ul> <ol><li>^ This article incorporates text from a publication now in the <a href="/facts/Public_domain/YWKMDKw4">public domain</a>: <a href="/facts/Ephraim_Chambers/Jw3pGdyb">Chambers, Ephraim</a>, ed. (1728). "Allioth". <i><a href="/facts/Cyclop%25C3%25A6dia%2c_or_an_Universal_Dictionary_of_Arts_and_Sciences/RUFoBtqc">Cyclopædia, or an Universal Dictionary of Arts and Sciences</a></i> (1st ed.). James and John Knapton, et al.</li></ol> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7. <a href="978-1-931559-44-7" target="_blank">978-1-931559-44-7</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"IAU Catalog of Star Names". Retrieved 28 July 2016. <a href="http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt" target="_blank">http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Morgan, B. L.; Beddoes, D. R.; Scaddan, R. J.; Dainty, J. C. (1978). "Observations of binary stars by speckle interferometry – I". Monthly Notices of the Royal Astronomical Society. 183 (4): 701–710. Bibcode:1978MNRAS.183..701M. doi:10.1093/mnras/183.4.701. <a href="https://doi.org/10.1093%2Fmnras%2F183.4.701" target="_blank">https://doi.org/10.1093%2Fmnras%2F183.4.701</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Sokolov, N. A. (March 2008), "Radial velocity study of the chemically peculiar star ɛ Ursae Majoris", Monthly Notices of the Royal Astronomical Society: Letters, 385 (1): L1 – L4, arXiv:0904.3562, Bibcode:2008MNRAS.385L...1S, doi:10.1111/j.1745-3933.2008.00419.x, S2CID 17104356. <a href="/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society:_Letters" target="_blank">/wiki/Monthly_Notices_of_the_Royal_Astronomical_Society:_Letters</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Shulyak, D.; Paladini, C.; Causi, G. Li; Perraut, K.; Kochukhov, O. (2014). "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities". Monthly Notices of the Royal Astronomical Society. 443 (2): 1629. arXiv:1406.6093. Bibcode:2014MNRAS.443.1629S. doi:10.1093/mnras/stu1259. S2CID 96452769. <a href="https://doi.org/10.1093%2Fmnras%2Fstu1259" target="_blank">https://doi.org/10.1093%2Fmnras%2Fstu1259</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Baines, Ellyn K.; Clark, James H., III; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023-12-01). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be. ISSN 0004-6256.{{cite journal}}: CS1 maint: multiple names: authors list (link) <a href="https://doi.org/10.3847%2F1538-3881%2Fad08be" target="_blank">https://doi.org/10.3847%2F1538-3881%2Fad08be</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Kochukhov, O.; Shultz, M.; Neiner, C. (2019). "Magnetic field topologies of the bright, weak-field Ap stars θ Aurigae and ∊ Ursae Majoris". Astronomy and Astrophysics. 621: A47. arXiv:1811.04928. Bibcode:2019A&A...621A..47K. doi:10.1051/0004-6361/201834279. S2CID 119070948. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. <a href="https://www.iau.org/science/scientific_bodies/working_groups/280/" target="_blank">https://www.iau.org/science/scientific_bodies/working_groups/280/</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved 28 July 2016. <a href="http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf" target="_blank">http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 438. ISBN 0-486-21079-0. Retrieved 2012-09-04. {{cite book}}: ISBN / Date incompatibility (help) <a href="0-486-21079-0" target="_blank">0-486-21079-0</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>(in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日 Archived 2014-11-02 at the Wayback Machine <a href="http://aeea.nmns.edu.tw/2006/0606/ap060615.html" target="_blank">http://aeea.nmns.edu.tw/2006/0606/ap060615.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> </ol>