Editing Alioth

{{short description|Star in the constellation Ursa Major}}
{{Other uses}}
{{Starbox begin}}
{{Starbox image
 | image=
   {{Location mark
     | image=Ursa Major constellation map.svg
     | float=center | width=250 | position=right
     | mark=Red circle.svg | mark_width=10 | mark_link=ε UMa
     | x%=28.4 | y%=44.6
   }}
 | caption=Location of Alioth (circled)
}}
{{Starbox observe
 | epoch       = J2000
 | ra          = {{RA|12|54|01.74959}}<ref name=aaa474_2_653/>
 | dec         = {{DEC|+55|57|35.3627}}<ref name=aaa474_2_653/>
 | appmag_v    = 1.77<ref name=clpl4_99/>
 | constell    = [[Ursa Major]]
}}
{{Starbox character
 | class       = A1III-IVp kB9
 | b-v         = −0.02<ref name=clpl4_99/>
 | u-b         = +0.02<ref name=clpl4_99/>
 | variable    = [[Alpha² Canum Venaticorum variable|α<sup>2</sup> CVn]]
}}
{{Starbox astrometry
 | radial_v    = −9.3<ref name=rgcrv/>
 | prop_mo_ra  = +111.91
 | prop_mo_dec = −8.24
 | pm_footnote = <ref name=aaa474_2_653/>
 | parallax    = 39.51
 | p_error     = 0.20
 | parallax_footnote = <ref name=aaa474_2_653/>
 | absmag_v    = −0.2<ref name=aass77_1_41/>
}}
{{Starbox detail
 | mass        = 2.91<ref name=apjss192_1_2/>
 | radius      = {{val|4.29|0.19|0.21}}<ref name="npoi"/>
 | luminosity  = {{val|104.4|9.3}}<ref name="npoi"/>
 | temperature = {{val|8908|24|fmt=commas}}<ref name="npoi"/>
 | gravity     = 3.59<ref name="npoi"/>
 | metal_fe    = +0.00<ref name=aass77_1_41/>
 | rotational_velocity = 33<ref name=aaa393_897/>
 | age_myr     = 300<ref name=nakajima/>
}}
{{Starbox catalog
 | names = {{odlist | name=Alioth, Allioth, Aliath | B=ε UMa | F=77 Ursae Majoris | BD=+56°1627 | FK5=483 | GC=17518 | HD=112185 | HIP=62956 | HR=4905 | PPM=33769 | SAO=28553 }}
}}
{{Starbox reference
| Simbad = ALIOTH
}}
{{Starbox end}}

'''Alioth''' {{IPAc-en|'|æ|l|i|Q|θ|audio=LL-Q1860 (eng)-Naomi Persephone Amethyst (NaomiAmethyst)-Alioth.wav}}, also called '''Epsilon Ursae Majoris''', is a [[star]] in the northern [[constellation]] of [[Ursa Major]]. The designation is [[Latinisation of names|Latinised]] from '''ε&nbsp;Ursae Majoris''' and abbreviated '''Epsilon&nbsp;UMa''' or '''ε&nbsp;UMa'''.<ref name=Kunitzsch>{{cite book
  |last1=Kunitzsch |first1=Paul
  |last2=Smart |first2=Tim
  |date = 2006  |edition = 2nd rev.
  |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
  |publisher = Sky Pub |location = Cambridge, Massachusetts
  |isbn = 978-1-931559-44-7
}}</ref><ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref> Despite being designated "ε"'''&nbsp;'''([[epsilon]]), it is the brightest star in the constellation and at [[apparent magnitude|magnitude]] 1.77 is the [[list of brightest stars|thirty-third brightest star in the sky]].

It is the star in the tail of the bear closest to its body, and thus the star in the handle of the [[Big Dipper]] (or Plough) closest to the bowl. It is also a member of the large and diffuse [[Ursa Major moving group]]. Historically, the star was frequently used in [[celestial navigation]] in the maritime trade, because it is listed as one of the 57 [[navigational stars]].{{ref label|1728|1|^}}

==Physical characteristics==
[[Image:Sidney Hall - Urania's Mirror - Ursa Major.jpg|thumb|200px|left|Book plate by [[Sidney Hall]] depicting Ursa Major's stars]]
[[File:EpsUMaLightCurve.png|thumb|left|A [[light curve]] for Epsilon Ursae Majoris, plotted from ''[[TESS]]'' data<ref name=MAST/>]]

According to ''[[Hipparcos]]'', Epsilon Ursae Majoris is {{convert|81|ly|pc|abbr=off|lk=on}} from the [[Sun]]. Its [[spectral type]] is [[Ap and Bp stars|A1p]]; the "p" stands for ''[[Peculiar star|peculiar]]'', as its [[stellar spectrum|spectrum]] is characteristic of an [[Alpha2 Canum Venaticorum variable|α<sup>2</sup> Canum Venaticorum variable]]. Epsilon Ursae Majoris, as a representative of this type, may harbor two interacting processes: first, the star's strong [[magnetic field]] separating different elements in its [[hydrogen]] '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 [[spectral line]]s that fluctuate over a period of 5.1 days. The ''kB9'' suffix to the spectral type indicates that the [[calcium]] K line is present and representative of a B9 spectral type even though the rest of the spectrum indicates A1.

Epsilon Ursae Majoris's rotational and magnetic poles are at almost 90 degrees to one another. Darker (denser) regions of [[chromium]] form a band at right angles to the equator.

It has long been suspected that Epsilon Ursae Majoris is a [[spectroscopic binary]], possibly with more than one companion.<ref name=morgan/>  A more recent study suggests Epsilon Ursae Majoris's 5.1-day variation may be due to a substellar object of about 14.7 [[Jupiter masses]] in an eccentric orbit (e=0.5) with an average separation of 0.055 [[astronomical unit]]s.<ref name="MNRASL385_1_L1"/>  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.<ref name=shulyak/> Observations of Alioth with the [[Navy Precision Optical Interferometer]] also did not detect a companion.<ref name="npoi"/>

Epsilon Ursae Majoris has a relatively weak magnetic field for a variable of this type, 15 times weaker than [[α Canum Venaticorum]], but it is still 100 times stronger than [[Earth's magnetic field|that of the Earth]].<ref name=weakfield/>

==Name and etymology==

''ε&nbsp;Ursae Majoris'' ([[Latinisation of names|Latinised]] to ''Epsilon Ursae Majoris'') is the star's [[Bayer designation]].

The traditional name ''Alioth'' comes from the [[Arabic]] ''alyat al-hamal'' ("the sheep's fat tail"). In 2016, the [[International Astronomical Union]] organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf |archive-date=2022-10-09 |url-status=live | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> included a table of the first two batches of names approved by the WGSN; which included ''Alioth'' for this star.

This star was known to the [[Hindu]]s as ''[[Angiras (sage)|Añgiras]]'', one of the [[Saptarishi|Seven Rishis]].<ref name=allen1899>{{cite book
 | last=Allen
 | first=R. H.
 | year=1963
 | author-link=Richard Hinckley Allen
 | title=Star Names: Their Lore and Meaning
 | url=https://archive.org/details/starnamestheirlo00alle/page/438
 | access-date=2012-09-04
 | edition=Reprint
 | publisher=Dover Publications Inc
 | location=New York
 | isbn=0-486-21079-0
 | page=[https://archive.org/details/starnamestheirlo00alle/page/438 438]
 | url-access=registration
 }}</ref>

In [[Chinese astronomy|Chinese]], {{lang|zh|北斗}} ({{lang|zh-Latn|Běi Dǒu}}), meaning ''[[Purple Forbidden enclosure|Northern Dipper]]'', refers to an [[Asterism (astronomy)|asterism]] equivalent to the Big Dipper. Consequently, the [[Chinese star names|Chinese name]] for Epsilon Ursae Majoris itself is {{lang|zh|北斗五}} ({{lang|zh-Latn|Běi Dǒu wu}}, {{langx|en|the Fifth Star of Northern Dipper}}) and {{lang|zh|玉衡}} ({{lang|zh-Latn|Yù Héng}}, {{langx|en|Star of Jade Sighting-Tube}}).<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0606/ap060615.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日] {{Webarchive|url=https://web.archive.org/web/20141102063635/http://aeea.nmns.edu.tw/2006/0606/ap060615.html |date=2014-11-02 }}</ref>

==Namesakes==
The [[United States Navy]]'s [[Crater class cargo ship]] {{USS|Allioth|AK-109}} was named after the star.

==See also==
* [[List of brightest stars]]
* [[List of nearest bright stars]]
* [[Lists of stars]]
* [[Historical brightest stars]]

==References==
{{reflist|refs=

<ref name=MAST>{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=8 December 2021}}</ref>

<ref name=morgan>{{cite journal|bibcode=1978MNRAS.183..701M|title=Observations of binary stars by speckle interferometry – I|journal=Monthly Notices of the Royal Astronomical Society|volume=183|issue=4|pages=701–710|last1=Morgan|first1=B. L.|last2=Beddoes|first2=D. R.|last3=Scaddan|first3=R. J.|last4=Dainty|first4=J. C.|year=1978|doi=10.1093/mnras/183.4.701|doi-access=free}}</ref>

<ref name=shulyak>{{cite journal|bibcode=2014MNRAS.443.1629S|title=Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities|journal=Monthly Notices of the Royal Astronomical Society|volume=443|issue=2|pages=1629|last1=Shulyak|first1=D.|last2=Paladini|first2=C.|last3=Causi|first3=G. Li|last4=Perraut|first4=K.|last5=Kochukhov|first5=O.|year=2014|arxiv=1406.6093|doi=10.1093/mnras/stu1259|doi-access=free |s2cid=96452769}}</ref>

<ref name=nakajima>{{cite journal|bibcode=2012AJ....143....2N|title=Potential Members of Stellar Kinematic Groups within 30 pc of the Sun|journal=The Astronomical Journal|volume=143|issue=1|pages=2|last1=Nakajima|first1=Tadashi|last2=Morino|first2=Jun-Ichi|year=2012|doi=10.1088/0004-6256/143/1/2|doi-access=free}}</ref>

<<!--<ref name=gray>{{cite journal|bibcode=2003AJ....126.2048G|title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I|journal=The Astronomical Journal|volume=126|issue=4|pages=2048|last1=Gray|first1=R. O.|last2=Corbally|first2=C. J.|last3=Garrison|first3=R. F.|last4=McFadden|first4=M. T.|last5=Robinson|first5=P. E.|year=2003|arxiv=astro-ph/0308182|doi=10.1086/378365|s2cid=119417105}}</ref>-->

<!--<ref name=vlbi>{{cite journal|bibcode=2016MNRAS.461..929K|title=Search for exoplanets and brown dwarfs with VLBI|journal=Monthly Notices of the Royal Astronomical Society|volume=461|issue=1|pages=929|last1=Katarzyński|first1=K.|last2=Gawroński|first2=M.|last3=Goździewski|first3=K.|year=2016|arxiv=1608.06719|doi=10.1093/mnras/stw1354|s2cid=119298606}}</ref>-->

<ref name=weakfield>{{cite journal|bibcode=2019A&A...621A..47K|title=Magnetic field topologies of the bright, weak-field Ap stars θ Aurigae and ∊ Ursae Majoris|journal=Astronomy and Astrophysics|volume=621|pages=A47|last1=Kochukhov|first1=O.|last2=Shultz|first2=M.|last3=Neiner|first3=C.|year=2019|arxiv=1811.04928|doi=10.1051/0004-6361/201834279|s2cid=119070948}}</ref>

<ref name=aaa474_2_653>{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>

<ref name=apjss192_1_2>{{citation | last1=Shaya | first1=Ed J. | last2=Olling | first2=Rob P. | title=Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue | journal=The Astrophysical Journal Supplement | volume=192 | issue=1 | page=2 |date=January 2011 | doi=10.1088/0067-0049/192/1/2 | bibcode=2011ApJS..192....2S |arxiv = 1007.0425 | s2cid=119226823 }}</ref>

<ref name=aass77_1_41>{{citation | last1=Tektunali | first1=H. G. | title=The spectrum of the CR star Epsilon Ursae Majoris | journal=Astrophysics and Space Science | volume=77 | issue=1 | pages=41–58 |date=June 1981 | doi=10.1007/BF00648756 | bibcode=1981Ap&SS..77...41T | s2cid=122817347 }}</ref>

<ref name=rgcrv>{{citation | last=Evans | first=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | title=The Revision of the General Catalogue of Radial Velocities | volume=30 | pages=57 | work=Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 | location=University of Toronto | publisher=[[International Astronomical Union]] | bibcode=1967IAUS...30...57E }}</ref>

<ref name=aaa393_897>{{citation | display-authors=1 | last1=Royer | first1=F. | last2=Grenier | first2=S. | last3=Baylac | first3=M.-O. | last4=Gómez | first4=A. E. | last5=Zorec | first5=J. | title=Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i | journal=Astronomy and Astrophysics | volume=393 | issue=3 | pages=897–911 |date=October 2002 | doi=10.1051/0004-6361:20020943 | bibcode=2002A&A...393..897R |arxiv = astro-ph/0205255 | s2cid=14070763 }}</ref>

<ref name="npoi">{{Cite journal |last1=Baines |first1=Ellyn K. |last2=Clark |first2=James H., III |last3=Schmitt |first3=Henrique R. |last4=Stone |first4=Jordan M. |last5=von Braun |first5=Kaspar |date=2023-12-01 |title=33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble |journal=The Astronomical Journal |volume=166 |issue=6 |pages=268 |doi=10.3847/1538-3881/ad08be |doi-access=free |bibcode=2023AJ....166..268B |issn=0004-6256}}</ref>

<ref name=clpl4_99>{{cite journal | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | year=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name="MNRASL385_1_L1">{{citation
 | last1     = Sokolov
 | first1    = N. A.
 | title     = Radial velocity study of the chemically peculiar star ɛ Ursae Majoris
 | journal   = [[Monthly Notices of the Royal Astronomical Society: Letters]]
 | volume    = 385
 | issue     = 1
 | pages     = L1–L4
 |date=March 2008
 | doi       = 10.1111/j.1745-3933.2008.00419.x
 | doi-access = free
 | bibcode   = 2008MNRAS.385L...1S
 | arxiv     = 0904.3562
 | s2cid = 17104356
 | postscript = .
}}</ref>
}}
#{{note label|1728|1|^}}{{1728|title=Allioth}}

{{Stars of Ursa Major}}
{{Portal bar|Astronomy|Stars|Outer space}}
<!-- Properties -->
[[Category:Alpha2 Canum Venaticorum variables]]
[[Category:Ap stars]]
[[Category:A-type giants]]
[[Category:Ursa Major moving group]]
<!-- Location/Catalogues -->
[[Category:Big Dipper]]
[[Category:Ursa Major]]
[[Category:Bayer objects|Ursae Majoris, Epsilon]]
[[Category:Bright Star Catalogue objects|4905]]
[[Category:Durchmusterung objects|BD+56 1627]]
[[Category:Flamsteed objects|Ursae Majoris, 77]]
[[Category:Henry Draper Catalogue objects|112185]]
[[Category:Hipparcos objects|062956]]
[[Category:Stars with proper names|Alioth]]