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  | gravity    = 3.59<ref name="npoi"/>
  | gravity    = 3.59<ref name="npoi"/>
  | metal_fe    = +0.00<ref name=aass77_1_41/>
  | metal_fe    = +0.00<ref name=aass77_1_41/>
| rotation    = {{val|5.088631|(18)}}<ref name=Shulyak2010/> days
  | rotational_velocity = 33<ref name=aaa393_897/>
  | rotational_velocity = 33<ref name=aaa393_897/>
  | age_myr    = 300<ref name=nakajima/>
  | age_myr    = 300<ref name=nakajima/>
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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.
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"/>
It has long been suspected that Epsilon Ursae Majoris is a [[spectroscopic binary]], possibly with more than one companion.<ref name=morgan/>  A 2008 study suggested Alioth'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,<ref name=Shulyak2010/> 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 detected 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/>
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/>
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* [[Lists of stars]]
* [[Lists of stars]]
* [[Historical brightest stars]]
* [[Historical brightest stars]]
* [[List of nearest giant stars]]


==References==
==References==
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<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=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=aaa474_2_653>{{cite journal | 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=apjss192_1_2>{{cite journal | 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=aass77_1_41>{{cite journal | 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=Shulyak2010>{{Cite journal |last=Shulyak |first=D. |last2=Krtička |first2=J. |last3=Mikulášek |first3=Z. |last4=Kochukhov |first4=O. |last5=Lüftinger |first5=T. |date=2010-12-01 |title=Modelling the light variability of the Ap star ε Ursae Majoris |journal=Astronomy & Astrophysics |language=en |volume=524 |pages=A66 |doi=10.1051/0004-6361/201015094 |issn=0004-6361|arxiv=1009.1297 }}</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=rgcrv>{{cite journal | 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="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=aaa393_897>{{cite journal | 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|arxiv=2505.23514 }}</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=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
<ref name="MNRASL385_1_L1">{{cite journal
  | last1    = Sokolov
  | last1    = Sokolov
  | first1    = N. A.
  | first1    = N. A.
Line 154: Line 158:
  | arxiv    = 0904.3562
  | arxiv    = 0904.3562
  | s2cid = 17104356
  | s2cid = 17104356
| postscript = .
}}</ref>
}}</ref>
}}
}}
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[[Category:Hipparcos objects|062956]]
[[Category:Hipparcos objects|062956]]
[[Category:Stars with proper names|Alioth]]
[[Category:Stars with proper names|Alioth]]
[[Category:Population I stars]]
[[Category:Lucidae]]

Latest revision as of 09:18, 3 September 2025

Template:Short description Script error: No such module "other uses".

Alioth
Template:Location mark
Location of Alioth (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 1.77[2]
Characteristics
Spectral type A1III-IVp kB9
U−B Template:Engvar +0.02[2]
B−V Template:Engvar −0.02[2]
Variable type α2 CVn
Astrometry
Radial velocity (Rv)−9.3[3] km/s
Proper motion (μ) RA: +111.91 mas/yr[1]
Dec.: −8.24 mas/yr[1]
Parallax (π)39.51±0.20 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−0.2[4]
Details
Mass2.91[5] Template:Solar mass
RadiusTemplate:Val[6] Template:Solar radius
LuminosityTemplate:Val[6] Template:Solar luminosity
Surface gravity (log g)3.59[6] cgs
TemperatureTemplate:Val[6] K
Metallicity [Fe/H]+0.00[4] dex
RotationTemplate:Val[7] days
Rotational velocity (v sin i)33[8] km/s
Age300[9] Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist
Database references
SIMBADdata

Script error: No such module "Check for unknown parameters".

Alioth Template:IPAc-en, also called Epsilon Ursae Majoris, is a star in the northern constellation of Ursa Major. The designation is Latinised from ε Ursae Majoris and abbreviated Epsilon UMa or ε UMa.[10][11] Despite being designated "ε" (epsilon), it is the brightest star in the constellation and at magnitude 1.77 is the 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.<templatestyles src="Citation/styles.css"/>[1]

Physical characteristics

File:Sidney Hall - Urania's Mirror - Ursa Major.jpg
Book plate by Sidney Hall depicting Ursa Major's stars
File:EpsUMaLightCurve.png
A light curve for Epsilon Ursae Majoris, plotted from TESS data[12]

According to Hipparcos, Epsilon Ursae Majoris is Template:Convert from the Sun. Its spectral type is A1p; the "p" stands for peculiar, as its spectrum is characteristic of an α2 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 lines 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.[13] A 2008 study suggested Alioth'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 units.[14] It is now thought that the 5.1-day period is the rotation period of the star,[7] and no companions have been detected using the most modern equipment.[15] Observations of Alioth with the Navy Precision Optical Interferometer also did not detected a companion.[6]

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 that of the Earth.[16]

Name and etymology

ε Ursae Majoris (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)[17] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[18] 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 Hindus as Añgiras, one of the Seven Rishis.[19]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Northern Dipper, refers to an asterism equivalent to the Big Dipper. Consequently, the Chinese name for Epsilon Ursae Majoris itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx) and Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[20]

Namesakes

The United States Navy's Crater class cargo ship Template:USS was named after the star.

See also

References

Template:Reflist

  1. <templatestyles src="Citation/styles.css"/>^ Template:1728

Template:Stars of Ursa Major Template:Portal bar

  1. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named aaa474_2_653
  2. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named clpl4_99
  3. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named rgcrv
  4. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named aass77_1_41
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named apjss192_1_2
  6. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named npoi
  7. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Shulyak2010
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa393_897
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named nakajima
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named MAST
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named morgan
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named MNRASL385_1_L1
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named shulyak
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named weakfield
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日 Template:Webarchive
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