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{{Starbox begin
{{Starbox begin
| name=Alpha Ursae Majoris A/B
| name=Alpha Ursae Majoris
}}
⚫
{{Starbox image
| image=
{{Location mark
⚫
|image=Ursa Major constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=12|mark_link=Alpha Ursae majoris|x=555|y=343
}}
|caption=Location of α Ursae majoris (circled)
}}
}}
⚫
{{Starbox image
| image = {{Location map|100x100
⚫
|AlternativeMap=Ursa Major constellation map.svg
|caption=
|width=250
|lat=63.5 |long=55.5
|mark=Cercle rouge 100%.svg | marksize=12
|float=center
}}| caption = Stars of Ursa Major, including Dubhe
}}
}}
{{Starbox observe
{{Starbox observe
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}}
}}
{{Starbox character
{{Starbox character
| class = K0III<ref name=guenther>{{cite journal|bibcode=2000ApJ...530L..45G|title=Evolutionary Model and Oscillation Frequencies for α Ursae Majoris: A Comparison with Observations|journal=The Astrophysical Journal|volume=530|issue=1|pages=L45–L48|author1=Guenther|first1=D. B.|last2=Demarque|first2=P.|last3=Buzasi|first3=D.|last4=Catanzarite|first4=J.|last5=Laher|first5=R.|last6=Conrow|first6=T.|last7=Kreidl|first7=T.|year=2000|doi=10.1086/312473|pmid=10642202}}</ref> + F0V<ref name=msc/>
| class = G9III<ref name="KeenanMcNeil1989">{{cite journal|last1=Keenan|first1=Philip C.|last2=McNeil|first2=Raymond C.|title=The Perkins catalog of revised MK types for the cooler stars|journal=The Astrophysical Journal Supplement Series|volume=71|year=1989|pages=245|issn=0067-0049|doi=10.1086/191373|bibcode = 1989ApJS...71..245K }}</ref> + A7.5<ref name="ParsonsAke1998">{{cite journal|last1=Parsons|first1=Sidney B.|last2=Ake|first2=Thomas B.|title=Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. V. The EntireIUESample|journal=The Astrophysical Journal Supplement Series|volume=119|issue=1|year=1998|pages=83–104|issn=0067-0049|doi=10.1086/313152|bibcode = 1998ApJS..119...83P }}</ref>
| b-v = +1.07<ref name=clpl4_99/>
| b-v = +1.07<ref name=clpl4_99/>
| u-b = +0.93<ref name=clpl4_99/>
| u-b = +0.93<ref name=clpl4_99/>
| variable = Pulsating<ref name=buzasi>{{cite journal|bibcode=2000ApJ...532L.133B|title=The Detection of Multimodal Oscillations on α Ursae Majoris|journal=The Astrophysical Journal|volume=532|issue=2|pages=L133|author1=Buzasi|first1=D.|last2=Catanzarite|first2=J.|last3=Laher|first3=R.|last4=Conrow|first4=T.|last5=Shupe|first5=D.|last6=Gautier|first6=T. N.|last7=Kreidl|first7=T.|last8=Everett|first8=D.|year=2000|doi=10.1086/312573|pmid=10715242}}</ref>
| variable = Pulsating{{citation needed|date=August 2015}}
}}
}}
{{Starbox astrometry
{{Starbox astrometry
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{{Starbox visbin
{{Starbox visbin
| name = α UMa B
| name = α UMa B
| reference = {{citation needed|date=December 2011}}
| reference = <ref name=msc/>
| period = 44.4
| period = 44.4
| axis = 0.603
| axis = 0.603
| eccentricity = 0.4
| eccentricity = 0.4
| inclination = 152
| inclination = 180
| node = 2000
| node = 2000
| periastron = 1956.8
| periastron = 1958.000
}}<!--
}}
-->{{Starbox detail
{{Starbox detail
| component1 = α UMa A
| component1 = α UMa A
| mass =
| mass = 4.25<ref name=guenther/>
| radius =
| radius =
| luminosity =
| luminosity = 316<ref name=guenther/>
| temperature = 4,660<ref name=ajss74_1075/>
| temperature = 4,660<ref name=ajss74_1075/>
| gravity = 2.46<ref name=ajss74_1075/>
| gravity = 2.46<ref name=ajss74_1075/>
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| rotational_velocity = {{nowrap|2.6 ± 1.0}}<ref name=aj135_3_892/>
| rotational_velocity = {{nowrap|2.6 ± 1.0}}<ref name=aj135_3_892/>
| age_myr =
| age_myr =
| component2 = α UMa B
| mass2 = ~1.6<ref name=guenther/>
}}
}}
{{Starbox catalog
{{Starbox catalog
| names=Dubhe, Dubb, Ak, α&nbsp;Ursae Majoris, α&nbsp;UMa, Alpha&nbsp;UMa, 50&nbsp;UMa, [[Star catalogue#BD/CD/CPD|BD]]+62&nbsp;1161, [[Catalog of Components of Double and Multiple Stars|CCDM]]&nbsp;J11037+6145AB, [[Fifth Fundamental Catalogue|FK5]]&nbsp;417, [[Boss General Catalogue|GC]]&nbsp;15185, [[Henry Draper catalogue|HD]]&nbsp;95689, [[Hipparcos catalogue|HIP]]&nbsp;54061, [[Bright Star Catalogue|HR]]&nbsp;4301, [[PPM Star Catalogue|PPM]]&nbsp;17705, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;15384, [[Washington Double Star Catalog|WDS]]&nbsp;J11037+6145AB.<ref name=SIMBAD/>
| names=Dubhe, Ak, [[Nayer designation|α]]&nbsp;Ursae Majoris, α&nbsp;UMa, Alpha&nbsp;UMa, [[Flamsteed designation|50]]&nbsp;UMa, [[Bonner Durchmusterung|BD]]+62°1161, [[Catalog of Components of Double and Multiple Stars|CCDM]]&nbsp;J11037+6145AB, [[Fifth Fundamental Catalogue|FK5]]&nbsp;417, [[Boss General Catalogue|GC]]&nbsp;15185, [[Henry Draper catalogue|HD]]&nbsp;95689, [[Hipparcos catalogue|HIP]]&nbsp;54061, [[Bright Star Catalogue|HR]]&nbsp;4301, [[PPM Star Catalogue|PPM]]&nbsp;17705, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;15384, [[Washington Double Star Catalog|WDS]]&nbsp;J11037+6145AB<ref name=SIMBAD/>
}}
}}
{{Starbox reference
{{Starbox reference
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'''Alpha Ursae Majoris''' ('''Alpha&nbsp;UMa''', '''α&nbsp;Ursae Majoris''', '''α&nbsp;UMa''') is the second-brightest [[star]] in the [[constellation]] of [[Ursa Major]] (despite its [[Bayer designation]] of "alpha"). It has the traditional name '''Dubhe''', and a rarer name ''Ak.''
'''Alpha Ursae Majoris''' ('''Alpha&nbsp;UMa''', '''α&nbsp;Ursae Majoris''', '''α&nbsp;UMa''') is the second-brightest [[star]] in the [[constellation]] of [[Ursa Major]] (despite its [[Bayer designation]] of "alpha"). It has the traditional name '''Dubhe''', and a rarer name ''Ak.''


==Description==
This star forms part of the [[Big Dipper]] (also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards [[Polaris]], the North Star. Dubhe is about 123&nbsp;[[light year]]s away and is a [[giant star]] that has evolved away from the [[main sequence]] after consuming the hydrogen at its core. It is a [[spectroscopic binary]] with a [[main sequence]] companion ''α UMa B'' that has a [[stellar classification]] of K0V.<ref name=SimbadB/> The companion star orbits at a mean separation of about 23 [[astronomical unit]]s (AU) and completes an orbit every 44.4 years. More than 8,000&nbsp;AU distant from this pair is a second binary system that includes an F-type star, making this a four star system.<ref name=kaler/>
Alpha Ursae Majoris forms part of the [[Big Dipper]] (also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards [[Polaris]], the North Star. Dubhe is about 123&nbsp;[[light year]]s away and is a [[giant star]] that has evolved away from the [[main sequence]] after consuming the hydrogen at its core. It is a [[spectroscopic binary]] with a [[main sequence]] companion ''α UMa B'' that has a [[stellar classification]] of F0V. The companion star orbits at a mean separation of about 23 [[astronomical unit]]s (AU) and completes an orbit every 44.4 years.<ref name=msc>{{cite journal|bibcode=1997A&AS..124...75T|title=MSC - a catalogue of physical multiple stars|journal=A & A Supplement series|volume=124|pages=75|author1=Tokovinin|first1=A. A.|year=1997|doi=10.1051/aas:1997181}}</ref> The yellow giant primary star shows rapid tiny pulsations at many frequencies, its brightness changing by less than a hundredth of a magnitude.<ref name=buzasi/>

There is another spectroscopic binary 8 arc minutes distant, a 7th magnitude pair showing an F8 spectral type. It is sometimes referred to as Alpha Ursae majoris C, but is separately catalogued as HD 95638.<ref name=msc/>


Although it is part of the constellation of Ursa Major, it does not form part of the [[Ursa Major Moving Group]] of stars that have a common motion through space.<ref name=motz>{{cite book|page=39|title=The Constellations: An Enthusiast's Guide To The Night Sky|last=Motz|first=Lloyd|last2=Nathanson|first2=Carol|publisher=Doubleday|year=1988|isbn=978-0385176002|authorlink=Lloyd Motz}}</ref>
Although it is part of the constellation of Ursa Major, it does not form part of the [[Ursa Major Moving Group]] of stars that have a common motion through space.<ref name=motz>{{cite book|page=39|title=The Constellations: An Enthusiast's Guide To The Night Sky|last=Motz|first=Lloyd|last2=Nathanson|first2=Carol|publisher=Doubleday|year=1988|isbn=978-0385176002|authorlink=Lloyd Motz}}</ref>

Revision as of 19:36, 16 September 2015

}}


Alpha Ursae Majoris
Location of α Ursae majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 11h 03m 43.67152s[1]
Declination +61° 45′ 03.7249″[1]
Apparent magnitude (V) 1.79[2]
Characteristics
Spectral type K0III[3] + F0V[4]
U−B color index +0.93[2]
B−V color index +1.07[2]
Variable type Pulsating[5]
Astrometry
Radial velocity (Rv)–9[6] km/s
Proper motion (μ) RA: –134.11[1] mas/yr
Dec.: –34.70[1] mas/yr
Parallax (π)26.54±0.48 mas[1]
Distance123 ± 2 ly
(37.7 ± 0.7 pc)
Absolute magnitude (MV)–1.10 ± 0.04[7]
Orbit[4]
Companionα UMa B
Period (P)44.4 yr
Semi-major axis (a)0.603″
Eccentricity (e)0.4
Inclination (i)180°
Longitude of the node (Ω)2000°
Periastron epoch (T)1958.000
Details
α UMa A
Mass4.25[3] M☉
Luminosity316[3] L☉
Surface gravity (log g)2.46[8] cgs
Temperature4,660[8] K
Metallicity [Fe/H]–0.20 ± 0.07[8] dex
Rotational velocity (v sin i)2.6 ± 1.0[7] km/s
α UMa B
Mass~1.6[3] M☉
Other designations
Dubhe, Ak, α Ursae Majoris, α UMa, Alpha UMa, 50 UMa, BD+62°1161, CCDM J11037+6145AB, FK5 417, GC 15185, HD 95689, HIP 54061, HR 4301, PPM 17705, SAO 15384, WDS J11037+6145AB[9]
Database references
SIMBADdata

Alpha Ursae Majoris (Alpha UMa, α Ursae Majoris, α UMa) is the second-brightest star in the constellation of Ursa Major (despite its Bayer designation of "alpha"). It has the traditional name Dubhe, and a rarer name Ak.

Description

Alpha Ursae Majoris forms part of the Big Dipper (also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards Polaris, the North Star. Dubhe is about 123 light years away and is a giant star that has evolved away from the main sequence after consuming the hydrogen at its core. It is a spectroscopic binary with a main sequence companion α UMa B that has a stellar classification of F0V. The companion star orbits at a mean separation of about 23 astronomical units (AU) and completes an orbit every 44.4 years.[4] The yellow giant primary star shows rapid tiny pulsations at many frequencies, its brightness changing by less than a hundredth of a magnitude.[5]

There is another spectroscopic binary 8 arc minutes distant, a 7th magnitude pair showing an F8 spectral type. It is sometimes referred to as Alpha Ursae majoris C, but is separately catalogued as HD 95638.[4]

Although it is part of the constellation of Ursa Major, it does not form part of the Ursa Major Moving Group of stars that have a common motion through space.[10]

Name and etymology

In culture

Dubhe is the official star of the State of Utah. USS Dubhe (ID-2562) was a ship in the United States navy. The Danish National Home Guard Navy ship MHV 806 is named Dubhe.

Photos

Dubhe A & B
Dubhe "A" and faint companion binaries

References

  1. ^ a b c d e van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. ^ a b c Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J
  3. ^ a b c d Guenther, D. B.; Demarque, P.; Buzasi, D.; Catanzarite, J.; Laher, R.; Conrow, T.; Kreidl, T. (2000). "Evolutionary Model and Oscillation Frequencies for α Ursae Majoris: A Comparison with Observations". The Astrophysical Journal. 530 (1): L45 – L48. Bibcode:2000ApJ...530L..45G. doi:10.1086/312473. PMID 10642202.
  4. ^ a b c d Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". A & A Supplement series. 124: 75. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181.
  5. ^ a b Buzasi, D.; Catanzarite, J.; Laher, R.; Conrow, T.; Shupe, D.; Gautier, T. N.; Kreidl, T.; Everett, D. (2000). "The Detection of Multimodal Oscillations on α Ursae Majoris". The Astrophysical Journal. 532 (2): L133. Bibcode:2000ApJ...532L.133B. doi:10.1086/312573. PMID 10715242.
  6. ^ Wilson, Ralph Elmer (1953), General catalogue of stellar radial velocities, Carnegie Institution of Washington, Bibcode:1953QB901.W495.....
  7. ^ a b Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:0711.4984, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892
  8. ^ a b c McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527
  9. ^ "DUBHE -- Spectroscopic binary", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-23
  10. ^ Motz, Lloyd; Nathanson, Carol (1988). The Constellations: An Enthusiast's Guide To The Night Sky. Doubleday. p. 39. ISBN 978-0385176002.
  11. ^ a b 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)
  12. ^ Template:Zh icon AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日

Cite error: A list-defined reference named "kaler" is not used in the content (see the help page).

Cite error: A list-defined reference named "SimbadB" is not used in the content (see the help page).
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