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Coordinates: Sky map 11h 01m 50.5s, +56° 22′ 57″
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{{short description|Star in the constellation Ursa Major}}
{{Starbox begin
{{Starbox begin
| name = Beta Ursae Majoris
| name = Merak
}}
}}
{{Starbox image
{{Starbox image
| image={{Location map|100x100
| image=
{{Location mark
|AlternativeMap=Ursa Major IAU.svg
⚫
| image=Ursa Major constellation map.svg
|caption=
| float=center | width=250 | position=right
|width=320
| mark=Red circle.svg | mark_width=10 | mark_link=β UMa
|lat=63.57 |long=49.82
| x%=57.2 | y%=47.0
|mark=Cercle rouge 100%.svg | marksize=12
}}
|float=center
}}| caption=Merak in Ursa Major.
| caption=Location of Merak (circled)
}}
}}
{{Starbox observe
{{Starbox observe
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}}
}}
{{ Starbox character
{{ Starbox character
| class = A1IVps
| class = A1IVps<ref name=phillips/>
| variable = Suspected
| variable = Suspected
| b-v = -0.02<ref name=clpl4_99/>
| b-v = -0.02<ref name=clpl4_99/>
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| p_error = 0.16
| p_error = 0.16
| parallax_footnote = <ref name=aaa474_2_653/>
| parallax_footnote = <ref name=aaa474_2_653/>
| absmag_v =
| absmag_v = +0.61<ref name=Eggen1998/>
}}
}}
{{ Starbox detail
{{ Starbox detail
| mass = 2.7<ref name=apj663_1_365/>
| source = <ref name=Acharyya2024/>
| radius = {{nowrap|3.021 ± 0.038}}<ref name=apj746_1_101/>
| mass = {{val|2.56|0.05}}
| radius = {{val|2.81|0.24}}
| luminosity = {{nowrap|63.015 ± 1.307}}<ref name=apj746_1_101/>
| temperature = {{nowrap|9377 ± 75}}<ref name=apj746_1_101/>
| luminosity = {{nowrap|63.5|1.4}}
| temperature = {{val|9,700|400|fmt=commas}}
| age_myr = {{nowrap|500 ± 100}}<ref name=aaa442_2_563/>
| age_myr = {{val|390|61}}
| gravity = 3.83<ref name=aaa442_2_563/>
| gravity = {{val|3.93|0.08}}
| metal_fe =
| metal_fe =
| rotational_velocity = 46<ref name=aaa463_2_671/>
| rotational_velocity = {{val|47|3}}
}}
}}
{{ Starbox catalog
{{ Starbox catalog
| names=Merak, Mirak,<ref name=allen1899/> β&nbsp;Ursae Majoris, β&nbsp;UMa, Beta&nbsp;UMa, 48&nbsp;Ursae Majoris, [[Bonner Durchmusterung|BD]]+57°1302, [[Fifth Fundamental Catalogue|FK5]]&nbsp;416, [[Boss General Catalogue|GC]]&nbsp;15145, [[Henry Draper Catalogue|HD]]&nbsp;95418, [[Hipparcos catalogue|HIP]]&nbsp;53910, [[Bright Star Catalogue|HR]]&nbsp;4295, [[PPM Star Catalogue|PPM]]&nbsp;32912, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;27876.<ref name=SIMBAD/>
| names=Merak, Mirak,<ref name=allen1899/> β&nbsp;Ursae Majoris, β&nbsp;UMa, Beta&nbsp;UMa, 48&nbsp;Ursae Majoris, [[Bonner Durchmusterung|BD]]+57°1302, [[Fifth Fundamental Catalogue|FK5]]&nbsp;416, [[Boss General Catalogue|GC]]&nbsp;15145, [[Henry Draper Catalogue|HD]]&nbsp;95418, [[Hipparcos catalogue|HIP]]&nbsp;53910, [[Bright Star Catalogue|HR]]&nbsp;4295, [[PPM Star Catalogue|PPM]]&nbsp;32912, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;27876<ref name=SIMBAD/>
}}
}}
{{Starbox reference
{{Starbox reference
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}}
}}
{{ Starbox end }}
{{ Starbox end }}
[[File:Sun to Arcturus comparison.jpg|thumb|Size comparison between the [[Sun]], Beta Ursae Majoris, [[Pollux (star)|Pollux]], and [[Arcturus]].]]
⚫
'''Merak''' {{IPAc-en|'|m|ɪər|æ|k}}, also called '''Beta Ursae Majoris''' ('''β&nbsp;Ursae Majoris''', abbreviated '''Beta&nbsp;UMa''', '''β&nbsp;UMa'''),<ref name=Kunitzsch/><ref name="IAU-CSN"/> is a [[star]] in the northern [[constellation]] of [[Ursa Major]].


⚫
The [[apparent visual magnitude]] of this star is +2.37,<ref name=clpl4_99/> which means it is readily visible to the naked eye. It is more familiar to [[northern hemisphere]] observers as one of the "pointer stars" in the [[Big Dipper]], or the Plough (UK), which is a prominent [[Asterism (astronomy)|asterism]] of seven stars that forms part of the larger constellation. Extending an imaginary straight line from this star through the nearby [[Alpha Ursae Majoris]] (Dubhe) extends to [[Polaris]], the north star.
⚫
'''Beta Ursae Majoris''' ('''β&nbsp;Ursae Majoris''', abbreviated '''Beta&nbsp;UMa''', '''β&nbsp;UMa'''), also named '''Merak''' (meaning hope in [[Turkish language|Turkish]]),<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |accessdate=28 July 2016}}</ref> is a [[star]] in the northern [[circumpolar constellation]] of [[Ursa Major]].


==Spectral classification==
⚫
The [[apparent visual magnitude]] of this star is +2.37,<ref name=clpl4_99/> which means it is readily visible to the naked eye. It is more familiar to [[northern hemisphere]] observers as one of the "pointer stars" in [[Big Dipper| the Big Dipper or the Plough (UK)]], which is a prominent [[Asterism (astronomy)|asterism]] of seven stars that forms part of the larger constellation. Extending an imaginary straight line from this star through the nearby [[Alpha Ursae Majoris]] (Dubhe) extends to [[Polaris]], the north star.
In 1943, β Ursae Majoris was listed as a spectral standard for the class of A1&nbsp;V.<ref name=mk/> When improved instruments made it possible to identify subgiant [[luminosity class]]es for early A-class stars, β Ursae Majoris was assigned that class A0&nbsp;IV.<ref name=barry/> This was later revised to A1&nbsp;IV.<ref name=phillips/> It is considered to be a mild [[Am star]], a type of [[chemically peculiar star]] with unusually strong lines of certain metallic elements.<ref name=renson/>


==Properties==
==Properties==
Based upon [[parallax]] measurements of this star, it is located at a distance of {{Convert|79.7|ly|pc|abbr=off|lk=on}} from the [[Sun]]. The [[spectrum]] shows this to have a [[stellar classification]] of A1&nbsp;V,<ref name=apj663_1_365/> making it a fairly typical [[main sequence]] star that is generating energy through the [[thermonuclear fusion]] of hydrogen at its core. The [[effective temperature]] of the outer envelope is about 9,225&nbsp;K,<ref name=apj663_1_365/> giving it a white-hued glow that is typical for [[A-type star]]s.<ref name=csiro/> It is larger than the Sun, with about 2.7 times the [[Solar mass|mass]] and 2.84 times the [[Solar radius]]. If they were viewed from the same distance, Beta Ursae Majoris would appear much brighter than the Sun, as it is radiating 68 times the [[solar luminosity|Sun's luminosity]].<ref name=apj663_1_365/><ref name=apj660_2_1556/>
Based upon [[parallax]] measurements, β Ursae Majoris is located at a distance of {{Convert|79.7|ly|pc|abbr=off|lk=on}} from the [[Sun]]. It is a [[subgiant]], a star that has exhausted the hydrogen in its core and is now cooling as it generates energy through the [[thermonuclear fusion]] of hydrogen in a shell outside the core. The [[effective temperature]] of the outer envelope is about 9,225&nbsp;K,<ref name=apj663_1_365/> giving it a white-hued glow that is typical for [[A-type star]]s.<ref name=csiro/> It is larger than the Sun, with about 2.7 times the [[Solar mass|mass]] and 2.84 times the [[solar radius]]. If they were viewed from the same distance, Beta Ursae Majoris would appear much brighter than the Sun, as it is radiating 68 times the [[solar luminosity|Sun's luminosity]].<ref name=apj663_1_365/><ref name=apj660_2_1556/>


Observation of the star in the [[infrared]] reveal an [[infrared excess|excess emission]] that suggests the presence of a circumstellar [[debris disk]] of orbiting dust,<ref name=apj663_1_365/> much like those discovered around [[Fomalhaut]] and [[Vega]] The mean temperature of this disk is 120&nbsp;K,<ref name=apj660_2_1556/> indicating that it is centered at a radius of 47&nbsp;[[Astronomical unit|AU]] from the host star.<ref name=apj663_1_365/> The dust has an estimated mass of about 0.27% the mass of the Earth.<ref name=apj660_2_1556/>
Observation of the star in the [[infrared]] reveal an [[infrared excess|excess emission]] that suggests the presence of a circumstellar [[debris disk]] of orbiting dust,<ref name=apj663_1_365/> much like those discovered around [[Fomalhaut]] and [[Vega]]. The mean temperature of this disk is 120&nbsp;K,<ref name=apj660_2_1556/> indicating that it is centered at a radius of 47&nbsp;[[Astronomical unit|AU]] from the host star.<ref name=apj663_1_365/> The dust has an estimated mass of about 0.27% the mass of the Earth.<ref name=apj660_2_1556/>


Beta Ursae Majoris is one of five stars in the Big Dipper that form a part of a loose [[open cluster]] called the [[Ursa Major moving group]], sharing the same region of space and not just the same patch of sky from Earth's perspective. This group has an estimated age of about (500 ± 100) million years. As the members of this group share a common origin and motion through space, this yields an estimate for the age of Beta Ursae Majoris.<ref name=aaa442_2_563/> Two stars are known to be located in relatively close proximity: 37 Ursae Majoris at {{Convert|5.2|ly|pc}} and [[Gamma Ursae Majoris]] at {{Convert|11.0|ly|pc}}; much closer to each other than these stars are to the Earth.<ref name=apjss192_1_2/>
Beta Ursae Majoris is one of five stars in the Big Dipper that form a part of a loose [[open cluster]] called the [[Ursa Major moving group]], sharing the same region of space and not just the same patch of sky from Earth's perspective. This group has an estimated age of about 500 (± 100) million years. As the members of this group share a common origin and motion through space, this yields an estimate for the age of Beta Ursae Majoris.<ref name=aaa442_2_563/> Two stars are known to be located in relatively close proximity: 37 Ursae Majoris at {{Convert|5.2|ly|pc}} and [[Gamma Ursae Majoris]] at {{Convert|11|ly|pc}}; much closer to each other than these stars are to the Earth.<ref name=apjss192_1_2/>


==Nomenclature==
==Nomenclature==
''β&nbsp;Ursae Majoris'' ([[Latinisation of names|Latinised]] to ''Beta Ursae Majoris'') is the star's [[Bayer designation]].
''β&nbsp;Ursae Majoris'' ([[Latinisation of names|Latinised]] to ''Beta Ursae Majoris'') is the star's [[Bayer designation]].


It bore the traditional name ''Merak'' derived from the [[Arabic]] المراق ''al-maraqq'' 'the loins' (of the bear).<ref name=allen1899/> In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|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)|accessdate=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 | title=Bulletin of the IAU Working Group on Star Names, No. 1 |accessdate=28 July 2016}}</ref> included a table of the first two batches of names approved by the WGSN; which included ''Merak'' for this star.
It bore the traditional name ''Merak'' derived from the [[Arabic]] المراق ''al-marāqq'' 'the loins' (of the bear).<ref name=allen1899/> In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Merak'' for this star.<ref name="WGSN1"/>


The [[Hindu]]s called the star ''[[Pulaha]]'', one of the [[Saptarishi|Seven Rishis]].<ref name=allen1899/>
The [[Hindus]] called the star ''[[Pulaha]]'', one of the [[Saptarishi|Seven Rishis]].<ref name=allen1899/>


In [[Chinese language|Chinese]], {{lang|zh|北斗}} ({{lang|zh-Latn|Běi Dǒu}}), meaning ''[[Purple Forbidden enclosure|Northern Dipper]]'', refers to an asterism consisting of Beta Ursae Majoris, [[Alpha Ursae Majoris]], [[Gamma Ursae Majoris]], [[Delta Ursae Majoris]], [[Epsilon Ursae Majoris]], [[Zeta Ursae Majoris]] and [[Eta Ursae Majoris]]. Consequently, Beta Ursae Majoris itself is known as {{lang|zh|北斗二}} ({{lang|zh-Latn|Běi Dǒu èr}}, {{lang-en|the Second Star of Northern Dipper}}) and {{lang|zh|天璇}} ({{lang|zh-Latn|Tiān Xuán}}, {{lang-en|Star of Celestial Rotating Jade}}).<ref>{{zh icon}} [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]</ref>
In [[Chinese astronomy|Chinese]], {{lang|zh|[[wikt:北斗|北斗]]}} ({{lang|zh-Latn|Běi Dǒu}}), meaning ''[[Purple Forbidden enclosure|Northern Dipper]]'', refers to an asterism equivalent to the Big Dipper. Consequently, the [[Chinese star names|Chinese name]] for Beta Ursae Majoris itself is {{lang|zh|[[wikt:北斗二|北斗二]]}} ({{lang|zh-Latn|Běi Dǒu èr}}, {{langx|en|the Second Star of Northern Dipper}}) and {{lang|zh|[[wikt:天璇|天璇]]}} ({{lang|zh-Latn|Tiān Xuán}}, {{langx|en|Star of Celestial Rotating Jade}}).<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>


==In culture==
==In culture==
[[USS Merak (1918)]] and [[USS Merak (AF-21)]], both of [[United States]] navy ship.
[[USS Merak|USS ''Merak'' (1918)]] and [[USS Merak (AF-21)|USS ''Merak'' (AF-21)]] are both [[United States]] navy ships.


==See also==
In the original ''[[Star Trek]]'' series episode [[The Cloud Minders]], the planet "Merak II" is said to be suffering from a botanical plague that can only be treated by the use of the mineral zenite.
* [[Lists of stars]]

* [[List of brightest stars]]
The video game ''[[Devil Survivor 2]]'' features Merak, alongside the other stars of the Big Digger, as the Septentrione, strange beings that appear in Japan on each day of the game. Merak features on the 2nd day in Osaka, Japan.
* [[List of nearest bright stars]]

* [[Historical brightest stars]]
In the anime ''[[Saint Seiya]]'', also known as ''Knights of the Zodiac'', the ''[[List of Saint Seiya anime-only characters#Odin's God Warriors|God Warriors]]'' are the main antagonists during the Asgard arc, each star of the [[Big Dipper]] serves as a guardian for each ''God Warrior''. Hagen is the name of the ''God Warrior'' representing the star Beta Merak.


==References==
==References==
{{reflist|30em|refs=
{{reflist|30em|refs=


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<ref name=Acharyya2024>{{Cite journal |last1=Acharyya |first1=A. |last2=Aufdenberg |first2=J. P. |last3=Bangale |first3=P. |last4=Bartkoske |first4=J. T. |last5=Batista |first5=P. |last6=Benbow |first6=W. |last7=Chromey |first7=A. J. |last8=Davis |first8=J. D. |last9=Feng |first9=Q. |last10=Foote |first10=G. M. |last11=Furniss |first11=A. |last12=Hanlon |first12=W. |last13=Hinrichs |first13=C. E. |last14=Holder |first14=J. |last15=Jin |first15=W. |date=2024-04-26 |title=An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory |journal=The Astrophysical Journal |volume=966 |issue=1 |pages=28 |doi=10.3847/1538-4357/ad2b68 |doi-access=free |arxiv=2401.01853 |bibcode=2024ApJ...966...28A |issn=0004-637X}}</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 }}</ref>


<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>
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<ref name=rgcrv>{{cite conference | last1=Evans | first1=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | contribution=The Revision of the General Catalogue of Radial Velocities | title=Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 | journal=Determination of Radial Velocities and their Applications | volume=30 | pages=57 | location=University of Toronto | publisher=International Astronomical Union | bibcode=1967IAUS...30...57E }}</ref>


<ref name=aaa463_2_671>{{citation | last1=Royer | first1=F. | last2=Zorec | first2=J. | last3=Gómez | first3=A. E. | title=Rotational velocities of A-type stars. III. Velocity distributions | journal=Astronomy and Astrophysics | volume=463 | issue= 2 | pages=671–682 |date=February 2007 | doi=10.1051/0004-6361:20065224 | bibcode=2007A&A...463..671R |arxiv = astro-ph/0610785 }}</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=Eggen1998>{{citation
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⚫
<ref name=rgcrv>{{cite conference | last1=Evans | first1=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | contribution=The Revision of the General Catalogue of Radial Velocities | title=Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 | journal=Determination of Radial Velocities and Their Applications | volume=30 | pages=57 | location=University of Toronto | publisher=[[International Astronomical Union]] | bibcode=1967IAUS...30...57E }}</ref>


<ref name=clpl4_99>{{citation | last1=Johnson | display-authors=1 | 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 | date=1966 | bibcode=1966CoLPL...4...99J }}</ref>
<ref name=clpl4_99>{{citation | last1=Johnson | display-authors=1 | 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 | date=1966 | bibcode=1966CoLPL...4...99J }}</ref>


<ref name=apj663_1_365>{{citation | display-authors=1 | last1=Wyatt | first1=M. C. | last2=Smith | first2=R. | last3=Su | first3=K. Y. L. | last4=Rieke | first4=G. H. | last5=Greaves | first5=J. S. | last6=Beichman | first6=C. A. | last7=Bryden | first7=G. | title=Steady State Evolution of Debris Disks around A Stars | journal=The Astrophysical Journal | volume=663 | issue=1 | pages=365–382 |date=July 2007 | doi=10.1086/518404 | bibcode=2007ApJ...663..365W |arxiv = astro-ph/0703608 }}</ref>
<ref name=apj663_1_365>{{citation | display-authors=1 | last1=Wyatt | first1=M. C. | last2=Smith | first2=R. | last3=Su | first3=K. Y. L. | last4=Rieke | first4=G. H. | last5=Greaves | first5=J. S. | last6=Beichman | first6=C. A. | last7=Bryden | first7=G. | title=Steady State Evolution of Debris Disks around A Stars | journal=The Astrophysical Journal | volume=663 | issue=1 | pages=365–382 |date=July 2007 | doi=10.1086/518404 | bibcode=2007ApJ...663..365W |arxiv = astro-ph/0703608 | s2cid=18883195 }}</ref>


<ref name=apj660_2_1556>{{citation | display-authors=1 | last1=Rhee | first1=Joseph H. | last2=Song | first2=Inseok | last3=Zuckerman | first3=B. | last4=McElwain | first4=Michael | title=Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs | journal=The Astrophysical Journal | volume=660 | issue=2 | pages=1556–1571 |date=May 2007 | doi=10.1086/509912 | bibcode=2007ApJ...660.1556R |arxiv = astro-ph/0609555 }}</ref>
<ref name=apj660_2_1556>{{citation | display-authors=1 | last1=Rhee | first1=Joseph H. | last2=Song | first2=Inseok | last3=Zuckerman | first3=B. | last4=McElwain | first4=Michael | title=Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs | journal=The Astrophysical Journal | volume=660 | issue=2 | pages=1556–1571 |date=May 2007 | doi=10.1086/509912 | bibcode=2007ApJ...660.1556R |arxiv = astro-ph/0609555 | s2cid=11879505 }}</ref>


<ref name=aaa442_2_563>{{citation | last1=Monier | first1=R. | title=Abundances of a sample of A and F-type dwarf members of the Ursa Major Group | journal=Astronomy and Astrophysics | volume=442 | issue=2 | pages=563–566 |date=November 2005 | doi=10.1051/0004-6361:20053222 | bibcode=2005A&A...442..563M }}</ref>
<ref name=aaa442_2_563>{{citation | last1=Monier | first1=R. | title=Abundances of a sample of A and F-type dwarf members of the Ursa Major Group | journal=Astronomy and Astrophysics | volume=442 | issue=2 | pages=563–566 |date=November 2005 | doi=10.1051/0004-6361:20053222 | bibcode=2005A&A...442..563M | doi-access=free }}</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 }}</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=SIMBAD>{{citation | title=MERAK -- Variable Star | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=beta+ursae+majoris | accessdate=2012-01-01 }}</ref>
<ref name=SIMBAD>{{citation | title=MERAK -- Variable Star | work=SIMBAD | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=beta+ursae+majoris | access-date=2012-01-01 }}</ref>


<ref name=allen1899>{{citation | first1=Richard Hinckley | last1=Allen | title=Star-names and their meanings | journal=New York | publisher=G. E. Stechert | date=1899 | page=438 | url=https://books.google.com/books?id=5xQuAAAAIAAJ&pg=PA438 | bibcode=1899sntm.book.....A }}</ref>
<ref name=allen1899>{{citation | first1=Richard Hinckley | last1=Allen | title=Star-names and their meanings | journal=New York | publisher=G. E. Stechert | date=1899 | page=438 | url=https://books.google.com/books?id=5xQuAAAAIAAJ&pg=PA438 | bibcode=1899sntm.book.....A }}</ref>


<ref name=csiro>{{citation|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |deadurl=yes |archiveurl=http://www.webcitation.org/6630AbtJZ?url=http%3A%2F%2Foutreach.atnf.csiro.au%2Feducation%2Fsenior%2Fastrophysics%2Fphotometry_colour.html |archivedate=2012-03-10 |df= }}</ref>
<ref name=csiro>{{citation |title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=[[Commonwealth Scientific and Industrial Research Organisation]] |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=2012-03-18 }}</ref>


<ref name=phillips>{{cite journal|bibcode=2010MNRAS.403.1089P|title=Target selection for the SUNS and DEBRIS surveys for debris discs in the solar neighbourhood|journal=Monthly Notices of the Royal Astronomical Society|volume=403|issue=3|pages=1089|last1=Phillips|first1=N. M.|last2=Greaves|first2=J. S.|last3=Dent|first3=W. R. F.|last4=Matthews|first4=B. C.|last5=Holland|first5=W. S.|last6=Wyatt|first6=M. C.|last7=Sibthorpe|first7=B.|year=2010|arxiv=0911.3426|doi=10.1111/j.1365-2966.2009.15641.x|doi-access=free |s2cid=119262858}}</ref>
⚫
<ref name=apj746_1_101>{{citation | display-authors=1 | last1=Boyajian | first1=Tabetha S. | last2=McAlister | first2=Harold A. | last3=van Belle | first3=Gerard | last4=Gies | first4=Douglas R. | last5=ten Brummelaar | first5=Theo A. | last6=von Braun | first6=Kaspar | last7=Farrington | first7=Chris | last8=Goldfinger | first8=P. J. | last9=O'Brien | first9=David | last10=Parks | first10=J. Robert | last11=Richardson | first11=Noel D. | last12=Ridgway | first12=Stephen | last13=Schaefer | first13=Gail | last14=Sturmann | first14=Laszlo | last15=Sturmann | first15=Judit | last16=Touhami | first16=Yamina | last17=Turner | first17=Nils H. | last18=White | first18=Russel | title=Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars | journal=The Astrophysical Journal | volume=746 | issue=1 | page=101 |date=February 2012 | doi=10.1088/0004-637X/746/1/101 | bibcode=2012ApJ...746..101B |arxiv = 1112.3316 }}. See Table 10.</ref>

<ref name=mk>{{cite journal|bibcode=1943assw.book.....M|title=An atlas of stellar spectra, with an outline of spectral classification|journal=Chicago|last1=Morgan|first1=William Wilson|last2=Keenan|first2=Philip Childs|last3=Kellman|first3=Edith|year=1943}}</ref>

<ref name=barry>{{cite journal|bibcode=1970ApJS...19..281B|title=Spectral Classification of a and F Stars|journal=The Astrophysical Journal Supplement Series|volume=19|pages=281|last1=Barry|first1=Don C.|year=1970|doi=10.1086/190209}}</ref>

<ref name=renson>{{cite journal|bibcode=2009A&A...498..961R|title=Catalogue of Ap, HGMN and Am stars|journal=Astronomy and Astrophysics|volume=498|issue=3|pages=961|last1=Renson|first1=P.|last2=Manfroid|first2=J.|year=2009|doi=10.1051/0004-6361/200810788|url=https://zenodo.org/record/890529|doi-access=free}}</ref>

<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=https://www.iau.org/public/themes/naming_stars/ | title=IAU Catalog of Star Names |access-date=28 Apr 2019}}</ref>

<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref>


}}
}}


{{Stars of Ursa Major}}
{{Stars of Ursa Major}}
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}
{{Sky|11|01|50.5|+|56|22|57|1000000000}}
{{Sky|11|01|50.5|+|56|22|57|1000000000}}


<!-- Properties -->
⚫
[[Category:A-type subgiants]]
[[Category:Suspected variables]]
⚫
[[Category:Ursa Major moving group]]
<!-- Identifiers -->
[[Category:Stars with proper names|Merak]]
[[Category:Bayer objects|Ursae Majoris, Beta]]
[[Category:Bayer objects|Ursae Majoris, Beta]]
[[Category:Ursa Major]]
[[Category:Big Dipper]]
[[Category:Big Dipper]]
[[Category:Henry Draper Catalogue objects|095418]]
[[Category:Durchmusterung objects|BD+57 1302]]
⚫
[[Category:Ursa Major (constellation)]]
⚫
[[Category:Stars with proper names]]
⚫
[[Category:A-type subgiants]]
[[Category:Flamsteed objects|Ursae Majoris, 48]]
[[Category:Flamsteed objects|Ursae Majoris, 48]]
[[Category:HR objects|4295]]
[[Category:Henry Draper Catalogue objects|095418]]
[[Category:Hipparcos objects|053910]]
[[Category:Hipparcos objects|053910]]
[[Category:Durchmusterung objects|BD+57 1302]]
[[Category:Bright Star Catalogue objects|4295]]
[[Category:Suspected variables]]
[[Category:Am stars]]

Latest revision as of 13:56, 6 January 2025

Merak
Location of Merak (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 11h 01m 50.47654s[1]
Declination +56° 22′ 56.7339″[1]
Apparent magnitude (V) +2.37[2]
Characteristics
Spectral type A1IVps[3]
U−B color index +0.00[2]
B−V color index -0.02[2]
Variable type Suspected
Astrometry
Radial velocity (Rv)-12.0[4] km/s
Proper motion (μ) RA: +81.43[1] mas/yr
Dec.: +33.49[1] mas/yr
Parallax (π)40.90 ± 0.16 mas[1]
Distance79.7 ± 0.3 ly
(24.45 ± 0.10 pc)
Absolute magnitude (MV)+0.61[5]
Details[6]
Mass2.56±0.05 M☉
Radius2.81±0.24 R☉
Luminosity63.5 L☉
Surface gravity (log g)3.93±0.08 cgs
Temperature9,700±400 K
Rotational velocity (v sin i)47±3 km/s
Age390±61 Myr
Other designations
Merak, Mirak,[7] β Ursae Majoris, β UMa, Beta UMa, 48 Ursae Majoris, BD+57°1302, FK5 416, GC 15145, HD 95418, HIP 53910, HR 4295, PPM 32912, SAO 27876[8]
Database references
SIMBADdata
Size comparison between the Sun, Beta Ursae Majoris, Pollux, and Arcturus.

Merak /ˈmɪəræk/, also called Beta Ursae Majoris (β Ursae Majoris, abbreviated Beta UMa, β UMa),[9][10] is a star in the northern constellation of Ursa Major.

The apparent visual magnitude of this star is +2.37,[2] which means it is readily visible to the naked eye. It is more familiar to northern hemisphere observers as one of the "pointer stars" in the Big Dipper, or the Plough (UK), which is a prominent asterism of seven stars that forms part of the larger constellation. Extending an imaginary straight line from this star through the nearby Alpha Ursae Majoris (Dubhe) extends to Polaris, the north star.

Spectral classification

[edit]

In 1943, β Ursae Majoris was listed as a spectral standard for the class of A1 V.[11] When improved instruments made it possible to identify subgiant luminosity classes for early A-class stars, β Ursae Majoris was assigned that class A0 IV.[12] This was later revised to A1 IV.[3] It is considered to be a mild Am star, a type of chemically peculiar star with unusually strong lines of certain metallic elements.[13]

Properties

[edit]

Based upon parallax measurements, β Ursae Majoris is located at a distance of 79.7 light-years (24.4 parsecs) from the Sun. It is a subgiant, a star that has exhausted the hydrogen in its core and is now cooling as it generates energy through the thermonuclear fusion of hydrogen in a shell outside the core. The effective temperature of the outer envelope is about 9,225 K,[14] giving it a white-hued glow that is typical for A-type stars.[15] It is larger than the Sun, with about 2.7 times the mass and 2.84 times the solar radius. If they were viewed from the same distance, Beta Ursae Majoris would appear much brighter than the Sun, as it is radiating 68 times the Sun's luminosity.[14][16]

Observation of the star in the infrared reveal an excess emission that suggests the presence of a circumstellar debris disk of orbiting dust,[14] much like those discovered around Fomalhaut and Vega. The mean temperature of this disk is 120 K,[16] indicating that it is centered at a radius of 47 AU from the host star.[14] The dust has an estimated mass of about 0.27% the mass of the Earth.[16]

Beta Ursae Majoris is one of five stars in the Big Dipper that form a part of a loose open cluster called the Ursa Major moving group, sharing the same region of space and not just the same patch of sky from Earth's perspective. This group has an estimated age of about 500 (± 100) million years. As the members of this group share a common origin and motion through space, this yields an estimate for the age of Beta Ursae Majoris.[17] Two stars are known to be located in relatively close proximity: 37 Ursae Majoris at 5.2 light-years (1.6 pc) and Gamma Ursae Majoris at 11 light-years (3.4 pc); much closer to each other than these stars are to the Earth.[18]

Nomenclature

[edit]

β Ursae Majoris (Latinised to Beta Ursae Majoris) is the star's Bayer designation.

It bore the traditional name Merak derived from the Arabic المراق al-marāqq 'the loins' (of the bear).[7] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[19] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Merak for this star.[20]

The Hindus called the star Pulaha, one of the Seven Rishis.[7]

In Chinese, 北斗 (Běi Dǒu), meaning Northern Dipper, refers to an asterism equivalent to the Big Dipper. Consequently, the Chinese name for Beta Ursae Majoris itself is 北斗二 (Běi Dǒu èr, English: the Second Star of Northern Dipper) and 天璇 (Tiān Xuán, English: Star of Celestial Rotating Jade).[21]

In culture

[edit]

USS Merak (1918) and USS Merak (AF-21) are both United States navy ships.

See also

[edit]

References

[edit]
  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. S2CID 18759600.
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. ^ a b Phillips, N. M.; Greaves, J. S.; Dent, W. R. F.; Matthews, B. C.; Holland, W. S.; Wyatt, M. C.; Sibthorpe, B. (2010). "Target selection for the SUNS and DEBRIS surveys for debris discs in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 403 (3): 1089. arXiv:0911.3426. Bibcode:2010MNRAS.403.1089P. doi:10.1111/j.1365-2966.2009.15641.x. S2CID 119262858.
  4. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and Their Applications. Vol. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E.
  5. ^ Eggen, Olin J. (August 1998), "The Sirius Supercluster and Missing Mass near the Sun", The Astronomical Journal, 116 (2): 782–788, Bibcode:1998AJ....116..782E, doi:10.1086/300465.
  6. ^ Acharyya, A.; Aufdenberg, J. P.; Bangale, P.; Bartkoske, J. T.; Batista, P.; Benbow, W.; Chromey, A. J.; Davis, J. D.; Feng, Q.; Foote, G. M.; Furniss, A.; Hanlon, W.; Hinrichs, C. E.; Holder, J.; Jin, W. (2024-04-26). "An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory". The Astrophysical Journal. 966 (1): 28. arXiv:2401.01853. Bibcode:2024ApJ...966...28A. doi:10.3847/1538-4357/ad2b68. ISSN 0004-637X.
  7. ^ a b c Allen, Richard Hinckley (1899), "Star-names and their meanings", New York, G. E. Stechert: 438, Bibcode:1899sntm.book.....A
  8. ^ "MERAK -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-01
  9. ^ 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.
  10. ^ "IAU Catalog of Star Names". Retrieved 28 Apr 2019.
  11. ^ Morgan, William Wilson; Keenan, Philip Childs; Kellman, Edith (1943). "An atlas of stellar spectra, with an outline of spectral classification". Chicago. Bibcode:1943assw.book.....M.
  12. ^ Barry, Don C. (1970). "Spectral Classification of a and F Stars". The Astrophysical Journal Supplement Series. 19: 281. Bibcode:1970ApJS...19..281B. doi:10.1086/190209.
  13. ^ Renson, P.; Manfroid, J. (2009). "Catalogue of Ap, HGMN and Am stars". Astronomy and Astrophysics. 498 (3): 961. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788.
  14. ^ a b c d Wyatt, M. C.; et al. (July 2007), "Steady State Evolution of Debris Disks around A Stars", The Astrophysical Journal, 663 (1): 365–382, arXiv:astro-ph/0703608, Bibcode:2007ApJ...663..365W, doi:10.1086/518404, S2CID 18883195
  15. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
  16. ^ a b c Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID 11879505
  17. ^ Monier, R. (November 2005), "Abundances of a sample of A and F-type dwarf members of the Ursa Major Group", Astronomy and Astrophysics, 442 (2): 563–566, Bibcode:2005A&A...442..563M, doi:10.1051/0004-6361:20053222
  18. ^ Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement, 192 (1): 2, arXiv:1007.0425, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2, S2CID 119226823
  19. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  20. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  21. ^ (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
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