Size comparison between the Sun, Beta Ursae Majoris, Pollux, and Arcturus.
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.
In 1943, β Ursae Majoris was listed as a spectral standard for the class of A1 V.[14] 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.[15] 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.[16]
PropertiesEdit
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,[6] giving it a white-hued glow that is typical for A-type stars.[17] 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.[6][18]
Observation of the star in the infrared reveal an excess emission that suggests the presence of a circumstellar debris disk of orbiting dust,[6] much like those discovered around Fomalhaut and Vega. The mean temperature of this disk is 120 K,[18] indicating that it is centered at a radius of 47 AU from the host star.[6] The dust has an estimated mass of about 0.27% the mass of the Earth.[18]
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.[8] 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.[19]
It bore the traditional name Merak derived from the Arabic المراق al-maraqq 'the loins' (of the bear).[10] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[20] 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.[21]
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).[22]
^ abcdevan 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.
^ abcdJohnson, 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
^ abPhillips, 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.
^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.
^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.
^ abcdeWyatt, 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
^ abcBoyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101, S2CID 18993744. See Table 10.
^ abcMonier, 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
^Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298
^ abcAllen, Richard Hinckley (1899), "Star-names and their meanings", New York, G. E. Stechert: 438, Bibcode:1899sntm.book.....A
^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. ISBN978-1-931559-44-7.
^"IAU Catalog of Star Names". Retrieved 28 Apr 2019.
^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.
^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.
^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.
^ abcRhee, 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
^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
^"IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
^"Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
^(in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日
beta, ursae, majoris, ursae, majoris, abbreviated, beta, formally, named, merak, ɪər, star, northern, constellation, ursa, major, merak, ursa, majorobservation, dataepoch, j2000, equinox, j2000, 0constellation, ursa, majorright, ascension, 47654s, declination,. Beta Ursae Majoris b Ursae Majoris abbreviated Beta UMa b UMa formally named Merak ˈ m ɪer ae k 12 13 is a star in the northern constellation of Ursa Major Beta Ursae MajorisMerak in Ursa MajorObservation dataEpoch J2000 0 Equinox J2000 0Constellation Ursa MajorRight ascension 11h 01m 50 47654s 1 Declination 56 22 56 7339 1 Apparent magnitude V 2 37 2 CharacteristicsSpectral type A1IVps 3 U B color index 0 00 2 B V color index 0 02 2 Variable type SuspectedAstrometryRadial velocity Rv 12 0 4 km sProper motion m RA 81 43 1 mas yr Dec 33 49 1 mas yrParallax p 40 90 0 16 mas 1 Distance79 7 0 3 ly 24 45 0 10 pc Absolute magnitude MV 0 61 5 DetailsMass2 7 6 M Radius3 021 0 038 7 R Luminosity63 015 1 307 7 L Surface gravity log g 3 83 8 cgsTemperature9377 75 7 KRotational velocity v sin i 46 9 km sAge500 100 8 MyrOther designationsMerak Mirak 10 b Ursae Majoris b UMa Beta UMa 48 Ursae Majoris BD 57 1302 FK5 416 GC 15145 HD 95418 HIP 53910 HR 4295 PPM 32912 SAO 27876 11 Database referencesSIMBADdataSize comparison between the Sun Beta Ursae Majoris Pollux and Arcturus 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 Contents 1 Spectral classification 2 Properties 3 Nomenclature 4 In culture 5 See also 6 ReferencesSpectral classification EditIn 1943 b Ursae Majoris was listed as a spectral standard for the class of A1 V 14 When improved instruments made it possible to identify subgiant luminosity classes for early A class stars b Ursae Majoris was assigned that class A0 IV 15 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 16 Properties EditBased upon parallax measurements b 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 6 giving it a white hued glow that is typical for A type stars 17 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 6 18 Observation of the star in the infrared reveal an excess emission that suggests the presence of a circumstellar debris disk of orbiting dust 6 much like those discovered around Fomalhaut and Vega The mean temperature of this disk is 120 K 18 indicating that it is centered at a radius of 47 AU from the host star 6 The dust has an estimated mass of about 0 27 the mass of the Earth 18 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 8 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 19 Nomenclature Editb 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 maraqq the loins of the bear 10 In 2016 the International Astronomical Union organized a Working Group on Star Names WGSN 20 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 21 The Hindus called the star Pulaha one of the Seven Rishis 10 In Chinese 北斗 Bei 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 Bei Dǒu er English the Second Star of Northern Dipper and 天璇 Tian Xuan English Star of Celestial Rotating Jade 22 In culture EditUSS Merak 1918 and USS Merak AF 21 are both United States navy ships See also EditLists of stars List of brightest stars List of nearest bright stars Historical brightest starsReferences Edit 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 amp A 474 653V doi 10 1051 0004 6361 20078357 S2CID 18759600 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 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 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 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 a b c d e 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 a b c Boyajian Tabetha S et al February 2012 Stellar Diameters and Temperatures I Main sequence A F and G Stars The Astrophysical Journal 746 1 101 arXiv 1112 3316 Bibcode 2012ApJ 746 101B doi 10 1088 0004 637X 746 1 101 S2CID 18993744 See Table 10 a b c 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 amp A 442 563M doi 10 1051 0004 6361 20053222 Royer F Zorec J Gomez A E February 2007 Rotational velocities of A type stars III Velocity distributions Astronomy and Astrophysics 463 2 671 682 arXiv astro ph 0610785 Bibcode 2007A amp A 463 671R doi 10 1051 0004 6361 20065224 S2CID 18475298 a b c Allen Richard Hinckley 1899 Star names and their meanings New York G E Stechert 438 Bibcode 1899sntm book A MERAK Variable Star SIMBAD Centre de Donnees astronomiques de Strasbourg retrieved 2012 01 01 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 IAU Catalog of Star Names Retrieved 28 Apr 2019 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 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 Renson P Manfroid J 2009 Catalogue of Ap HGMN and Am stars Astronomy and Astrophysics 498 3 961 Bibcode 2009A amp A 498 961R doi 10 1051 0004 6361 200810788 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 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 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 IAU Working Group on Star Names WGSN Retrieved 22 May 2016 Bulletin of the IAU Working Group on Star Names No 1 PDF Retrieved 28 July 2016 in Chinese AEEA Activities of Exhibition and Education in Astronomy 天文教育資訊網 2006 年 6 月 15 日 Portals nbsp Astronomy nbsp Stars nbsp Spaceflight nbsp Outer space nbsp Solar System Retrieved from https en wikipedia org w index php title Beta Ursae Majoris amp oldid 1156835330, wikipedia, wiki, book, books, library,
