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Alcor (star)

October 15, 2023

Alcor (/ˈælkɔːr/)[9] is a binary star system in the constellation of Ursa Major. It is the fainter companion of Mizar, the two stars forming a naked eye double in the handle of the Big Dipper (or Plough) asterism in Ursa Major. The two both lie about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite.

Alcor
Location of Alcor (Mizar is circled, Alcor is invisible beside it at this scale)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 13h 25m 13.53783s[1]
Declination +54° 59′ 16.6548″[1]
Apparent magnitude (V) +3.99[2]
Characteristics
Spectral type A5Vn[3] / M3-4[4]
Astrometry
Radial velocity (Rv)−9.6[5] km/s
Parallax (π)39.91 ± 0.13 mas[1]
Distance81.7 ± 0.3 ly
(25.06 ± 0.08 pc)
Absolute magnitude (MV)+2.00[2]
Details
Alcor A
Mass1.84[6] M☉
Radius1.846[7] R☉
Luminosity14.03[6] L☉
Surface gravity (log g)4.25[8] cgs
Temperature8,221[8] K
Rotational velocity (v sin i)228[6] km/s
Alcor B
Mass0.25[4] M☉
Age0.5 ± 0.1[2] Gyr
Other designations
g Ursae Majoris, 80 Ursae Majoris, BD+55 1603, CCDM J13240+5456D, GC 18155, HD 116842, HIP 65477, HR 5062, PPM 34021, SAO 28751, WDS J13239+5456C
Database references
SIMBADdata

Nomenclature Edit

Alcor has the Flamsteed designation 80 Ursae Majoris. Alcor derives from Arabic الخوار al-khawāri, meaning 'faint one';[10][11][12] notable as a faintly perceptible companion of Mizar.[13]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[15] included a table of the first two batches of names approved by the WGSN; which included Alcor for 80 UMa.[16]

Mizar and Alcor Edit

Main article: Mizar and Alcor
 
Mizar and Alcor in constellation Ursa Major

With normal eyesight Alcor appears at about 12 minutes of arc from the second-magnitude star Mizar. Alcor is of magnitude 3.99 and spectral class A5V.

Mizar's and Alcor's proper motions show they move together, along with most of the other stars of the Big Dipper except Dubhe and Alkaid, as members of the Ursa Major Moving Group, a mostly dispersed group of stars sharing a common birth. However, it has yet to be demonstrated conclusively that they are gravitationally bound. Recent studies indicate that Alcor and Mizar are somewhat closer together than previously thought: approximately 74,000 ± 39,000 AU, or 0.5–1.5 light-years. The uncertainty is due to our uncertainty about the exact distances from us. If they are exactly the same distance from us (somewhat unlikely) then the distance between them is only 17,800 AU (0.281 light-years).[2]

Alcor B Edit

 
The Big Dipper's bowl and part of the handle photographed from the International Space Station. Mizar and Alcor are at the upper right.

In 2009, Alcor was discovered to have a companion star Alcor B, a magnitude 8.8 red dwarf.[17]

Alcor B was discovered independently by two groups. One group led by Eric Mamajek (University of Rochester) and colleagues at Steward Observatory University of Arizona used adaptive optics on the 6.5-meter telescope at MMT Observatory. Another led by Neil Zimmerman, a graduate student at Columbia University and member of Project 1640, an international collaborative team that includes astrophysicists at the American Museum of Natural History, the University of Cambridge's Institute of Astronomy, the California Institute of Technology, and NASA's Jet Propulsion Laboratory, used the 5-meter Hale Telescope at Palomar Observatory.[4]

Alcor B is one second of arc away from Alcor A.[4] Its spectral type is M3-4 and it is a main-sequence star, a red dwarf.

Alcor A and B are situated 1.2 light-years away from, and are co-moving with, the Mizar quadruple system, making the system the second-closest stellar sextuplet—only Castor is closer.[18] The Mizar–Alcor stellar sextuple system belongs to the Ursa Major Moving Group, a stellar group of stars of similar ages and velocities,[2] and the closest cluster-like object to Earth.

Other names Edit

In Arabic, Alcor is also known as Al-Sahja (the rhythmical form of the usual al-Suhā) meaning 'forgotten', 'lost', or 'neglected'.[19]

In traditional Indian astronomy,[20] Alcor was known as Arundhati, wife of one of the Saptarishi.

In the Miꞌkmaq myth of the great bear and the seven hunters,[21] Mizar is Chickadee and Alcor is his cooking pot.

Military namesakes Edit

USS Alcor (AD-34) and USS Alcor (AK-259) are both United States Navy ships.

References Edit

  1. ^ a b c 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 e Mamajek, Eric E.; Kenworthy, Matthew A.; Hinz, Philip M.; Meyer, Michael R. (2010). "Discovery of a Faint Companion to Alcor Using MMT/AO 5 μm Imaging". The Astronomical Journal. 139 (3): 919–925. arXiv:0911.5028. Bibcode:2010AJ....139..919M. doi:10.1088/0004-6256/139/3/919. S2CID 51834159.
  3. ^ Gray, R. O; Garrison, R. F (1989). "The late A-type stars - Refined MK classification, confrontation with Stromgren photometry, and the effects of rotation". Astrophysical Journal Supplement Series. 70: 623. Bibcode:1989ApJS...70..623G. doi:10.1086/191349.
  4. ^ a b c d Zimmerman, Neil; Oppenheimer, Ben R; Hinkley, Sasha; Brenner, Douglas; Parry, Ian R; Sivaramakrishnan, Anand; Hillenbrand, Lynne; Beichman, Charles; Crepp, Justin R; Vasisht, Gautam; Roberts, Lewis C; Burruss, Rick; King, David L; Soummer, Rémi; Dekany, Richard; Shao, Michael; Bouchez, Antonin; Roberts, Jennifer E; Hunt, Stephanie (2010). "Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor". The Astrophysical Journal. 709 (2): 733–740. arXiv:0912.1597. Bibcode:2010ApJ...709..733Z. doi:10.1088/0004-637X/709/2/733. S2CID 6052794.
  5. ^ Kidger, Mark R; Martín-Luis, Fabiola (2003). "High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere". The Astronomical Journal. 125 (6): 3311. Bibcode:2003AJ....125.3311K. doi:10.1086/374996.
  6. ^ a b c Zorec, J; Royer, F (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. S2CID 55586789.
  7. ^ Jones, Jeremy; White, R. J; Boyajian, T; Schaefer, G; Baines, E; Ireland, M; Patience, J; Ten Brummelaar, T; McAlister, H; Ridgway, S. T; Sturmann, J; Sturmann, L; Turner, N; Farrington, C; Goldfinger, P. J (2015). "The Ages of A-Stars. I. Interferometric Observations and Age Estimates for Stars in the Ursa Major Moving Group". The Astrophysical Journal. 813 (1): 58. arXiv:1508.05643. Bibcode:2015ApJ...813...58J. doi:10.1088/0004-637X/813/1/58. S2CID 16600591.
  8. ^ a b David, Trevor J; Hillenbrand, Lynne A (2015). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. S2CID 33401607.
  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. ^ "Britannica - Alcor". 2009-12-21. Retrieved 2022-12-29.
  11. ^ "Backyardbend - From Alcor to Zappafrank: How the Stars and Other Celestial Objects Got Their Names". 2021-05-30. Retrieved 2022-12-29.
  12. ^ List of Arabic star names, published in Popular Astronomy, January 1895, by Professor Robert H. West, of the Syrian Protestant College at Beirut.
  13. ^ Bohigian, George M. (2008). "An Ancient Eye Test—Using the Stars". Survey of Ophthalmology. 53 (5): 536–9. doi:10.1016/j.survophthal.2008.06.009. PMID 18929764.
  14. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  15. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  16. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  17. ^ Science, SPACE com Staff 2009-12-10T02:16:00Z; Astronomy (10 December 2009). "New Star Found in Big Dipper". Space.com. Retrieved 2019-10-30.
  18. ^ Dan Vergano (December 11, 2009). "Two Big Dipper constellation stars actually six". USA Today. Retrieved 2019-10-30.
  19. ^ "Constellations of words - Alcor". Retrieved 2022-12-29.
  20. ^ V.Chandran (1993-01-01). Astronomy Quiz Book. Pustak Mahal, 1993. ISBN 978-81-223-0366-7. ... the seven rishis in the constellation Saptarishi (Ursa Major) ... In Vasishta (Zeta), its tiny companion star is named after Arundhati, the wife of Vasishta ... today known by their Arabic names Dubhe (Kratu), Merak (Pulaha), Phekda (Pulastya), Megrez (Atri), Benetnash (Marichi) and Mizar (Vasishta) ...
  21. ^ . 2009-02-11. Archived from the original on 2017-10-18. Retrieved 2018-01-01.

External links Edit

  • Alcor at Jim Kaler's Stars website
  • Alcor (star) on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

October 15, 2023
alcor, star, alcor, ɔːr, binary, star, system, constellation, ursa, major, fainter, companion, mizar, stars, forming, naked, double, handle, dipper, plough, asterism, ursa, major, both, about, light, years, away, from, measured, hipparcos, astrometry, satellit. Alcor ˈ ae l k ɔːr 9 is a binary star system in the constellation of Ursa Major It is the fainter companion of Mizar the two stars forming a naked eye double in the handle of the Big Dipper or Plough asterism in Ursa Major The two both lie about 83 light years away from the Sun as measured by the Hipparcos astrometry satellite AlcorLocation of Alcor Mizar is circled Alcor is invisible beside it at this scale Observation dataEpoch J2000 0 Equinox J2000 0Constellation Ursa MajorRight ascension 13h 25m 13 53783s 1 Declination 54 59 16 6548 1 Apparent magnitude V 3 99 2 CharacteristicsSpectral type A5Vn 3 M3 4 4 AstrometryRadial velocity Rv 9 6 5 km sParallax p 39 91 0 13 mas 1 Distance81 7 0 3 ly 25 06 0 08 pc Absolute magnitude MV 2 00 2 DetailsAlcor AMass1 84 6 M Radius1 846 7 R Luminosity14 03 6 L Surface gravity log g 4 25 8 cgsTemperature8 221 8 KRotational velocity v sin i 228 6 km sAlcor BMass0 25 4 M Age0 5 0 1 2 GyrOther designationsg Ursae Majoris 80 Ursae Majoris BD 55 1603 CCDM J13240 5456D GC 18155 HD 116842 HIP 65477 HR 5062 PPM 34021 SAO 28751 WDS J13239 5456CDatabase referencesSIMBADdata Contents 1 Nomenclature 2 Mizar and Alcor 3 Alcor B 4 Other names 5 Military namesakes 6 References 7 External linksNomenclature EditAlcor has the Flamsteed designation 80 Ursae Majoris Alcor derives from Arabic الخوار al khawari meaning faint one 10 11 12 notable as a faintly perceptible companion of Mizar 13 In 2016 the International Astronomical Union organized a Working Group on Star Names WGSN 14 to catalog and standardize proper names for stars The WGSN s first bulletin of July 2016 15 included a table of the first two batches of names approved by the WGSN which included Alcor for 80 UMa 16 Mizar and Alcor EditMain article Mizar and Alcor nbsp Mizar and Alcor in constellation Ursa MajorWith normal eyesight Alcor appears at about 12 minutes of arc from the second magnitude star Mizar Alcor is of magnitude 3 99 and spectral class A5V Mizar s and Alcor s proper motions show they move together along with most of the other stars of the Big Dipper except Dubhe and Alkaid as members of the Ursa Major Moving Group a mostly dispersed group of stars sharing a common birth However it has yet to be demonstrated conclusively that they are gravitationally bound Recent studies indicate that Alcor and Mizar are somewhat closer together than previously thought approximately 74 000 39 000 AU or 0 5 1 5 light years The uncertainty is due to our uncertainty about the exact distances from us If they are exactly the same distance from us somewhat unlikely then the distance between them is only 17 800 AU 0 281 light years 2 Alcor B Edit nbsp The Big Dipper s bowl and part of the handle photographed from the International Space Station Mizar and Alcor are at the upper right In 2009 Alcor was discovered to have a companion star Alcor B a magnitude 8 8 red dwarf 17 Alcor B was discovered independently by two groups One group led by Eric Mamajek University of Rochester and colleagues at Steward Observatory University of Arizona used adaptive optics on the 6 5 meter telescope at MMT Observatory Another led by Neil Zimmerman a graduate student at Columbia University and member of Project 1640 an international collaborative team that includes astrophysicists at the American Museum of Natural History the University of Cambridge s Institute of Astronomy the California Institute of Technology and NASA s Jet Propulsion Laboratory used the 5 meter Hale Telescope at Palomar Observatory 4 Alcor B is one second of arc away from Alcor A 4 Its spectral type is M3 4 and it is a main sequence star a red dwarf Alcor A and B are situated 1 2 light years away from and are co moving with the Mizar quadruple system making the system the second closest stellar sextuplet only Castor is closer 18 The Mizar Alcor stellar sextuple system belongs to the Ursa Major Moving Group a stellar group of stars of similar ages and velocities 2 and the closest cluster like object to Earth Other names EditIn Arabic Alcor is also known as Al Sahja the rhythmical form of the usual al Suha meaning forgotten lost or neglected 19 In traditional Indian astronomy 20 Alcor was known as Arundhati wife of one of the Saptarishi In the Miꞌkmaq myth of the great bear and the seven hunters 21 Mizar is Chickadee and Alcor is his cooking pot Military namesakes EditUSS Alcor AD 34 and USS Alcor AK 259 are both United States Navy ships References Edit a b c 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 e Mamajek Eric E Kenworthy Matthew A Hinz Philip M Meyer Michael R 2010 Discovery of a Faint Companion to Alcor Using MMT AO 5 mm Imaging The Astronomical Journal 139 3 919 925 arXiv 0911 5028 Bibcode 2010AJ 139 919M doi 10 1088 0004 6256 139 3 919 S2CID 51834159 Gray R O Garrison R F 1989 The late A type stars Refined MK classification confrontation with Stromgren photometry and the effects of rotation Astrophysical Journal Supplement Series 70 623 Bibcode 1989ApJS 70 623G doi 10 1086 191349 a b c d Zimmerman Neil Oppenheimer Ben R Hinkley Sasha Brenner Douglas Parry Ian R Sivaramakrishnan Anand Hillenbrand Lynne Beichman Charles Crepp Justin R Vasisht Gautam Roberts Lewis C Burruss Rick King David L Soummer Remi Dekany Richard Shao Michael Bouchez Antonin Roberts Jennifer E Hunt Stephanie 2010 Parallactic Motion for Companion Discovery An M Dwarf Orbiting Alcor The Astrophysical Journal 709 2 733 740 arXiv 0912 1597 Bibcode 2010ApJ 709 733Z doi 10 1088 0004 637X 709 2 733 S2CID 6052794 Kidger Mark R Martin Luis Fabiola 2003 High Precision Near Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere The Astronomical Journal 125 6 3311 Bibcode 2003AJ 125 3311K doi 10 1086 374996 a b c Zorec J Royer F 2012 Rotational velocities of A type stars IV Evolution of rotational velocities Astronomy amp Astrophysics 537 A120 arXiv 1201 2052 Bibcode 2012A amp A 537A 120Z doi 10 1051 0004 6361 201117691 S2CID 55586789 Jones Jeremy White R J Boyajian T Schaefer G Baines E Ireland M Patience J Ten Brummelaar T McAlister H Ridgway S T Sturmann J Sturmann L Turner N Farrington C Goldfinger P J 2015 The Ages of A Stars I Interferometric Observations and Age Estimates for Stars in the Ursa Major Moving Group The Astrophysical Journal 813 1 58 arXiv 1508 05643 Bibcode 2015ApJ 813 58J doi 10 1088 0004 637X 813 1 58 S2CID 16600591 a b David Trevor J Hillenbrand Lynne A 2015 The Ages of Early type Stars Stromgren Photometric Methods Calibrated Validated Tested and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets The Astrophysical Journal 804 2 146 arXiv 1501 03154 Bibcode 2015ApJ 804 146D doi 10 1088 0004 637X 804 2 146 S2CID 33401607 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 Britannica Alcor 2009 12 21 Retrieved 2022 12 29 Backyardbend From Alcor to Zappafrank How the Stars and Other Celestial Objects Got Their Names 2021 05 30 Retrieved 2022 12 29 List of Arabic star names published in Popular Astronomy January 1895 by Professor Robert H West of the Syrian Protestant College at Beirut Bohigian George M 2008 An Ancient Eye Test Using the Stars Survey of Ophthalmology 53 5 536 9 doi 10 1016 j survophthal 2008 06 009 PMID 18929764 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 IAU Catalog of Star Names Retrieved 28 July 2016 Science SPACE com Staff 2009 12 10T02 16 00Z Astronomy 10 December 2009 New Star Found in Big Dipper Space com Retrieved 2019 10 30 Dan Vergano December 11 2009 Two Big Dipper constellation stars actually six USA Today Retrieved 2019 10 30 Constellations of words Alcor Retrieved 2022 12 29 V Chandran 1993 01 01 Astronomy Quiz Book Pustak Mahal 1993 ISBN 978 81 223 0366 7 the seven rishis in the constellation Saptarishi Ursa Major In Vasishta Zeta its tiny companion star is named after Arundhati the wife of Vasishta today known by their Arabic names Dubhe Kratu Merak Pulaha Phekda Pulastya Megrez Atri Benetnash Marichi and Mizar Vasishta The Celestial Bear A Micmac Legend 2009 02 11 Archived from the original on 2017 10 18 Retrieved 2018 01 01 External links EditAlcor at Jim Kaler s Stars website Alcor star on WikiSky DSS2 SDSS GALEX IRAS Hydrogen a X Ray Astrophoto Sky Map Articles and images Retrieved from https en wikipedia org w index php title Alcor star amp oldid 1170259809, wikipedia, wiki, book, books, library,

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