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Mízar (ζ UMa, ζ Ursae Majoris, Zeta Ursae Majoris) je zvezda v ozvezdju Velikega medveda (Ursa Major), srednja zvezda ojesa Velikega voza. Ime Mizar izvira iz arabščine ميزر mīzar in pomeni pas.

Mizar
Ursa Major constellation map.svg
Red circle.svg
Lega Mizarja (obkroženo)
Opazovalni podatki
Epoha J2000      Enakonočje J2000
Ozvezdje Veliki medved
Mizar
Rektascenzija 13h 23m 55,54048s[1]
Deklinacija +54° 55′ 31,2671″[1]
Navidezni sij (V) 2,04[2]
ζ1 UMa
Rektascenzija 13h 23m 55,543s[3]
Deklinacija +54° 55′ 31,30″[3]
Navidezni sij (V) 2,23[3]
ζ2 UMa
Rektascenzija 13h 23m 56,330s[3]
Deklinacija +54° 55′ 18,56″[3]
Navidezni sij (V) 3,88[3]
Značilnosti
ζ1 UMa
Spektralni razred A2Vp/A2Vp[4]
U−B Barvni indeks −0,01[5]
B−V Barvni indeks +0,02[5]
ζ2 UMa
Spektralni razred kA1h(eA)mA7IV-V[6]
U−B Barvni indeks +0,09[5]
B−V Barvni indeks +0,13[5]
Astrometrija
Radialna hitrost (Rv)−6,31[7] km/s
Lastno gibanje (μ)RA: 119,01[1] mas/l
Dec.: −25,97[1] mas/l
Paralaksa (π)39,36 ± 0,30[8] mas
Oddaljenost82.9 ± 0.6 sv. l.
(25.4 ± 0.2 pc)
Absolutni izsev (MV)+0,32/+1,96[9]
Orbita
PrimarnaMizar Aa
SpremljevalkaMizar Ab
Perioda (P)20,5386 days[10]
Glavna polos (a)9,83±0,03[11] mas
Izsrednost tira (e)0,5415±0,0016[10]
Naklon tira (i)60,5±0,3[10]°
Dolžina vozla (Ω)106,0±0,4[11]°
Epoha periastrona (T)RJD 54536,9904[10]
Argument periastrona (ω)
(sekundarni)
105,27±0,23[10]°
Pol-amplituda (K1)
(Argument periastrona)
66,478±0,153[10] km/s
Pol-amplituda (K2)
(sekundarni)
66,019±0,177[10] km/s
Orbita
PrimarnaMizar Ba
SpremljevalkaMizar Bb
Perioda (P)175,55[12]
Glavna polos (a)29,849 mas
Izsrednost tira (e)0,46[12]
Podrobnosti
Mizar Aa
Masa2,2224±0,0221[10] M
Polmer2,4 ± 0,1[11] R
Izsev33,3 ± 2,1[11] L
Temperatura9.000 ± 200[11] K
Starost370[13] Ma
Mizar Ab
Masa2,2381±0,0219[10] M
Polmer2,4 ± 0,1[11] R
Izsev33,3 ± 2,1[11] L
Temperatura9.000 ± 200[11] K
ζ2 UMa
Površinska težnost (log g)4,40[14] cgs
Temperatura8.425[14] K
Tirna hitrost(v sin i)61[14] km/s
Druge oznake
ζ Ursae Majoris, ζ UMa, Zeta UMa, 79 Ursae Majoris, BD+55 1598, CCDM J13240+5456, HIP 65378, WDS J13239+5456
ζ1 UMa: GC 18133, HD 116656, HR 5054, PPM 34007, SAO 28737
ζ2 UMa: GC 18134, HD 116657, HR 5055, SAO 28738
Sklici na podatkovne baze
SIMBADMizar
1 UMa
2 UMa
Lega Mizarja v ozvezdju Velikega medveda

Mizar ima navidezni sij 2,40m in spektralni razred A1 V.

V bližini Mizarja se nahaja temnejša zvezda Alkor, ki ima magnitudo 4,02m. Razločevanje teh dveh zvezd z golim očesom je bil dolgo časa preskus dobrega vida. Trenutno še ni natančno znano ali zvezdi tvorita pravo dvozvezdje ali sta le navidezno tesno skupaj.

SkliciUredi

  1. 1,0 1,1 1,2 1,3 van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. Bibcode:2007A&A...474..653V. arXiv:0708.1752. doi:10.1051/0004-6361:20078357. 
  2. Mermilliod, J.-C (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M. 
  3. 3,0 3,1 3,2 3,3 3,4 3,5 Fabricius, C; Høg, E; Makarov, V. V; Mason, B. D; Wycoff, G. L; Urban, S. E (2002). "The Tycho double star catalogue". Astronomy and Astrophysics 384: 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822. 
  4. Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society 389 (2): 869–879. Bibcode:2008MNRAS.389..869E. arXiv:0806.2878. doi:10.1111/j.1365-2966.2008.13596.x. 
  5. 5,0 5,1 5,2 5,3 Iriarte, Braulio; Johnson, Harold L; Mitchell, Richard I; Wisniewski, Wieslaw K (1965). "Five-Color Photometry of Bright Stars". Sky and Telescope 30: 21. Bibcode:1965S&T....30...21I. 
  6. Gray, R. O; Garrison, R. F (1987). "The early a type stars - Refined MK classification, confrontation with Stroemgren photometry, and the effects of rotation". Astrophysical Journal Supplement Series 65: 581. Bibcode:1987ApJS...65..581G. doi:10.1086/191237. 
  7. Pourbaix, D; Tokovinin, A. A; Batten, A. H; Fekel, F. C; Hartkopf, W. I; Levato, H; Morrell, N. I; Torres, G; Udry, S (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics 424 (2): 727–732. Bibcode:2004A&A...424..727P. arXiv:astro-ph/0406573. doi:10.1051/0004-6361:20041213. 
  8. 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. Bibcode:2010AJ....139..919M. arXiv:0911.5028. doi:10.1088/0004-6256/139/3/919. 
  9. King, Jeremy R; Villarreal, Adam R; Soderblom, David R; Gulliver, Austin F; Adelman, Saul J (2003). "Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group". The Astronomical Journal 125 (4): 1980. Bibcode:2003AJ....125.1980K. doi:10.1086/368241. 
  10. 10,0 10,1 10,2 10,3 10,4 10,5 10,6 10,7 10,8 Behr, Bradford B; Cenko, Andrew T; Hajian, Arsen R; McMillan, Robert S; Murison, Marc; Meade, Jeff; Hindsley, Robert (2011). "Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. II. Orbits of Double-lined Spectroscopic Binaries". The Astronomical Journal 142 (1): 6. Bibcode:2011AJ....142....6B. arXiv:1104.1447. doi:10.1088/0004-6256/142/1/6. 
  11. 11,0 11,1 11,2 11,3 11,4 11,5 11,6 11,7 Hummel, C. A.; Mozurkewich, D.; Armstrong, J. T.; Hajian, Arsen R.; Elias Ii, N. M.; Hutter, D. J. (1998). "Navy Prototype Optical Interferometer Observations of the Double Stars Mizar a and Matar". The Astronomical Journal 116 (5): 2536. Bibcode:1998AJ....116.2536H. doi:10.1086/300602. 
  12. 12,0 12,1 Iliev, I. Kh; Budaj, J; Zverko, J; Barzova, I. S; Ziznovsky, J (1998). "Lithium and metal abundances in long period AM binaries". Astronomy and Astrophysics Supplement 128 (3): 497. Bibcode:1998A&AS..128..497I. doi:10.1051/aas:1998160. 
  13. Thureau, N. D; Greaves, J. S; Matthews, B. C; Kennedy, G; Phillips, N; Booth, M; Duchêne, G; Horner, J; Rodriguez, D. R; Sibthorpe, B; Wyatt, M. C (2014). "An unbiased study of debris discs around A-type stars with Herschel". Monthly Notices of the Royal Astronomical Society 445 (3): 2558. Bibcode:2014MNRAS.445.2558T. doi:10.1093/mnras/stu1864. 
  14. 14,0 14,1 14,2 Monier, R (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. 

Koordinati:   13h 23m 55.5s, +54° 55′ 31″