Polaris

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Alpha Ursae Minoris
Polaris alpha ursae minoris.jpg
Polaris as seen by the Hubble Space Telescope.
Observation data
Epoch J2000      Equinox
Constellation Ursa Minor
α UMi Aa
Richt ascension 02h 31m 49.09s
Declination +89° 15′ 50.8″
Apparent magnitude (V) 1.98v[1]
α UMi Ab
Richt ascension
Declination
Apparent magnitude (V) 9.2[1]
α UMi B
Richt ascension 02h 30m 41.63s
Declination +89° 15′ 38.1″
Apparent magnitude (V) 8.7[1]
Chairactereestics
α UMi Aa
Spectral type F7Ib[2]
U−B colour index 0.38[1]
B−V colour index 0.60[1]
Variable teep Classical Cepheid[3]
α UMi Ab
Spectral type F6V[1]
α UMi B
Spectral type F3V[1]
U−B colour index 0.01[4]
B−V colour index 0.42[4]
Astrometry
Radial velocity (Rv)-17 km/s
Proper motion (μ) RA: 44.48±0.11 mas/yr
Dec.: -11.85±0.13 mas/yr
Parallax (π)7.54 ± 0.11[5] mas
Distance323 - 433[6] ly
(99 - 133[6] pc)
Absolute magnitude (MV)-3.6(α UMi Aa)[1]
3.6(α UMi Ab)[1]
3.1(α UMi B)[1]
Orbit[1]
Primarα UMi Aa
Companionα UMi Ab
Period (P)29.59 yr
Semi-major axis (a)0.133″
Eccentricity (e)0.608
Inclination (i)128°
Longitude o the node (Ω)19°
Argument o periastron (ω)
(seicontar)
303°
Semi-amplitude (K1)
(primar)
3.72 km/s
Details
α UMi Aa
Mass5.4[7] M
Radius37.5[7] R
Luminosity (bolometric)1,260[7] L
Surface gravity (log g)2.2[8] cgs
Temperatur6015[4] K
Metallicity112% solar[9]
Rotation119 days[2]
Rotational velocity (v sin i)14[2] km/s
Age7×107[10] years
α UMi Ab
Mass1.26[1] M
Radius1.04[1] R
Luminosity (bolometric)3[1] L
Age7×107[10] years
α UMi B
Mass1.39[1] M
Radius1.38[4] R
Luminosity (bolometric)3.9[4] L
Surface gravity (log g)4.3[4] cgs
Temperatur6900[4] K
Rotational velocity (v sin i)110[4] km/s
Age7×107[10] years
Poseetion (relative tae α UMi Aa)
Componentα UMi Ab
Epoch o observation2005.5880
Angular distance0.172
Poseetion angle231.4°
Poseetion (relative tae α UMi Aa)
Componentα UMi B
Epoch o observation2005.5880
Angular distance18.217
Poseetion angle230.540°
Database references
α UMi Aa
SIMBADdata
α UMi B
SIMBADdata
Ither designations
Polaris, North Star, 1 Ursae Minoris, HR 424, BD +88°8, HD 8890, SAO 308, FK5 907, GC 2243, ADS 1477, CCDM 02319+8915, HIP 11767, Cynosura, Alruccabah, Phoenice, Navigatoria, Star of Arcady, Yilduz, Mismar

Polaris (α Ursae Minoris, α UMi, commonly the North Starn or Pole Starn) is the brichtest starn in the constellation Ursa Minor. It is very close tae the north celestial pole, makin it the current northren pole starn. The revised Hipparcos parallax gies a distance tae Polaris o aboot 433 licht-years (133 parsecs) while calculations bi ither methods derive distances aroond 30% closer.

References[eedit | eedit soorce]

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Evans, N. R.; Schaefer, G. H.; Bond, H. E.; Bono, G.; Karovska, M.; Nelan, E.; Sasselov, D.; Mason, B. D. (2008). "Direct Detection of the Close Companion of Polaris with Thehubble Space Telescope". The Astronomical Journal. 136 (3): 1137. arXiv:0806.4904Freely accessible. Bibcode:2008AJ....136.1137E. doi:10.1088/0004-6256/136/3/1137. 
  2. 2.0 2.1 2.2 Lee, B. C.; Mkrtichian, D. E.; Han, I.; Park, M. G.; Kim, K. M. (2008). "Precise Radial Velocities of Polaris: Detection of Amplitude Growth". The Astronomical Journal. 135 (6): 2240. arXiv:0804.2793Freely accessible. Bibcode:2008AJ....135.2240L. doi:10.1088/0004-6256/135/6/2240. 
  3. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S. 
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Usenko, I. A.; Klochkova, V. G. (2008). "Polaris B, an optical companion of the Polaris (α UMi) system: Atmospheric parameters, chemical composition, distance and mass". Monthly Notices of the Royal Astronomical Society: Letters. 387: L1. arXiv:0708.0333Freely accessible. Bibcode:2008MNRAS.387L...1U. doi:10.1111/j.1745-3933.2008.00426.x. 
  5. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  6. 6.0 6.1 Turner, D. G.; Kovtyukh, V. V.; Usenko, I. A.; Gorlova, N. I. (2013). "The Pulsation Mode of the Cepheid Polaris". The Astrophysical Journal Letters. 762: L8. arXiv:1211.6103Freely accessible. Bibcode:2013ApJ...762L...8T. doi:10.1088/2041-8205/762/1/L8. 
  7. 7.0 7.1 7.2 Fadeyev, Y. A. (2015). "Evolutionary status of Polaris". Monthly Notices of the Royal Astronomical Society. 449: 1011. arXiv:1502.06463Freely accessible. Bibcode:2015MNRAS.449.1011F. doi:10.1093/mnras/stv412. 
  8. Usenko, I. A.; Miroshnichenko, A. S.; Klochkova, V. G.; Yushkin, M. V. (2005). "Polaris, the nearest Cepheid in the Galaxy: Atmosphere parameters, reddening and chemical composition". Monthly Notices of the Royal Astronomical Society. 362 (4): 1219. Bibcode:2005MNRAS.362.1219U. doi:10.1111/j.1365-2966.2005.09353.x. 
  9. Cayrel de Strobel, G.; Soubiran, C.; Ralite, N. (2001). "Catalogue of [Fe/H] determinations for FGK stars: 2001 edition". Astronomy and Astrophysics. 373: 159. arXiv:astro-ph/0106438Freely accessible. Bibcode:2001A&A...373..159C. doi:10.1051/0004-6361:20010525. 
  10. 10.0 10.1 10.2 "Polaris: astrometric orbit, position, and proper motion". arXiv:astro-ph/0002406Freely accessible. Bibcode:2000A&A...360..399W. 

Coordinates: Sky map 02h 31m 48.7s, +89° 15′ 51″