2 Ursae Minoris

2 Ursae Minoris (2 UMi) is a single[9] star a few degrees away from the northern celestial pole. Despite its Flamsteed designation, the star is actually located in the constellation Cepheus. This changed occurred when the constellation boundaries were formally set in 1930 by Eugene Delporte. Therefore, the star is usually referred only by its catalog numbers such as HR 285 or HD 5848. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.244.[2] This object is located 280 light years away and is moving further from the Earth with a heliocentric radial velocity of +8 km/s.[5] It is a candidate member of the Hyades Supercluster.[2]

2 Ursae Minoris
Observation data
Epoch J2000      Equinox J2000
Constellation Cepheus
Right ascension  01h 08m 44.88005s[1]
Declination 86° 15′ 25.5240″[1]
Apparent magnitude (V) 4.244[2]
Characteristics
Spectral type K2 II-III[3]
B−V color index 1.213±0.012[4]
Astrometry
Radial velocity (Rv)+8.36±0.19[5] km/s
Proper motion (μ) RA: 80.65±0.16[1] mas/yr
Dec.: −11.54±0.17[1] mas/yr
Parallax (π)11.64 ± 0.15[1] mas
Distance280 ± 4 ly
(86 ± 1 pc)
Absolute magnitude (MV)−0.43[4]
Details
Mass2.27±0.41[6] M☉
Radius24.00+1.15
−0.85[5] R☉
Luminosity215.097±6.132[5] L☉
Surface gravity (log g)2.48±0.17[2] cgs
Temperature4,512.5+62.2
−105.0[5] K
Metallicity [Fe/H]0.068±0.010[2] dex
Rotational velocity (v sin i)1.0[7] km/s
Other designations
2 UMi, BD+85°19, FK5 906, HD 5848, HIP 5372, HR 285, SAO 181[8]
Database references
SIMBADdata

This is an aging K-type star with a stellar classification of K2 II-III,[3] showing a luminosity class with blended traits of a giant and a bright giant. It has 2.3[6] times the mass of the Sun and has expanded to 24[5] times the Sun's radius. The star is radiating around 215[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,513 K.[5]

References
  1. 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.
  2. Tabernero, H. M.; Montes, D.; González Hernández, J. I. (November 2012), "Chemically tagging the Hyades Supercluster. A homogeneous sample of F6-K4 kinematically selected northern stars", Astronomy & Astrophysics, 547: 15, arXiv:1205.4879, Bibcode:2012A&A...547A..13T, doi:10.1051/0004-6361/201117506, A13.
  3. Eggen, O. J. (1962), "Space-velocity vectors for 3483 stars with proper motion and radial velocity", Royal Observatory Bulletin, 51, Bibcode:1962RGOB...51...79E.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  6. Stello, D.; et al. (2008), "Oscillating K Giants with the WIRE Satellite: Determination of Their Asteroseismic Masses", The Astrophysical Journal Letters, 674 (1): L53–L56, arXiv:0801.2155, Bibcode:2008ApJ...674L..53S, doi:10.1086/528936.
  7. Lèbre, A.; et al. (May 2006), "Lithium abundances and rotational behavior for bright giant stars", Astronomy and Astrophysics, 450 (3): 1173–1179, Bibcode:2006A&A...450.1173L, doi:10.1051/0004-6361:20053485.
  8. "HD 5848". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-01-04.
  9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
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