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W Ursae Minoris
A visual band light curve for W Ursae Minoris, adapted from Devinney et al. (1970) [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Ursa Minor
Right ascension 16h 08m 27.2728s [2]
Declination +86° 11′ 59.5511″ [2]
Apparent magnitude (V) 8.51-9.59 [3]
Spectral type A1/2V [4] (A3V + G2IV) [5]
Variable type Algol [3]
Radial velocity (Rv)−15.3±1.1 [6] km/s
Proper motion (μ) RA: −12.128±0.057 [2]  mas/ yr
Dec.: 15.934±0.058 [2]  mas/ yr
Parallax (π)2.4144 ± 0.0315  mas [2]
Distance1,350 ± 20  ly
(414 ± 5  pc)
Orbit [6]
Period (P)1.7 days
Semi-major axis (a)10.01±0.06  R
Eccentricity (e)0
Inclination (i)83.57±0.18°
Semi-amplitude (K1)
90.4±1.5 km/s
Semi-amplitude (K2)
196.6±2.6 km/s
Details [6]
Mass3.22±0.08  M
Radius9.63±0.04  R
Luminosity89±6  L
Surface gravity (log g)3.83±0.02  cgs
Temperature9,310±90  K
Mass1.44±0.05  M
Radius3.09±0.03  R
Surface gravity (log g)3.62±0.02  cgs
Temperature5,240±200  K
Age≈400  Myr
Other designations
HD 150265, HIP 79069, SAO 2692 [7]
Database references

W Ursae Minoris is an eclipsing binary star system in the constellation Ursa Minor. Its apparent magnitude ranges from 8.51 to 9.59 over 1.7 days as one star passes in front of the other relative to observers on Earth. [3] The combined spectrum of the system is A1/2V.

Slight changes in the orbital period suggest that there is a third component of the multiple star system, most likely a red dwarf, with an orbital period of 62.2±3.9 years. [8] Another study suggests that the third star has a minimum mass of 0.49 M and an orbit of about 72 years. [6]

The two main stars are currently thought to have masses of 3.2  M and 1.4 M respectively. Models of their evolution and mass transfer suggest that the secondary star was initially the more massive of the two and that it has lost mass to what is now the primary as well as losing mass completely from the system. The two stars have also spiralled in towards each other over the few hundred million years since they formed. [6]


  1. ^ Devinney, Edward J.; Hall, Douglas S.; Ward, David H. (February 1970). "Two Independent Photoelectric Light Curves and Solutions of W Ursae Minoris". Publications of the Astronomical Society of the Pacific. 82 (484). Bibcode: 1970PASP...82...10D. doi: 10.1086/128884.
  2. ^ a b c d e 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.
  3. ^ a b c Watson, Christopher (4 January 2010). "W Ursae Minoris". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 July 2015.
  4. ^ Hill, G.; et al. (1975). "MK Classifications of some Northern Hemisphere Binary Systems". Memoirs of the Royal Astronomical Society. 79: 131. Bibcode: 1975MmRAS..79..131H.
  5. ^ Malkov, Oleg Yu (February 2020). "Semidetached double-lined eclipsing binaries: Stellar parameters and rare classes". Monthly Notices of the Royal Astronomical Society. 491 (4): 5489–5497. Bibcode: 2020MNRAS.491.5489M. doi: 10.1093/mnras/stz3363.
  6. ^ a b c d e Soydugan, Faruk; Soydugan, Esin; Aliçavuş, Fahri (2020). "Investigation of near-contact semi-detached binary WUMi through observations and evolutionary models". Research in Astronomy and Astrophysics. 20 (4): 052. arXiv: 1912.03664. Bibcode: 2020RAA....20...52S. doi: 10.1088/1674-4527/20/4/52. S2CID  208920968.
  7. ^ "W UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-07.
  8. ^ Kreiner, J. M.; Pribulla, T.; Tremko, J.; Stachowski, G. S.; Zakrzewski, B. (2008). "Period analysis of three close binary systems: TW And, TT Her and W UMi". Monthly Notices of the Royal Astronomical Society. 383 (4): 1506–12. Bibcode: 2008MNRAS.383.1506K. doi: 10.1111/j.1365-2966.2007.12652.x.