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Pi2 Ursae Minoris
Observation data
Epoch J2000       Equinox J2000
Constellation Ursa Minor
Right ascension 15h 39m 38.61131s [1]
Declination +79° 58′ 59.5495″ [1]
Apparent magnitude (V) 6.89 [2] (7.32 + 8.15) [3]
Spectral type F1V [4] + G0 [5]
B−V color index 0.392±0.015 [2]
Radial velocity (Rv)−32.10±1.8 [6] km/s
Proper motion (μ) RA: −32.643 [1]  mas/ yr
Dec.: 41.425 [1]  mas/ yr
Parallax (π)8.1090 ± 0.2844  mas [1]
Distance400 ± 10  ly
(123 ± 4  pc)
Absolute magnitude (MV)1.69±0.08 [6]
Orbit [5]
Period (P)171.62±8.68 yr
Semi-major axis (a)0.464±0.083
Eccentricity (e)0.961±0.014
Inclination (i)135.2±10.5°
Longitude of the node (Ω)123.4±32.6°
Periastron epoch (T)1904.15±2.89
Argument of periastron (ω)
Mass1.87 [7]  M
[1]  R
Luminosity16.5±0.7 [1]  L
Temperature6,858±80 [7]  K
Metallicity [Fe/H]+0.09 [7]  dex
Age1.20 [7]  Gyr
Other designations
π2 UMi, 18 Ursae Minoris, BD+80°487, HD 141652, HIP 76695, SAO 2588, WDS J15396+7959AB [8]
Database references

Pi2 Ursae Minoris, which is Latinized from π2 UMi Ursae Minoris, is a binary star system in the northern circumpolar constellation of Ursa Minor. The pair have a combined apparent visual magnitude of 6.89, [2] which can be viewed with a pair of binoculars. [9] They are located at a distance of approximately 400  light years from the Sun based on parallax, but are drifting closer with a radial velocity of −32 km/s. [6]

This star was found to be a double system by O. Struve in 1832, and the pair have now completed a full orbit. There is a lot of scatter in the data though, [5] so the grade of the orbital elements is rated as poor. [3] The system has a high eccentricity of 0.96 and they orbit each other with a period of roughly 172 years. [5] The magnitude 7.32 primary is an F-type main-sequence star with a stellar classification of F1V. [4] The fainter secondary has a magnitude of 8.15 [3] and is G-type star. [5] At present the angular separation between both stars is 0.67 arcseconds [1].


  1. ^ a b c d e f g 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.
  2. ^ a b c 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. S2CID  119257644.
  3. ^ a b c Malkov, O. Yu.; et al. (2012). "Dynamical Masses of a Selected Sample of Orbital Binaries". Astronomy & Astrophysics. 546: 5. Bibcode: 2012A&A...546A..69M. doi: 10.1051/0004-6361/201219774. A69.
  4. ^ a b Ginestet, N.; et al. (1999). "Spectral classifications in the near infrared of stars with composite spectra. III. Study of a sample of 137 objects with the Aurelie spectrograph". Astronomy and Astrophysics Supplement. 134 (3): 473. Bibcode: 1999A&AS..134..473G. doi: 10.1051/aas:1999444.
  5. ^ a b c d e Hartkopf, William I.; et al. (2008). "Speckle Interferometry at the Usno Flagstaff Station: Observations Obtained in 2003-2004 and 17 New Orbits". The Astronomical Journal. 135 (4): 1334. Bibcode: 2008AJ....135.1334H. doi: 10.1088/0004-6256/135/4/1334. Archived from the original on June 24, 2017.
  6. ^ a b c Holmberg, J.; et al. (2007). "The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk". Astronomy & Astrophysics. 475 (2): 519–537. arXiv: 0707.1891. Bibcode: 2007A&A...475..519H. doi: 10.1051/0004-6361:20077221. S2CID  119054949.
  7. ^ a b c d Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv: 1103.4651, Bibcode: 2011A&A...530A.138C, doi: 10.1051/0004-6361/201016276, S2CID  56118016
  8. ^ "pi.02 UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-08.
  9. ^ "The astronomical magnitude scale". International Comet Quarterly. Retrieved 2020-12-17.