Pi2 Ursae Minoris

For other stars with this Bayer designation, see π Ursae Minoris.
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]
Characteristics
Spectral type F1V[4] + G0[5]
B−V color index 0.392±0.015[2]
Astrometry
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)
(secondary)		274.0±22.4°
Details
Mass1.87[7] M☉
Radius3.82+0.59
−1.27[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
SIMBADdata

Pi2 Ursae Minoris, which is Latinized from π2 UMi / π2 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 Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Malkov_et_al_2012 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference ginestet_et_al_1999 was invoked but never defined (see the help page).
  5. ^ a b c d e Cite error: The named reference Hartkopf_et_al_2008 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Holmberg_et_al_2007 was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference Casagrande_et_al_2011 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference ICQ was invoked but never defined (see the help page).