Pi2 Ursae Minoris

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]

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]
Distance	400 ± 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
Mass	1.87[7] M☉
Radius	3.82+0.59 −1.27[1] R☉
Luminosity	16.5±0.7[1] L☉
Temperature	6,858±80[7] K
Metallicity [Fe/H]	+0.09[7] dex
Age	1.20[7] Gyr
Other designations
π2 UMi, 18 Ursae Minoris, BD+80°487, HD 141652, HIP 76695, SAO 2588, WDS J15396+7959AB[8]
Database references
SIMBAD	data

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 .