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 | |
Database references | |
SIMBAD | data |
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].