Pi2 Ursae Minoris
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 15h 39m 38.61131s |
| Declination | +79° 58′ 59.5495″ |
| Apparent magnitude (V) | 6.89 (7.32 + 8.15) |
| Characteristics | |
| Spectral type | F1V + G0 |
| B−V color index | 0.392±0.015 |
| Astrometry | |
| Radial velocity (Rv) | −32.10±1.8 km/s |
| Proper motion (μ) | RA: −32.643 mas/yr Dec.: 41.425 mas/yr |
| Parallax (π) | 8.1090±0.2844 mas |
| Distance | 400 ± 10 ly (123 ± 4 pc) |
| Absolute magnitude (MV) | 1.69±0.08 |
| Orbit | |
| 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 M☉ |
| Radius | 3.82+0.59 −1.27 R☉ |
| Luminosity | 16.5±0.7 L☉ |
| Temperature | 6,858±80 K |
| Metallicity [Fe/H] | +0.09 dex |
| Age | 1.20 Gyr |
| Other designations | |
| π2 UMi, 18 Ursae Minoris, BD+80°487, HD 141652, HIP 76695, SAO 2588, WDS J15396+7959AB | |
| 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, which can be viewed with a pair of binoculars. 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.
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, so the grade of the orbital elements is rated as poor. The system has a high eccentricity of 0.96 and they orbit each other with a period of roughly 172 years. The magnitude 7.32 primary is an F-type main-sequence star with a stellar classification of F1V. The fainter secondary has a magnitude of 8.15 and is G-type star. At present the angular separation between both stars is 0.67 arcseconds [1].