Global InformationPi2 Ursae Minoris information
| 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 |
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].
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