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]
| 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 |
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].
References
edit- ^ a b c d e f g Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ a b c Malkov, O. Yu.; et al. (2012). "Dynamical Masses of a Selected Sample of Orbital Binaries". Astronomy & Astrophysics. 546: 5. Bibcode:2012A&A...546A..69M. doi:10.1051/0004-6361/201219774. A69.
- ^ a b Ginestet, N.; et al. (1999). "Spectral classifications in the near infrared of stars with composite spectra. III. Study of a sample of 137 objects with the Aurelie spectrograph". Astronomy and Astrophysics Supplement. 134 (3): 473. Bibcode:1999A&AS..134..473G. doi:10.1051/aas:1999444.
- ^ a b c d e Hartkopf, William I.; et al. (2008). "Speckle Interferometry at the Usno Flagstaff Station: Observations Obtained in 2003-2004 and 17 New Orbits". The Astronomical Journal. 135 (4): 1334. Bibcode:2008AJ....135.1334H. doi:10.1088/0004-6256/135/4/1334.
- ^ a b c Holmberg, J.; et al. (2007). "The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk". Astronomy & Astrophysics. 475 (2): 519–537. arXiv:0707.1891. Bibcode:2007A&A...475..519H. doi:10.1051/0004-6361:20077221. S2CID 119054949.
- ^ a b c d Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016
- ^ "pi.02 UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-08.
- ^ "The astronomical magnitude scale". International Comet Quarterly. Retrieved 2020-12-17.