11 Ursae Minoris, formally named Pherkad Minor, is a single[8] star located approximately 410 light-years away[1] in the northern circumpolar constellation of Ursa Minor. The star is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.15.[2] It is moving closer to the Earth with a heliocentric radial velocity of −17.8 km/s.[1]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 15h 17m 05.88946s[1] |
| Declination | +71° 49′ 26.0473″[1] |
| Apparent magnitude (V) | 5.15[2] |
| Characteristics | |
| Spectral type | K4 III[3] |
| Apparent magnitude (B) | 6.664[2] |
| Apparent magnitude (J) | 2.657[2] |
| Apparent magnitude (H) | 1.931±0.192[2] |
| Apparent magnitude (K) | 1.701±0.198[2] |
| B−V color index | 1.514±0.004[2] |
| Astrometry | |
| Radial velocity (Rv) | −17.80±0.12[1] km/s |
| Proper motion (μ) | RA: +4.073 mas/yr[1] Dec.: +9.477 mas/yr[1] |
| Parallax (π) | 7.9260±0.1249 mas[1] |
| Distance | 412 ± 6 ly (126 ± 2 pc) |
| Absolute magnitude (MV) | −0.37[4] |
| Details | |
| Mass | 2.60+0.48 −0.44[5] M☉ |
| Radius | 29.14±0.45[5] R☉ |
| Luminosity | 250±6[6] L☉ |
| Habitable zone inner limit | 15.63±0.57[5] AU |
| Habitable zone outer limit | 30.65±1.10[5] AU |
| Surface gravity (log g) | 1.78±0.04[6] cgs |
| Temperature | 4,253±25[6] K |
| Metallicity | −0.02±0.05[6] |
| Age | 639+507 −278[5] Myr |
| Other designations | |
| Pherkad Minor, 11 UMi, BD+72°678, HD 136726, HIP 74793, HR 5714, SAO 8207, PPM 8870, GCRV 8864[7] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Nomenclature
edit11 Ursae Minoris is the star's Flamsteed designation. It is sometimes named Pherkad Minor (alternatively spelled Pherkard), in reference to the brighter nearby star Pherkad (Major) which is γ Ursae Minoris.[9] The name originated with Giuseppe Piazzi.[10] It has also been designated as γ1 Ursae Minoris, in which case the brighter Pherkad is called γ2 Ursae Minoris, but these names are rarely used.[9] The IAU Working Group on Star Names approved the name Pherkad Minor for 11 Ursae Minoris on 22 March 2026 and it is now so entered in the IAU Catalog of Star Names.[10]
Stellar properties
editThis is an aging K-type giant star with a stellar classification of K4 III.[3] It is 600 million years old with twice the mass of the Sun. As a consequence of exhausting the hydrogen at its core, the star has expanded to 29 times the Sun's radius.[5] It is radiating 250 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,253 K.[6]
Planetary system
edit11 Ursae Minoris has a detected planet discovered in August 2009.[4] 11 Ursae Minoris b was discovered during a radial velocity survey of 62 K type red giant stars using the 2m Alfred Jensch telescope of the Thuringian State Observatory in Germany.[4]
A newer mass measurement of the host star implies a larger planetary mass of 14.15±1.23 MJ, which would likely make 11 Ursae Minoris b a low-mass brown dwarf.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination (°) |
Radius |
|---|---|---|---|---|---|---|
| b | ≥14.15±1.23 MJ | 1.54 ± 0.07 | 516.22 ± 3.25 | 0.08 ± 0.03 | — | — |
References
edit- 1 2 3 4 5 6 7 8 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- 1 2 3 4 5 6 7 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.
- 1 2 Baines, Ellyn K.; et al. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 155 (1). 30. arXiv:1712.08109. Bibcode:2018AJ....155...30B. doi:10.3847/1538-3881/aa9d8b. S2CID 119427037.
- 1 2 3 4 Döllinger, P.; et al. (2009). "Planetary companions around the K giant stars 11 Ursae Minoris and HD 32518". Astronomy and Astrophysics. 505 (3): 1311–1317. arXiv:0908.1753. Bibcode:2009A&A...505.1311D. doi:10.1051/0004-6361/200911702. S2CID 9686080.
- 1 2 3 4 5 6 7 Baines, Ellyn K.; Jones, Jeremy; Clark, James H.; Schmitt, Henrique R.; Stone, Jordan M. (January 2025). "Eighteen Exoplanet Host Stars from the NPOI Data Archive". The Astronomical Journal. 169 (2): 83. arXiv:2506.02934. doi:10.3847/1538-3881/ad9bb1. ISSN 1538-3881.
- 1 2 3 4 5 Soubiran, C.; Creevey, O.; Lagarde, N.; Brouillet, N.; Jofré, P.; Casamiquela, L.; Heiter, U.; Aguilera–Gómez, C.; Vitali, S.; Worley, C.; de Brito Silva, D. (February 2024). "Gaia FGK benchmark stars: Fundamental Teff and log ɡ of the third version (Corrigendum)". Astronomy & Astrophysics. 693: C3. arXiv:2310.11302. doi:10.1051/0004-6361/202453050e. ISSN 0004-6361.
- ↑ "11 UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 September 2012.
- ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
- 1 2 Kostjuk, N. D. (2004). "VizieR Online Data Catalog: HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)". VizieR On-line Data Catalog: IV/27A. Originally Published in: Institute of Astronomy of Russian Academy of Sciences (2002). 4027. Bibcode:2004yCat.4027....0K.
- 1 2 "IAU Catalog of Star Names". Retrieved 23 March 2026.
External links
edit- Jean Schneider (2011). "Notes for star 11 UMi". Extrasolar Planets Encyclopaedia. Archived from the original on August 19, 2009. Retrieved 30 September 2011.