| |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 16h17m 30.27025s[1] |
| Declination | +75° 45′ 19.2351″[1] |
| Apparent magnitude (V) | +4.95[2] |
| Characteristics | |
| Evolutionary stage | main sequence[3] |
| Spectral type | F5 V[4] |
| U−B color index | +0.02[2] |
| B−V color index | +0.35[2] |
| Astrometry | |
| Radial velocity (Rv) | −11.0±0.9[5] km/s |
| Proper motion (μ) | RA: −77.647[1] mas/yr Dec.: +245.726[1] mas/yr |
| Parallax (π) | 33.4190 ± 0.1103 mas[1] |
| Distance | 97.6 ± 0.3 ly (29.92 ± 0.10 pc) |
| Absolute magnitude (MV) | +2.61[6] |
| Details | |
| Mass | 1.35[7] M☉ |
| Radius | 2.0[1] R☉ |
| Luminosity | 7.7[1] L☉ |
| Surface gravity (log g) | 4.15±0.14[7] cgs |
| Temperature | 6,858±233[7] K |
| Metallicity [Fe/H] | −0.02[8] dex |
| Rotational velocity (v sin i) | 84.8[3] km/s |
| Age | 1.061[7] Gyr |
| Other designations | |
η UMi, 21 Ursae Minoris, BD+76°596, FK5 612, GC 21999, HD 148048, HIP 79822, HR 6116, SAO 8470, CCDM 16176+7545[9] | |
| Database references | |
| SIMBAD | data |
Eta Ursae Minoris (Latinized from η Ursae Minoris) is a yellow-white hued star in the northern circumpolar constellationofUrsa Minor.
This is an F-type main-sequence starofstellar classification F5 V with an apparent magnitude of +4.95, making it faintly visible to the naked eye.[10] Based upon an annual parallax shift of 33.4 mas as seen from the Earth, it is located 98 light years from the Sun. The star is moving closer to the Sun with a radial velocity of −11 km/s,[5] and is traversing the sky with a relatively high proper motion of 0.271 arc seconds per year.[11]
Eta Ursae Minoris is about one billion years old and has an estimated 1.35 times the mass of the Sun.[7] It has a high rate of spin with a projected rotational velocity of 84.8 km/s.[3] These coordinates mark a source of X-ray emission with a luminosity of 11.5×1028 erg s−1.[6] Eta Ursae Minoris may form a wide binary system with a magnitude 15.3 companion star, located at an angular separation of 228.5 arc seconds.[4]
In some Arabic star charts it is labeled انور الفرقدين ʼanwar al-farqadayn, "the brighter of the two calves", and paired with ζ Ursae Minoris as اخفي الفرقدين akhfā al-farkadain "the dimmer of the two calves". The names may originally refer to a pair of Ibexes, and are more properly applied to β UMi and γ UMi respectively, the brighter two stars in the rectangle of Ursa Minor.[12]
