Eta Ursae Minoris

Eta Ursae Minoris
Location of η Ursae Minoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ursa Minor
Right ascension 16h 17m 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]
Distance97.6 ± 0.3 ly
(29.92 ± 0.10 pc)
Absolute magnitude (MV)+2.61[6]
Details
Mass1.35[7] M☉
Radius2.0[1] R☉
Luminosity7.7[1] L☉
Surface gravity (log g)4.15±0.14[7] cgs
Temperature6,858±233[7] K
Metallicity [Fe/H]−0.02[8] dex
Rotational velocity (v sin i)84.8[3] km/s
Age1.061[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
SIMBADdata

Eta Ursae Minoris (Latinized from η Ursae Minoris) is a yellow-white hued star in the northern circumpolar constellation of Ursa Minor.

This is an F-type main-sequence star of stellar 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]

  1. ^ a b c d e f g Cite error: The named reference dr3 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference eggen1986 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Schroeder2009 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference aaa361_614 was invoked but never defined (see the help page).
  7. ^ a b c d e Cite error: The named reference David2015 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Casagrande2011 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference kalereta was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Lepine2005 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference allen was invoked but never defined (see the help page).