Alkaid

Alkaid
Location of Alkaid (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 13h 47m 32.43776s[1]
Declination +49° 18′ 47.7602″[1]
Apparent magnitude (V) +1.86[2]
Characteristics
Spectral type B3 V[3]
U−B color index −0.68[2]
B−V color index −0.19[2]
Astrometry
Radial velocity (Rv)−10.9[4] km/s
Proper motion (μ) RA: −121.17[1] mas/yr
Dec.: −14.91[1] mas/yr
Parallax (π)31.38 ± 0.24 mas[1]
Distance103.9 ± 0.8 ly
(31.9 ± 0.2 pc)
Absolute magnitude (MV)−0.67[5]
Details
Mass6.1±0.1[6] M☉
Radius3.4±0.5[7] R☉
Luminosity594±31[7] L☉
Surface gravity (log g)3.78[7] cgs
Temperature15,540±1,157[7] K
Rotational velocity (v sin i)150[8] km/s
Age10.0±2.6[6] Myr
Other designations
Alkaid, Benetnash, Benetnasch,[9] Elkeid, η UMa, 85 UMa, BD+50°2027, FK5 509, GC 18643, HD 120315, HIP 67301, HR 5191, PPM 53742, SAO 44752.
Database references
SIMBADdata

Alkaid /ælˈkeɪd/, also called Eta Ursae Majoris (Latinised from η Ursae Majoris, abbreviated Eta UMa, η UMa),[10][11] is a star in the constellation of Ursa Major. It is the most eastern (leftmost) star in the Big Dipper (or Plough) asterism. However, unlike most stars of the Big Dipper, it is not a member of the Ursa Major moving group.[12] With an apparent visual magnitude of +1.86, it is the third-brightest star in the constellation and one of the brightest stars in the night sky.

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