Eta Ursae Majoris

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**Eta Ursae Majoris**
Observation data Epoch J2000
Constellation	Ursa Major
Right ascension	13^h 47^m 32.4^s
Declination	+49° 18′ 48″
Apparent magnitude (V)	1.85
Spectral Characteristics
Spectral type	B3 V
U-B color index	-0.67
B-V color index	-0.19
Variable type	?
Astrometry
Radial velocity (R_v)	-11 km/s
Proper motion (μ)	RA: -121.23 mas/yr Dec.: -15.56 mas/yr
Parallax (π)	32.39 ± 0.74 mas
Distance	101 ± 2 ly (30.9 ± 0.7 pc)
Absolute magnitude (M_V)	-0.60
Physical Characteristics
Mass	6 M_☉
Radius	1.8 R_☉
Luminosity	700 L_☉
Temperature	22,000 K
Metallicity	?
Rotation	~200 km/s
Age	? years
Other designations
Alkaid, Benetnash, Benetnasch, Elkeid, 85 Ursae Majoris, HR 5191, BD +50°2027, HD 120315, SAO 44752, FK5 509, GC 18643, HIP 67301.

Eta Ursae Majoris (η UMa / η Ursae Majoris) is a star in the constellation Ursa Major. It also has the traditional names Alkaid (or Elkeid) and Benetnash (Benetnasch).

It is known as 北斗七 (the Seventh Star of the Northern Dipper) or 搖光 (the Star of Twinkling Brilliance) in Chinese.

Alkaid is the most eastern (leftmost) star in the Big Dipper (Plough) asterism. However, unlike most stars of the Big Dipper it is not a member of the Ursa Major moving group.

Alkaid has apparent magnitude +1.9, making it the 35th brightest star in the sky. It is a young bluish-white main sequence star of spectral class B3 V. At 20,000 kelvins it is one of the hotter stars visible with the naked eye.

The name derives from القائد البنات النعش, al-qāid al-banāt an-nac meaning "The leader of the daughters of the bier". The daughters of the bier, i.e. the mourning maidens, are the three stars of the handle of the Big Dipper, Alkaid, Mizar, and Alioth.