At magnitude +1.85, Eta Ursae Majoris is the third-brightest star in Ursa Major, and the 35th brightest star in the sky. It is the easternmost (end) star in the Big Dipper's handle, and has the traditional names Alkaid and Benetnash. Alkaid's Arabic name means "the leader," and refers to the three "daughters" (the handle stars of the Dipper) that stand by a funeral bier made of the Dipper's bowl. The name Benetnasch also refers to the daughters.
In Chinese, Alioth is known as the Seventh Star of the Northern Dipper, or the Star of Twinkling Brilliance.
Properties
Alkaid is almost exactly 100 light years away. It is a young bluish-white main sequence star of spectral class B3 V, with a surface temperature of about 20000 K. Like the Sun, Alkaid is a main-sequence star that shines by fusing hydrogen into helium in its core. However, its mass - six times the Sun's - renders it both hotter and over 700 times more luminous. The star is a weak source of X-rays, just below the temperature limit at which stars produce strong X-rays as a result of shock waves in their stellar winds.
Unlike the five middle stars stars of the Big Dipper, Alkaid is not a member of the Ursa Major moving group. These stars are all moving through space together as part of a loosely bound cluster. Alkaid and Dubhe, however, are moving in different directions, ultimately dooming the Dipper's shape.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]