Ursa Major 5

Alcor
80 Ursae Majoris


Distance (Light Years) 81.2 ± 1.2
Visual Magnitude 3.99
Color (B-V) 0.16

Description of the Star

Alcor is a hot, white A5V main sequence star having a luminosity about 13 times that of the sun.
The spectral type implies that Alcor has an effective temperature of 8500 K, a diameter 1.7 times that of the sun, and a mass of about 2.2 solar masses.

Alcor is a variable star of Delta Scuti type; see Caph.

The Ursa Major Cluster

According to Burnham, Alcor is part of a star cluster including at least 16 other stars from the Ursa Major area of the sky, as well as Alioth, Merak, Mizar, Phecda, and Megrez in the Big Dipper. The Ursa Major cluster represents an ellipsoidal volume of space about 30 ly long by 18 ly in width.

Alioth
Epsilon Ursae Majoris

Distance (Light Years) 80.9 ± 1.2
Visual Magnitude 1.76
Color (B-V) -0.02

Names For This Star

According to Allen, the first usage of the name "Alioth" for this star was in the Alfonsine Tables published in Spain in 1252 under the patronage of King Alfonso X of Leon and Castile. The only etymology offered is the name may originate with the word Alyat meaning "The Fat Tail of the Eastern Sheep". This derivation is unlikely.
A variant spelling is "Aliath."

Description of the Star

Alioth is a white star of spectral type A0pCr. The spectrum of the star is characterized by abnormally strong lines of chromium and europium (Burnham). The diameter of the star is given in the The Bright Star Catalog as 4 times that of the sun.
According to Burnham, Alioth is part of a star cluster including at least 16 other stars from the Ursa Major area of the sky, as well as Mizar, Merak, Alcor, Phecda, and Megrez in the Big Dipper. The Ursa Major cluster represents an ellipsoidal volume of space about 30 ly long by 18 ly in width.


Alkaid
Eta Ursae Majoris

Distance (Light Years) 100.7 ± 2.3
Visual Magnitude 1.85
Color (B-V) -0.19

Names For This Star

This star is also known as Benetnash, Benetnasch, or Elkeid. All the names for this star derive from the Arabic phrase Al Ka'id Banat al Na'ash, which means literally "the Governor of the Daughters of the Bier", that is, "The Chief of the Mourners." The mourners in Arabic poetry seem to have been the three stars of the handle of the Big Dipper: Alkaid, Mizar, and Alioth.
Description of the Star

Alkaid is a blue B3V main sequence star. This spectral type indicates an effective temperature of 9100 K, a diameter twice that of the sun, and a luminosity 4300 times that of the sun, and a mass perhaps 13 times that of the sun.