A

David

Darling

Alioth (Epsilon Ursae Majoris)

Alioth

Alioth (Epsilon Ursae Majoris) is the brightest star in the constellation Ursa Major and the third star from the end of the Big Dipper's handle; its proper name comes from a corruption of the Arabic for "black horse."

 

Alioth is the brightest Ap star and is also an Alpha2 Canum Venaticorum star with a period of 5.1 days. Its oxygen abundance is 100,000 times greater near the magnetic equator than near the magnetic poles (which are displaced from the rotational equator and poles); the amount of chromium varies similarly. Though visually the brightest Ap star, Alioth has one of the weakest magnetic fields of this class – 15 times weaker than that observed for Cor Caroli.

 

visual magnitude 1.76
absolute magnitude -0.22
spectral type A0V
surface temperature 9,400 K
luminosity 108 Lsun
mass about 3 Msun
distance 81 light-years (25 pc)
position RA 12h 54m 01.7s,
Dec +55° 57' 35"
other designations Aliath, 77 Ursae Majoris,
HR 4905, BD +56°1627,
HD 112185, GCTP 2964.00,
SAO 28553, FK5 483,
CCDM 12540+5558, HIP 62956