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Alioth

Epsilon Ursae Majoris, 77 Ursae Majoris

White Star in Ursa Major

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Proper Name	Alioth
Bayer Designation	Epsilon Ursae Majoris
Flamsteed Number	77 Ursae Majoris
HR (BSC)	4905
HD	112185
Constellation	Ursa Major
Right Ascension	12h 54m 2s
Declination	+55° 57' 35"
Distance	83 light years 25 parsecs
Magnitude	Apparent: +1.8 Absolute: -0.3
Spectral Class	A0VpSiSr white main sequence star
Optimum Visibility	April (Usually visible from northern latitudes)
Notes	Alioth is one of the seven stars that make up the Plough or Big Dipper formation. It lies in the middle of the handle, and is marginally brighter than Dubhe or Alpha Ursae Majoris, in the Plough's share, which makes it - by a small margin - the brightest of all the stars in Ursa Major.

The star seen here in the northeastern (upper left) corner of this image is 78 Ursae Majoris, a much less luminous star that is a close neighbour to Alioth in space. Based on the most recent parallax data, the two stars may lie within two light years of one another, and indeed may be closer together than a single light year. Imagery provided by Aladin sky atlas

Despite its 'epsilon' designation, Alioth is the brightest star in Ursa Major, with a magnitude of +1.8. This white star exhibits variability of the type demonstrated by Cor Caroli (or specifically by its Alpha² Canum Venaticorum component): that is, Alioth's apparent brightness changes due to markings on its surface as the star rotates.

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