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Proper NameNone
Bayer DesignationNone
Flamsteed Number21 Persei
HR (BSC)873
Variable DesignationLT Persei
Right Ascension2h 57m 17s
Declination+31° 56' 3"
Distance349 light years
107 parsecs
MagnitudeApparent: +5.09
Absolute: +0.13
Spectral ClassA2VspSiEu white main sequence star (some sources prefer a B-type blue classification)
Optimum VisibilityNovember

A hot blue-white star near the southern borders of the constellation Perseus, at a distance of 349 light years from Earth. It is notable as a variable star of the Alpha2 Canum Venaticorum type, growing fainter and brighter by about a tenth of a magnitude over a period of just less than three days. 21 Persei is strong in metals, which appear to unevenly distributed over its surface, causing the oscillation in its brightness. This star is also known by the variable designation LT Persei.

Imagery provided by Aladin sky atlas