Alphekka (Alpha Coronae Borealis)

Alphekka and Corona Borealis

Corona Borealis and environs. Map © 2003 Torsten Bronger.

Alphekka (Alpha Coronae Borealis), also known as Gemma, is the brightest star in the constellation Corona Borealis. Its Arabic name (alternatively spelled "Alphecca"), meaning "break," refers to the broken circlet of stars that makes up the Northern Crown.


Alphekka is an Algol star: the bright naked-eye star has a much fainter, Sun-like (G5) companion, that produces a barely discernible eclipse of the primary every 17.4 days. Alphekka is also a part of the Ursa Major Moving Cluster.


visual magnitude 2.22
absolute magnitude 0.42
spectral type A0V + G5V
surface temperature 9,500 K
luminosity 60 Lsun
distance 75 light-years (23 pc)
position RA 15h 34m 41.3s,
Dec +26° 42' 53"
other designations Alphecca, Gnosia, Ashtaroth,
5 CrB, HR 5793, BD +27°2512,
HD 139006, GCTP 3519.00,
SAO 83893, FK5 578, HIP 76267