ゲンマ

The brightest star of Corona Borealis, the Northern Crown, Alphecca bears the Alpha designation of that small constellation. It is a white A-type star, its colour index of 0.032 lying just off the neutral point typical of the class. Alphecca shines at apparent magnitude 2.22 and lies about 75 light-years away; its absolute magnitude of 0.41 indicates a luminosity moderately above solar levels, its modest distance keeping apparent and true brightness fairly close. Alphecca sits at the centre of the semicircular arc of stars that gives Corona Borealis its crown-like shape, the most prominent point of that compact northern pattern of the summer sky.