- ACHERNAR (Alpha Eridani). There are 22 classical “first magnitude” stars in the sky. Of these, nine are so bright that in modern times they had to be placed into even brighter categories, seven into “zeroth” magnitude (the brightest of which is Alpha Centauri) and two (Canopus and Sirius) into the exclusive “minus-first magnitude” group. Of these nine, Achernar ranks last, right behind Procyon in Canis Minor and just beating out Hadar in southern Centaurus.