Crux

Crux [Lat.,=cross], small but brilliant southern constellation whose four most prominent members form a Latin cross, the famous Southern Cross. The long arm of the cross, terminating in the brightest member, Acrux (Alpha Crucis), points almost directly at the south celestial pole. Two other stars, Mimosa (Beta Crucis) and Gacrux (Gamma Crucis) are also among the brightest in the sky. Also in Crux is the Coalsack, a famous dark nebula. Crux reaches its highest point in the evening sky in May; its location in the far southern sky makes it visible most of the year to southern observers but not at all to observers north of about 25°N lat.

crux pl. cruxes, cruces †conundrum, riddle XVIII; difficulty the solution of which perplexes XIX. — L., ‘CROSS 1’; short for crux interpretum, crux philosophorum torment of interpreters, of philosophers.

crux a cross (from Latin); the term is recorded from the mid 17th century, chiefly in crux ansata (‘cross with a handle’), a word for ankh. From the early 18th century, the figurative use of the decisive or most important point at issue is recorded.