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Crux is the smallest of the 88 modern constellations, but also one of the most immediately recognisable. Its four brightest stars make up the Southern Cross. Crux lies in the far southern sky and is circumpolar from many southern hemisphere locations, but it appears highest in the evening sky in the months around March. It is depicted on numerous national and regional flags, including those of Australia and New Zealand.

Crux lies centrally within the plane of the Milky Way, and is also rich with deep sky objects, including the bright open cluster NGC 4755, commonly known as the Jewel Box.

The Coalsack Nebula, also known as C99, lies between the four stars of the southern cross, and is the most prominent of all dark nebulae. Its presence in Crux reflects the fact that this one of the most heavily dust-obscured parts of the galaxy.

The name ‘Crux’ was first used for this sky area in 1598 by Petrus Plancius and Jodocus Hondius. It was known to ancient astronomers, who considered it to be the hind legs of Centaurus.

Nowadays it lies too far south to be seen from European latitudes, but in the past this was not the case. The precession of the equinoxes is gradually moving this area of the sky closer to the south celestial pole. It was possible to observe Crux from Athens up until around 400 AD.