Crux

Origin

The Crux constellation, also known as the Southern Cross, is a small but prominent constellation in the southern hemisphere's night sky. It is one of the most famous and easily recognizable constellations in the southern celestial hemisphere. Crux is notable for its distinctive cross shape, and it appears as a symbol on various national flags and emblems, including those of Australia, New Zealand, and several other countries in the southern hemisphere.

The stars of Crux were known in antiquity as part of the rear legs of Centaurus, the Centaur. Their separation as Crux, The Cross, goes back to the navigator of Amerigo Vespucci, Andrea Corsali, who used the asterism in the early 1500s to triangulate the southern pole. In his letter to his donators, the Medici family of Florence, he referred to this asterism as the “four guiding stars” mentioned by their compatriot Dante Alighieri in his Divine Comedy, there metaphorically representing the ancient Roman (and Christian) cardinal virtues prudence, justices, fortitude, and temperance.”

Crux was not visible from many northern latitudes, so it was not well known to ancient civilizations in Europe and the Mediterranean region. Instead, it was primarily observed and recognized by the indigenous peoples of the southern hemisphere, including the Indigenous Australians and various South Pacific island cultures.

European explorers and navigators, including Ferdinand Magellan during his circumnavigation of Earth in the early sixteenth century, played a crucial role in introducing Crux to the western world. They encountered the constellation during their voyages to the southern hemisphere and brought its existence to the attention of European astronomers and cartographers.

The name Crux itself is derived from the Latin word for a cross, and it reflects the constellation's distinctive shape. Over time, Crux became an important navigational tool for sailors in the southern hemisphere because its position in the night sky helped them determine their latitude.

Bright Stars

The Crux constellation contains several bright stars that are easily visible in the night sky of the southern hemisphere. Some of the brightest stars in the Crux constellation include:

1. Alpha Crucis: Also known as Acrux, Alpha Crucis is the brightest star in the Crux constellation and the thirteenth-brightest star in the entire sky. It is a binary star system consisting of two blue-white stars that are relatively close together. Acrux is one of the stars that form the distinctive cross shape of the constellation.

2. Beta Crucis : Beta Crucis, also known as Mimosa, is the second-brightest star in Crux. It is another blue-white giant star and is also part of the Southern Cross asterism.

3. Gamma Crucis:: Gamma Crucis is a red giant star and is sometimes called Gacrux. It is the third-brightest star in the Crux constellation and is the star at the top of the cross.

4. Delta Crucis: Delta Crucis, also known as Imai, is a double star system consisting of a blue-white main sequence star and a fainter companion star. It is also part of the Southern Cross.

Photo of the constellation Crux produced by NOIRLab in collaboration with Eckhard Slawik, a German astrophotographer. The annotations are from a standardized set of 88 western IAU constellations and stick figures from Sky & Telescope. Please find here a non-annotated version of the image.

Credit: E. Slawik/NOIRLab/NSF/AURA/M. Zamani