Tukuk-OS✨ Crux
Cru · cross · Southern sky
Crux is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin, meaning cross; stars within it are named in the genitive form Crucis.
Facts about Crux
| Constellation | Crux |
|---|---|
| IAU abbreviation | Cru |
| Genitive (Latin) | Crucis |
| Meaning | cross |
| Brightest star | Acrux (apparent magnitude 0.76) |
| Area | 68 square degrees |
| Hemisphere | Southern |
How big is Crux on the sky?
With an area of 68 square degrees, Crux is number 88 of 88 constellations by size — 0.2% of the whole celestial sphere. That is roughly 340 full moons of sky side by side (the Moon’s disc covers about 0.2 square degrees). The ranking runs from Hydra, the largest at 1,303°, down to Crux, the smallest at 68°; Crux sits between neighbours Equuleus (72°).
It is worth remembering what those borders are: since 1922 the IAU has drawn the 88 constellations as precise regions tiling the entire sky, so every star, every galaxy and every empty patch belongs to exactly one of them — ancient figures, modern surveying.
The name in use
Stars and variable objects inside Crux are labelled with its genitive (possessive) form, Crucis: the Bayer designations run Alpha, Beta, Gamma… Crucis, and deep-sky objects are often called “of Crucis” in catalogues and papers. The Greek letters roughly follow brightness but do not always obey it — history, not rules, decided which star got Alpha. The Latin meaning of the name is cross; southern skies carry its brightest members, of which Acrux shines at apparent magnitude 0.76.
Who can see it: a southern-sky constellation: from mid-southern latitudes it rides high, and from far north of the equator it never properly rises. From the equator, in the course of a year, well-nigh every constellation in the catalogue crosses the sky — the further you travel from it, the more of the opposite hemisphere you permanently leave behind.