Crux constellation
Crux (the Southern Cross) is a constellation in the southern sky, best seen in the evening in May. Its brightest star is Acrux (magnitude 0.76). It contains the Southern Cross. Crux covers 68 square degrees and is the 88th-largest of the 88 constellations.
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How to find the Southern Cross, step by step
Follow the Pointers (Southern Hemisphere).
- From the Southern Hemisphere (or the tropics) look south; the cross is highest on autumn evenings in April and May.
- Find the two very bright stars Alpha and Beta Centauri (Rigil Kentaurus and Hadar), the Pointers.
- Follow the line from Rigil Kentaurus through Hadar: it leads to the Southern Cross, four bright stars in a kite shape with Acrux at the foot.
- The long axis from Gacrux through Acrux points toward the south celestial pole.
Southern Cross or False Cross?
The False Cross, made of stars of Carina and Vela, is larger, fainter and has no bright Pointers next to it. The real Southern Cross is compact, has a fifth faint star off center, and the two Pointers in Centaurus point at it.
Detailed star map of Crux
Facts
| Latin name | Crux (genitive: Crucis) |
|---|---|
| Abbreviation | Cru |
| Meaning | the Southern Cross |
| Area | 68 square degrees (88th of 88) |
| Location | right ascension 12.4 h, declination −60° |
| Visible from | latitudes 25° N to 90° S (whole constellation) |
| Best month | May (at about 9 pm) |
| Brightest star | Acrux |
| Stars brighter than magnitude 6 | 35 |
| Named stars (IAU) | 5 |
| Messier objects | none |
| Neighbors | Centaurus, Musca |
How to find Crux
From 40° N (the USA, southern Europe, Japan) Crux never rises completely above the horizon. From 35° S (Australia, South Africa, Argentina) it never sets and stands highest in the south, about 65° up. The months before and after (April and June) are also good: then it is up a couple of hours earlier or later.
Crux borders Centaurus and Musca.
Stars of Crux
Crux has 35 stars brighter than magnitude 6, the limit of the naked eye under a dark sky. These are the brightest:
| Star | Designation | Magnitude | Type | Distance |
|---|---|---|---|---|
| Acrux | α1 Crucis | 0.76 | B0.5IV | 320 ly |
| Mimosa | β Crucis | 1.25 | B0.5III | 277 ly |
| Gacrux | γ Crucis | 1.63 | M3.5III | 88 ly |
| — | α2 Crucis | 1.73 | B1V | — |
| Imai | δ Crucis | 2.8 | B2IV | 455 ly |
| Ginan | ε Crucis | 3.59 | K3-4III | 230 ly |
| — | μ1 Crucis | 4.03 | B2IV-V | — |
| — | ζ Crucis | 4.04 | B2.5V | — |
| — | η Crucis | 4.15 | F2III | — |
| — | θ1 Crucis | 4.33 | Am | — |
Printable Crux map and outline
A black and white version for printing and a plain outline of the Crux figure, useful for school projects, worksheets and learning to recognize the shape.
History
Crux is introduced by the Dutch cartographer Petrus Plancius around 1600. Its official boundary was drawn by Eugène Delporte for the International Astronomical Union in 1930.
Questions about Crux
What is the brightest star in Crux?
Acrux, at magnitude 0.76, about 320 light-years away.
When can you see Crux?
Crux is best seen in the evening in May. The whole constellation is visible from latitudes between 25° N and 90° S.
How many stars are in Crux?
35 stars in Crux are brighter than magnitude 6 and can be seen with the naked eye under a dark sky; 5 of them have official IAU names.
What does Crux mean?
Crux means “the Southern Cross” in Latin. Its abbreviation is Cru and the genitive, used in star names such as α1 Crucis, is Crucis.
