What kind of star is Gacrux?
Gacrux, catalogued as Gamma Crucis (γ Cru), appears in the official constellation Crux. Its apparent visual magnitude is 1.63, while its estimated distance is about 89 light-years. Astronomers classify the object as M3.5 III. These labels describe temperature, luminosity class or system components; they should not be read as a claim that every naked-eye point is a single isolated star.
The coordinate pair RA 12h 31m 09.96s, Dec −57° 06′ 47.6″ fixes the object’s direction on the celestial sphere for the J2000 reference epoch. Right ascension works like celestial longitude measured in hours, while declination works like latitude north or south of the celestial equator. Proper motion and improved measurements can refine catalogue positions, but these coordinates are sufficiently precise for a finder chart or planetarium search.
The name Gacrux
A modern contraction of “Gamma Crucis,” rather than an ancient mythological name.
Modern professional catalogues retain identifiers such as the Bayer designation alongside a proper name. The International Astronomical Union standardizes which name belongs to which component—an important distinction for systems whose combined light looks like one star from Earth.
How to find Gacrux
Gacrux is the reddish star at the northern end of the Southern Cross. Defocus binoculars slightly to emphasize its colour, then compare it with blue-white Acrux at the opposite end.
A southern star, circumpolar from many southern locations and invisible from much of Europe. Visibility on a particular night still depends on latitude, season, time, horizon obstructions, weather and local light pollution. Use the interactive atlas below to check the surrounding field before observing.
Interesting facts about Gacrux
- Gacrux is the nearest known M-type red giant to the Sun.
- Its orange-red colour contrasts with the hotter stars forming most of the Southern Cross.
- It is mildly variable rather than perfectly constant.
- A nearby-looking optical companion is not gravitationally associated with the giant.
- Crux and the Centaurus Pointers provide a practical route toward the south celestial pole.
Sources and further reading
Measurements are rounded for readability. Multiple systems, variable stars and distant supergiants can have component-specific or model-dependent values.