What kind of star is Mimosa?
Mimosa, catalogued as Beta Crucis (β Cru; name applies to component Aa), appears in the official constellation Crux. Its apparent visual magnitude is about 1.23–1.31, while its estimated distance is approximately 280 light-years. Astronomers classify the object as B0.5 III primary; multiple system. 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 47m 43.27s, Dec −59° 41′ 19.6″ 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 Mimosa
The origin of Mimosa is uncertain; Becrux, a contraction of Beta Crucis, is a historical alternative. The IAU name applies specifically to β Crucis Aa.
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 Mimosa
Locate compact Crux beside the Southern Pointers. Mimosa is the bright blue-white star on the Cross’s eastern arm. Its variability is too slight for casual naked-eye detection.
Southern sky; circumpolar across much of the Southern Hemisphere and invisible from most 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 Mimosa
- Mimosa is the second-brightest star in Crux after Acrux.
- It is a multiple blue-white star system.
- The primary is a Beta Cephei variable with small, rapid pulsations.
- Its oscillations make it valuable for asteroseismology, which probes stellar interiors.
- Mimosa forms the eastern arm of the Southern Cross.
Sources and further reading
Measurements are rounded for readability. Multiple systems, variable stars and distant supergiants can have component-specific or model-dependent values.