What kind of star is Acrab?
Acrab, catalogued as Beta¹ Scorpii (β¹ Sco; name applies to component Aa), appears in the official constellation Scorpius. Its apparent visual magnitude is 2.62 for β¹; about 2.5 for the naked-eye blend, while its estimated distance is about 400 light-years; system estimates vary. Astronomers classify the object as B1 V 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.
Beta Scorpii is a multiple system assembled from two readily catalogued visual groups, β¹ and β², each of which contains closer components. The bright β¹ primary is an early-B star; its tight companions require spectroscopy or interferometric resolution, while the wider β¹–β² pairing is accessible to small telescopes under steady skies. SIMBAD lists parallaxes near eight milliarcseconds for the principal groups, but system distance estimates remain sensitive to orbital and astrometric treatment, so about 400 light-years is a sensible rounded value. These are massive, hot, comparatively young stars associated with the Scorpius–Centaurus region. The combined unaided-eye magnitude is brighter than β¹ alone, which explains why catalogue values can look inconsistent when component labels are omitted.
The coordinate pair RA 16h 05m 26.23s, Dec −19° 48′ 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.
Acrab data at a glance
| Proper name | Acrab | Catalogue designation | Beta¹ Scorpii (β¹ Sco; name applies to component Aa) |
|---|---|---|---|
| Constellation | Scorpius | Apparent magnitude | 2.62 for β¹; about 2.5 for the naked-eye blend |
| Spectral or system type | B1 V multiple system | Estimated distance | about 400 light-years; system estimates vary |
| Right ascension (J2000) | 16h 05m 26.23s | Declination (J2000) | −19° 48′ 19.6″ |
Values are rounded for an observer-friendly overview. Consult the linked SIMBAD record for component-level identifiers, bibliography, measurement provenance and newer catalogue values.
The name Acrab
From Arabic al-ʿaqrab, “the scorpion.” Graffias is a long-used alternative associated with claws, but Acrab is the IAU-standardized name of β¹ Scorpii Aa.
Acrab preserves the Arabic word for the constellation itself, whereas the alternative Graffias came through Greek and Latin traditions connected with the claws. Modern boundaries place the star in the Scorpion's head. The IAU's component-level naming is important here because the telescope reveals several stars where historical observers saw one. Double-star catalogues retain separate component identifiers, preventing the old naked-eye name from obscuring the system's measured hierarchy.
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 Acrab
Look just northwest of Antares in the Scorpion's three-star head. At moderate magnification, split the unequal β¹ and β² points, separated by roughly fourteen arcseconds. Good focus and steady air matter more than extreme magnification.
Best during northern summer and southern winter; visible from nearly all populated latitudes. 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.
Observation checklist
- Best observed from May to August.
- Try 60–100× to separate the principal visual pair.
- Observe near culmination to limit atmospheric blur.
- Remember that the IAU name identifies Aa, while the eyepiece includes multiple components.
Interesting facts about Acrab
- Acrab is a hierarchical multiple system.
- Small telescopes can split its main visual pair.
- Its components are hot early-B stars.
- The naked-eye magnitude blends light from more than one component.
- The proper name Acrab is assigned specifically to β¹ Scorpii Aa.
Continue from Acrab into the night sky
Use the Scorpius constellation guide to place this star within its larger pattern. When you are ready to observe, compare dark-sky places, find a nearby observatory, or follow our practical guide to finding a star in the night sky. Symbolically registered names are kept separately in the searchable Star-Register catalogue.
Sources and further reading
Measurements are rounded for readability. Multiple systems, variable stars and distant supergiants can have component-specific or model-dependent values. Survey panels show photographic sky fields, not the physical surface of the star.