What kind of star is Algieba?
Algieba, catalogued as Gamma Leonis (γ Leo; name applies to component A), appears in the official constellation Leo. Its apparent visual magnitude is about 2.0 combined, while its estimated distance is about 130 light-years. Astronomers classify the object as K-type and G-type giant visual binary; planet around component A. 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.
Gamma Leonis is a gravitationally bound visual binary containing two evolved stars, usually classified near K1 III and G7 III. Their long-period orbit can be tracked across generations, and the changing separation and position angle allow dynamical mass estimates when combined with distance. Precision radial velocities of component A revealed the giant planet Gamma Leonis Ab, whose multiyear orbit is entirely invisible in a telescope. Because evolved giants exhibit oscillations and activity, planet confirmation requires separating a persistent Keplerian signal from stellar noise. The proper name Algieba belongs to component A under IAU conventions, while observers commonly use it informally for the combined naked-eye point.
The coordinate pair RA 10h 19m 58.35s, Dec +19° 50′ 29.4″ 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.
Algieba data at a glance
| Proper name | Algieba | Catalogue designation | Gamma Leonis (γ Leo; name applies to component A) |
|---|---|---|---|
| Constellation | Leo | Apparent magnitude | about 2.0 combined |
| Spectral or system type | K-type and G-type giant visual binary; planet around component A | Estimated distance | about 130 light-years |
| Right ascension (J2000) | 10h 19m 58.35s | Declination (J2000) | +19° 50′ 29.4″ |
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 Algieba
Algieba derives from Arabic al-jabha, “the forehead.” Its position in many modern Leo drawings is closer to the mane or neck, illustrating how constellation anatomy changed as names crossed languages and chart traditions.
Algieba's name came through Arabic astronomy, while Gamma Leonis was assigned in Bayer's Uranometria. Nineteenth-century double-star observers repeatedly measured the pair and established orbital motion. The system later joined the exoplanet era when radial-velocity work found a planet around the primary. Its position in the Sickle also makes it a standard public-observing target during clear northern spring evenings each year.
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 Algieba
Algieba sits in Leo's Sickle above Regulus. A steady small telescope at roughly 75× or more splits it into a striking pair of golden-yellow stars; the separation changes slowly over their long orbit. Good seeing matters more than extreme aperture for this bright double.
Visible from most of the world and particularly well placed on northern spring evenings. 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 evening months are February through May.
- Find it on the curve of Leo's Sickle above Regulus.
- Use about 75–150× under steady seeing to split the pair.
- The exoplanet cannot be seen directly in ordinary amateur equipment.
Interesting facts about Algieba
- Algieba is a genuine visual binary, not an optical alignment.
- Both visible stars are evolved giants.
- A giant exoplanet orbits component A.
- The proper name formally applies to the A component.
- Its two warm-coloured points are a celebrated small-telescope sight.
Continue from Algieba into the night sky
Use the Leo 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.