What kind of star is Alkaid?
Alkaid, catalogued as Eta Ursae Majoris (η UMa), appears in the official constellation Ursa Major. Its apparent visual magnitude is about 1.85, while its estimated distance is about 104 light-years. Astronomers classify the object as B3 V main-sequence star. 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.
Alkaid is a young B-type main-sequence star that produces far more ultraviolet radiation than the Sun. Although projected beside the Dipper’s co-moving central stars, its velocity and distance exclude it from the Ursa Major Moving Group. Together with Dubhe, it will gradually distort the asterism as stellar proper motions accumulate over tens of thousands of years. The star rotates rapidly, broadening features in its spectrum, yet it is not known as the kind of emission-line Be star represented by Gamma Cassiopeiae. Its high mass gives it a much shorter main-sequence lifetime than a solar-type star.
The coordinate pair RA 13h 47m 32.44s, Dec +49° 18′ 47.8″ 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.
Alkaid data at a glance
| Proper name | Alkaid | Catalogue designation | Eta Ursae Majoris (η UMa) |
|---|---|---|---|
| Constellation | Ursa Major | Apparent magnitude | about 1.85 |
| Spectral or system type | B3 V main-sequence star | Estimated distance | about 104 light-years |
| Right ascension (J2000) | 13h 47m 32.44s | Declination (J2000) | +49° 18′ 47.8″ |
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 Alkaid
Alkaid derives from Arabic qāʾid banāt naʿsh, “leader of the daughters of the bier.” Benetnasch is a historical alternative from the same phrase.
The traditional Arabic pattern did not simply duplicate the Greek Great Bear: the handle stars were imagined as mourners following a funerary bier, with Alkaid as their leader. The alternative Benetnasch preserves another compression of the same expression. Bayer assigned Eta Ursae Majoris. When the IAU standardized common names, it chose Alkaid, a decision explicitly noted on its historical Ursa Major illustration.
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 Alkaid
Trace the Big Dipper’s handle to its outermost tip. Alkaid is the bright blue-white endpoint beyond Mizar. Following the handle’s curve in the other direction and continuing its arc leads toward Arcturus, while Alkaid itself points into the northern spring galaxy fields.
Visible across the Northern Hemisphere and circumpolar at many northern latitudes; best on 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
- Find the outermost star at the tip of the Dipper’s curved handle.
- Compare Alkaid’s blue-white light with orange Dubhe across the asterism.
- Sweep southeast from Alkaid for the galaxy-rich regions of Canes Venatici and Ursa Major.
- Do not count it as a moving-group member simply because it belongs to the Dipper pattern.
Interesting facts about Alkaid
- Alkaid is the third-brightest star in Ursa Major.
- It is the hottest of the seven principal Big Dipper stars.
- Unlike the five central Dipper stars, it is not in the Ursa Major Moving Group.
- Its historical alternative name is Benetnasch.
- Alkaid is a main-sequence star but will exhaust core hydrogen much sooner than the Sun.
Continue from Alkaid into the night sky
Use the Ursa Major 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.