What kind of star is Zosma?
Zosma, catalogued as Delta Leonis (δ Leo), appears in the official constellation Leo. Its apparent visual magnitude is about 2.56, while its estimated distance is about 58 light-years. Astronomers classify the object as A4 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.
Delta Leonis is an A-type main-sequence star, hotter, more massive and more luminous than the Sun. Spectral-line broadening shows that it rotates rapidly, a common property of A stars that affects surface temperature distribution and complicates precise atmospheric modelling. Zosma is close enough for a well-measured parallax and has sometimes been associated kinematically with the Ursa Major moving group, although membership assessments should rely on modern velocity and age analyses rather than a simple sky position. It has not yet expanded into a giant: its luminosity class V distinguishes it from the evolved stars Algieba and Regulus's subgiant-like primary elsewhere in Leo.
The coordinate pair RA 11h 14m 06.50s, Dec +20° 31′ 25.4″ 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.
Zosma data at a glance
| Proper name | Zosma | Catalogue designation | Delta Leonis (δ Leo) |
|---|---|---|---|
| Constellation | Leo | Apparent magnitude | about 2.56 |
| Spectral or system type | A4 V main-sequence star | Estimated distance | about 58 light-years |
| Right ascension (J2000) | 11h 14m 06.50s | Declination (J2000) | +20° 31′ 25.4″ |
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 Zosma
Zosma comes from Greek zōsma, “girdle” or “loincloth.” The name reflects the star's location around the Lion's hip or rump rather than a separate mythic character.
The Greek anatomical name entered the classical and later Latin catalogue traditions, while Bayer labelled the star Delta Leonis. In common Western line drawings it marks the Lion's haunch, helping form a rear-body triangle with Denebola and Chertan. The IAU standard spelling “Zosma” gives a single modern form to a name that appeared with variants in many older references and atlases.
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 Zosma
Trace Leo east from the Sickle toward Denebola. Zosma is the brighter northern point where the Lion's body turns toward the tail. It is straightforward in suburban skies, and binoculars fit much of Leo's rear triangle into a useful orientation view.
Visible from most inhabited latitudes and best in the evening during northern spring. 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 March through June.
- Follow Leo eastward from the Sickle toward Denebola.
- Use binoculars for the rear-body triangle rather than high magnification.
- Its white colour is clearest beside a cooler comparison star.
Interesting facts about Zosma
- Zosma is only about 58 light-years away.
- It is still a main-sequence star.
- Zosma's projected spin speed leaves conspicuously broadened lines in its spectrum.
- Its name describes the Lion's girdle or hip.
- It helps define Leo's hindquarter triangle.
Continue from Zosma 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.