What kind of star is Aludra?
Aludra, catalogued as Eta Canis Majoris (η CMa), appears in the official constellation Canis Major. Its apparent visual magnitude is about 2.4; slightly variable, while its estimated distance is roughly 2,000 light-years; uncertain. Astronomers classify the object as B5 Ia blue-white supergiant. 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.
Eta Canis Majoris is an evolved massive star with the luminosity class Ia reserved for highly luminous supergiants. Its wind removes material from the extended atmosphere, while small brightness changes reflect instability common among such evolved high-mass stars. Distance estimates are less secure than for nearby stars because its parallax is very small; therefore radius and luminosity values in secondary references should be treated as model-dependent rather than exact. Aludra's comparatively cool B5 classification places it later than the hotter B stars Mirzam and Adhara, although all three look blue-white. The star will have a much shorter total lifetime than the Sun and is a plausible future core-collapse supernova progenitor on astronomical timescales.
The coordinate pair RA 07h 24m 05.70s, Dec −29° 18′ 11.2″ 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.
Aludra data at a glance
| Proper name | Aludra | Catalogue designation | Eta Canis Majoris (η CMa) |
|---|---|---|---|
| Constellation | Canis Major | Apparent magnitude | about 2.4; slightly variable |
| Spectral or system type | B5 Ia blue-white supergiant | Estimated distance | roughly 2,000 light-years; uncertain |
| Right ascension (J2000) | 07h 24m 05.70s | Declination (J2000) | −29° 18′ 11.2″ |
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 Aludra
Aludra comes from Arabic al-ʿudhrā, “the maiden.” The name once belonged to a small group of stars called the Maidens; modern standardization assigns Aludra specifically to Eta Canis Majoris.
Aludra's Arabic group name predates modern boundaries and did not originally describe the same isolated object presented in today's catalogues. Bayer labelled the star Eta Canis Majoris in the early seventeenth century. In current maps it commonly marks the Great Dog's tail, while the IAU's standardization preserves one historical spelling without implying that other spellings or cultural figures were mistaken.
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 Aludra
Trace Canis Major southeast from Sirius through Wezen. Aludra is the bright point at the Dog's tail in common line drawings. It is easy in binoculars and often visible without them, though extinction close to the horizon can make it less conspicuous from high northern latitudes.
Best from the Southern Hemisphere, but visible on winter evenings from much of the Northern Hemisphere with an open southern horizon. 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 January through March.
- Look southeast of Wezen at the end of the Dog's tail.
- Southern observers see it much higher above atmospheric haze.
- A small telescope does not reveal a surface; use binoculars for field context.
Interesting facts about Aludra
- Aludra is among the most distant naked-eye stars in Canis Major.
- It is intrinsically far brighter than nearby Sirius.
- Its atmosphere drives a substantial stellar wind.
- The name once referred to a group known as the Maidens.
- Its placement demonstrates the depth hidden inside constellation figures.
Continue from Aludra into the night sky
Use the Canis 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.