What kind of star is Mirfak?
Mirfak, catalogued as Alpha Persei (α Per), appears in the official constellation Perseus. Its apparent visual magnitude is about 1.79, while its estimated distance is roughly 510 light-years. Astronomers classify the object as F5 Ib yellow-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.
Mirfak is an evolved intermediate-to-high-mass supergiant associated with the Alpha Persei Cluster and moving group. Cluster membership supplies a shared age, distance and chemical context that isolated stars lack, allowing evolutionary models to be tested against less-evolved neighbours. The cluster is young on Galactic timescales, approximately tens of millions of years old, and stretches across several degrees. Mirfak’s F-type spectrum means its surface is cooler than the hot B stars common in young groups, not because it is older than the cluster but because its greater mass drove it rapidly into an expanded post-main-sequence state.
The coordinate pair RA 03h 24m 19.37s, Dec +49° 51′ 40.2″ 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.
Mirfak data at a glance
| Proper name | Mirfak | Catalogue designation | Alpha Persei (α Per) |
|---|---|---|---|
| Constellation | Perseus | Apparent magnitude | about 1.79 |
| Spectral or system type | F5 Ib yellow-white supergiant | Estimated distance | roughly 510 light-years |
| Right ascension (J2000) | 03h 24m 19.37s | Declination (J2000) | +49° 51′ 40.2″ |
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 Mirfak
Mirfak comes from Arabic mirfaq al-thurayyā, “elbow of the Pleiades,” from an Arabic sky figure different from the Greek Perseus. Algenib is a historical alternative but is now officially used for Gamma Pegasi.
The proper name originated in an Arabic figure linked to the Pleiades and was later attached to Alpha Persei in European catalogues. The alternative Algenib created ambiguity because that name also circulated for Gamma Pegasi; modern IAU usage reserves Algenib for the Pegasus star and Mirfak for Alpha Persei. The surrounding cluster entered twentieth-century catalogues as Melotte 20 and has since become an important nearby young association studied with astrometry.
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 Mirfak
Mirfak is the brightest star in Perseus and sits inside the Alpha Persei Cluster, also called Melotte 20. The star and much of the cluster fit comfortably into binoculars, producing a loose, sparkling field that is most impressive at low power rather than through a narrow telescope eyepiece.
Circumpolar from many northern locations and highest on late-autumn and winter 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 brightest star midway between Cassiopeia and the Pleiades region.
- Use 7× or 10× binoculars so the broad Alpha Persei Cluster fits in one field.
- Avoid high magnification; the cluster’s loose structure spans several degrees.
- Compare Mirfak’s pale yellow-white light with orange stars and bluer cluster members.
Interesting facts about Mirfak
- Mirfak is the brightest star in Perseus.
- It is associated with the Alpha Persei Cluster, catalogued as Melotte 20.
- Mirfak is an evolved supergiant even though its surrounding cluster is young.
- The cluster is a large binocular target rather than a compact telescopic object.
- The old alternative Algenib is now officially assigned to Gamma Pegasi.
Continue from Mirfak into the night sky
Use the Perseus 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.