What kind of star is Alioth?
Alioth, catalogued as Epsilon Ursae Majoris (ε UMa), appears in the official constellation Ursa Major. Its apparent visual magnitude is 1.76, while its estimated distance is about 83 light-years. Astronomers classify the object as A1 III–IVp; magnetic chemically peculiar. 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.
The coordinate pair RA 12h 54m 01.75s, Dec +55° 57′ 35.4″ 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.
The name Alioth
From an Arabic name commonly connected with alyat, the broad or fatty part of a sheep’s tail, reflecting an older sky figure.
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 Alioth
Alioth is the first handle star moving away from the Big Dipper’s bowl, directly beside Megrez. It is easy to see without optical aid throughout the year at many northern latitudes.
Strongly northern and circumpolar across much of northern Europe and North America. 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.
Interesting facts about Alioth
- Alioth is the brightest star in Ursa Major despite its Epsilon designation.
- It is a magnetic chemically peculiar star whose spectrum and brightness change slightly as it rotates.
- Alioth belongs to the Ursa Major Moving Group of stars sharing motion and origin.
- Five central Big Dipper stars share this relationship, while end stars Dubhe and Alkaid do not.
- Alioth is one of the stars historically selected for celestial navigation.
Sources and further reading
Measurements are rounded for readability. Multiple systems, variable stars and distant supergiants can have component-specific or model-dependent values.