Epsilon Ursae Majoris
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| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 12h 54m 01.74959s[1] |
| Declination | +55° 57′ 35.3627″[1] |
| Apparent magnitude (V) | 1.77[2] |
| Characteristics | |
| Spectral type | A1III-IVp kB9 |
| U−B color index | +0.02[2] |
| B−V color index | -0.02[2] |
| Variable type | α2 CVn |
| Astrometry | |
| Radial velocity (Rv) | -9.3[3] km/s |
| Proper motion (μ) | RA: +111.91[1] mas/yr Dec.: -8.24[1] mas/yr |
| Parallax (π) | 39.51 ± 0.20[1] mas |
| Distance | 82.6 ± 0.4 ly (25.3 ± 0.1 pc) |
| Absolute magnitude (MV) | –0.2[4] |
| Details | |
| Mass | 2.91[5] M☉ |
| Radius | 4.14[6] R☉ |
| Luminosity | 102[7] L☉ |
| Surface gravity (log g) | 3.23[8] cgs |
| Temperature | 9,020[8] K |
| Metallicity [Fe/H] | +0.00[4] dex |
| Rotational velocity (v sin i) | 33[9] km/s |
| Age | 300[10] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Epsilon Ursae Majoris (Latinised from ε Ursae Majoris, abbreviated Epsilon UMa, ε UMa), officially named Alioth /ˈæliɒθ/,[11][12] is, despite being designated "ε" (epsilon), the brightest star in the constellation of Ursa Major, and at magnitude 1.77 is the thirty-second brightest star in the sky.
It is the star in the tail of the bear closest to its body, and thus the star in the handle of the Big Dipper (or Plough) closest to the bowl. It is also a member of the large and diffuse Ursa Major moving group. Historically, the star was frequently used in celestial navigation in the maritime trade, because it is listed as one of the 57 navigational stars.
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