Alioth
Alioth /ˈæliɒθ/, also called Epsilon Ursae Majoris, is a star in the northern constellation of Ursa Major. The designation is Latinised from ε Ursae Majoris and abbreviated Epsilon UMa or ε UMa. Despite being designated "ε" (epsilon), it is the brightest star in the constellation and at magnitude 1.77 is the thirty-third brightest star in the sky.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 12h 54m 01.74959s |
| Declination | +55° 57′ 35.3627″ |
| Apparent magnitude (V) | 1.77 |
| Characteristics | |
| Spectral type | A1III-IVp kB9 |
| U−B color index | +0.02 |
| B−V color index | −0.02 |
| Variable type | α2 CVn |
| Astrometry | |
| Radial velocity (Rv) | −9.3 km/s |
| Proper motion (μ) | RA: +111.91 mas/yr Dec.: −8.24 mas/yr |
| Parallax (π) | 39.51 ± 0.20 mas |
| Distance | 82.6 ± 0.4 ly (25.3 ± 0.1 pc) |
| Absolute magnitude (MV) | −0.2 |
| Details | |
| Mass | 2.91 M☉ |
| Radius | 4.14 R☉ |
| Luminosity | 102 L☉ |
| Surface gravity (log g) | 3.23 cgs |
| Temperature | 9,020 K |
| Metallicity [Fe/H] | +0.00 dex |
| Rotational velocity (v sin i) | 33 km/s |
| Age | 300 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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.[1]
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