Alkaid
Alkaid /ælˈkeɪd/, also called Eta Ursae Majoris (Latinised from η Ursae Majoris, abbreviated Eta UMa, η UMa), is a star in the constellation of Ursa Major. It is the most eastern (leftmost) star in the Big Dipper (or Plough) asterism. However, unlike most stars of the Big Dipper, it is not a member of the Ursa Major moving group. With an apparent visual magnitude of +1.86, it is the third-brightest star in the constellation and one of the brightest stars in the night sky.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 13h 47m 32.43776s |
| Declination | +49° 18′ 47.7602″ |
| Apparent magnitude (V) | +1.86 |
| Characteristics | |
| Spectral type | B3 V |
| U−B color index | −0.68 |
| B−V color index | −0.19 |
| Astrometry | |
| Radial velocity (Rv) | −10.9 km/s |
| Proper motion (μ) | RA: −121.17 mas/yr Dec.: −14.91 mas/yr |
| Parallax (π) | 31.38 ± 0.24 mas |
| Distance | 103.9 ± 0.8 ly (31.9 ± 0.2 pc) |
| Absolute magnitude (MV) | −0.67 |
| Details | |
| Mass | 6.1±0.1 M☉ |
| Radius | 3.4 R☉ |
| Luminosity | 594±31 L☉ |
| Surface gravity (log g) | 3.78 cgs |
| Temperature | 15,540±1,157 K |
| Rotational velocity (v sin i) | 150 km/s |
| Age | 10.0±2.6 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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