Alcor (star)
Alcor (/ˈælkɔːr/) is a binary star system in the constellation of Ursa Major. It is the fainter companion of Mizar, the two stars forming a naked eye double in the handle of the Big Dipper (or Plough) asterism in Ursa Major. The two both lie about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite.
Location of Alcor (Mizar is circled, Alcor is invisible beside it at this scale) | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 13h 25m 13.53783s |
| Declination | +54° 59′ 16.6548″ |
| Apparent magnitude (V) | +3.99 |
| Characteristics | |
| Spectral type | A5Vn / M3-4 |
| Astrometry | |
| Radial velocity (Rv) | −9.6 km/s |
| Parallax (π) | 39.91 ± 0.13 mas |
| Distance | 81.7 ± 0.3 ly (25.06 ± 0.08 pc) |
| Absolute magnitude (MV) | +2.00 |
| Details | |
| Alcor A | |
| Mass | 1.84 M☉ |
| Radius | 1.846 R☉ |
| Luminosity | 14.03 L☉ |
| Surface gravity (log g) | 4.25 cgs |
| Temperature | 8,221 K |
| Rotational velocity (v sin i) | 228 km/s |
| Alcor B | |
| Mass | 0.25 M☉ |
| Age | 0.5 ± 0.1 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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