Alcor (star)
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 |
| Proper motion (μ) | RA: +120.21 mas/yr Dec.: −16.04 mas/yr |
| 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 | 1.842+0.027 −0.031 M☉ |
| Radius | 2.002+0.068 −0.067 (equatorial) 1.723±0.050 (polar) R☉ |
| Luminosity | 13.98±0.75 L☉ |
| Surface gravity (log g) | 4.25 cgs |
| Temperature | 7,556+109 −123 (equator) 8,985+116 −124 (polar) K |
| Rotational velocity (v sin i) | 239+10 −13 km/s |
| Age | 422+67 −75 Myr |
| Alcor B | |
| Mass | 0.25 M☉ |
| Age | 500±100 Myr |
| Other designations | |
| g Ursae Majoris, 80 Ursae Majoris, BD+55 1603, CCDM J13240+5456D, GC 18155, HD 116842, HIP 65477, HR 5062, PPM 34021, SAO 28751, WDS J13239+5456C | |
| Database references | |
| SIMBAD | data |
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 lie about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite.