Mu Cephei
Mu Cephei (Latinized from μ Cephei, abbreviated Mu Cep or μ Cep), also known as Herschel's Garnet Star, Erakis, or HD 206936, is a red supergiant or hypergiant star in the constellation Cepheus. It appears garnet red and is located at the edge of the IC 1396 nebula. Since 1943, the spectrum of this star has served as a spectral standard by which other stars are classified.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 43m 30.4609s |
| Declination | +58° 46′ 48.166″ |
| Apparent magnitude (V) | +4.08 (3.43 - 5.1) |
| Characteristics | |
| Evolutionary stage | Red supergiant or hypergiant |
| Spectral type | M2-Ia (M2e Ia) |
| U−B color index | +2.42 |
| B−V color index | +2.35 |
| Variable type | SRc |
| Astrometry | |
| Radial velocity (Rv) | +20.63 km/s |
| Proper motion (μ) | RA: 2.740±0.884 mas/yr Dec.: −5.941±0.922 mas/yr |
| Parallax (π) | 0.55 ± 0.20 mas |
| Distance | 3,060 ly (940+140 −40 pc) |
| Absolute magnitude (MV) | –7.63 |
| Details | |
| Mass | 19.2±0.1 M☉ |
| Radius | 972±228 (1,259 – 1,420) R☉ |
| Luminosity | 269,000+111,000 −40,000 (135,000 – 340,000) L☉ |
| Surface gravity (log g) | –0.36 – –0.5 cgs |
| Temperature | 3,551±136 (3,750 – 3,700) K |
| Age | 10.0±0.1 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Mu Cephei is more than 100,000 times brighter than the Sun, with an absolute visual magnitude of −7.6. It is also one of the largest known stars with a radius around or over 1,000 times that of the sun (R☉), and were it placed in the Sun's position it would engulf the orbit of Mars and Jupiter.
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