Alpha Cephei
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Cepheus |
| Right ascension | 21h 18m 34.8s |
| Declination | +62° 35′ 08.0″ |
| Apparent magnitude (V) | 2.45 |
| Characteristics | |
| Spectral type | A7 IV |
| U-B color index | 0.12 |
| B-V color index | 0.22 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | -11.5 km/s |
| Proper motion (μ) | RA: 149.91 mas/yr Dec.: 48.27 mas/yr |
| Parallax (π) | 66.84 ± 0.49 mas |
| Distance | 48.8 ± 0.4 ly (15 ± 0.1 pc) |
| Absolute magnitude (MV) | 1.57 |
| Details | |
| Mass | 1.9 M☉ |
| Radius | 2.5 R☉ |
| Luminosity | 18 L☉ |
| Temperature | 7,600 K |
| Metallicity | ? |
| Rotation | 246 km/s. |
| Age | ? years |
| Other designations | |
Alpha Cephei (α Cep / α Cephei) is a star in the constellation of Cepheus. It also has the traditional name Alderamin.
Alderamin is an A-type star, evolving off of the main sequence into a subgiant, likely on its way to becoming a red giant as its hydrogen supply runs low. Alderamin is noted for having an unusually fast rotation, though the effects of this rotation are not well understood.
The name Alderamin is a contraction of the Arabic phrase الذراع اليمين að-ðirā‘ al-yamīn "the right arm," with the first definite article transliterated literally as al, as is often the case with Arabic star names. It is known as 天鈎五 (the Fifth Star of the Celestial Hook) in Chinese.
This star is located near the precessional path traced across the celestial sphere by the Earth's north pole. That means that periodically this star comes within 3° of being a pole star, much as Polaris is at present. This will next occur about the year 7500 A.D.
[edit] See also
| Preceded by Iota Cephei |
Pole Star 6800–? |
Succeeded by Deneb? |
 |
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