Alpha Comae Berenices
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Coma Berenices |
| Right ascension | 13h 09m 59.285s |
| Declination | +17° 31′ 46.04″ |
| Apparent magnitude (V) | 4.29 to 4.35 (combined) A: 4.85 / B: 5.53 |
| Characteristics | |
| Spectral type | A: F5V / B: F5V (binary star) |
| U−B color index | −0.06 |
| B−V color index | 0.45 |
| V−R color index | 0.2 |
| R−I color index | 0.2 |
| Astrometry | |
| Radial velocity (Rv) | −17.7±0.9 km/s |
| Proper motion (μ) |
RA: −433.13±0.70 mas/yr Dec.: 141.24±0.51 mas/yr |
| Parallax (π) | 56.10 ± 0.89mas |
| Distance | 58.1 ± 0.9 ly (17.8 ± 0.3 pc) |
| Absolute magnitude (MV) | 3.82 |
| Orbit | |
| Period (P) | 25.8696±0.008219 yr |
| Semi-major axis (a) | 0.67144±0.00033" |
| Eccentricity (e) | 0.51060±0.00061 |
| Inclination (i) | 90.0501±0.0062° |
| Longitude of the node (Ω) | 12.2272±0.0098° |
| Periastron epoch (T) | 57056.84±0.36 |
|
Argument of periastron (ω) (secondary) |
100.563±0.026° |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alpha Comae Berenices (Alpha Com, α Com, α Comae Berenices) is a star in the constellation Coma Berenices (Berenice's Hair). Although it has the Bayer designation "alpha", at magnitude 4.32 it is actually fainter than Beta Comae Berenices. It has the traditional name Diadem. It is said to represent the crown worn by Queen Berenice. A name occasionally seen is Al Dafirah, from the Arabic الضفيرة ađ̧-đ̧afīrah "the braid".
In Chinese, 太微左垣 (Tài Wēi Zuǒ Yuán), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of α Comae Berenices, η Virginis, γ Virginis, δ Virginis and ε Virginis. Consequently, α Comae Berenices itself is known as 太微左垣五 (Tài Wēi Zuǒ Yuán wǔ, English: the Fifth Star of Left Wall of Supreme Palace Enclosure.), representing 東上將 (Dōngshǎngjiāng), meaning The First Eastern General. 東上將 (Dōngshǎngjiāng), westernized into Shang Tseang, but the name Shang Tseang was designated for "v Comae Berenices" by R.H. Allen and the meaning is "a Higher General"
It is a binary star, with almost equal components of magnitudes 5.05 m and 5.08 m orbiting each other with a period of 25.87 years. The system, estimated to be 58 light years distant, appears so nearly "edge-on" from the Earth that the two stars appear to move back-and-forth in a straight line with a maximum separation of only 0.7 arcsec. Eclipses are predicted to occur between the two components however they have not been successfully observed due to miscalculations of the time of eclipse.
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