Alpha Comae Berenices (α Comae Berenices, abbreviated Alpha Com, α Com) is a binary star in the constellation of Coma Berenices (Berenice's Hair), 17.8 parsecs (58 ly) away. It consists of two main sequence stars, each a little hotter and more luminous than the Sun.
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Coma Berenices |
Right ascension | 13h 09m 59.285s[1] |
Declination | +17° 31′ 46.04″[1] |
Apparent magnitude (V) | 4.29 to 4.35 (combined)[2] A: 4.85 / B: 5.53[3] |
Characteristics | |
Spectral type | A: F5V / B: F5V (binary star)[4] |
U−B color index | −0.06[5] |
B−V color index | 0.45[5] |
V−R color index | 0.2[6] |
R−I color index | 0.2[6] |
Astrometry | |
Radial velocity (Rv) | −17.7±0.9[6] km/s |
Proper motion (μ) | RA: −433.13±0.70[1] mas/yr Dec.: 141.24±0.51[1] mas/yr |
Parallax (π) | 56.10 ± 0.89 mas[1] |
Distance | 58.1 ± 0.9 ly (17.8 ± 0.3 pc) |
Absolute magnitude (MV) | 3.82[7] |
Orbit[8] | |
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° |
Details | |
A | |
Mass | 1.237[9] M☉ |
Luminosity | 1.72[10] L☉ |
Surface gravity (log g) | 4.19[11] cgs |
Temperature | 6,365[11] K |
Metallicity [Fe/H] | −0.23[11] dex |
B | |
Mass | 1.087[9] M☉ |
Luminosity | 1.75[10] L☉ |
Temperature | 6,378[10] K |
Other designations | |
A: HD 114378, HR 4968 | |
B: HD 114379, HR 4969 | |
Database references | |
SIMBAD | data |
Alpha Comae Berenices is said to represent the crown worn by Queen Berenice. The two components are designated Alpha Comae Berenices A (officially named Diadem /ˈdaɪədɛm/, the traditional name for the system)[14] and B.
α Comae Berenices (Latinised to Alpha Comae Berenices) is the system's Bayer designation. The designations of the two components as Alpha Comae Berenices A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[15]
The system bore the traditional names Diadem and Al Dafirah, the latter derived from the Arabic الضفيرة ađ̧-đ̧afīrah "the braid".[citation needed] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[17] It approved the name Diadem for the component Alpha Comae Berenices A on 1 February 2017 and it is now so included in the List of IAU-approved Star Names.[14]
In Chinese, 太微左垣 (Tài Wēi Zuǒ Yuán), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of Alpha Comae Berenices, Eta Virginis, Gamma Virginis, Delta Virginis and Epsilon Virginis.[18] Consequently, the Chinese name for Alpha Comae Berenices itself is 太微左垣五 (Tài Wēi Zuǒ Yuán wǔ, English: the Fifth Star of Left Wall of Supreme Palace Enclosure.),[19] representing 東上將 (Dōngshǎngjiāng), meaning The First Eastern General.[20] 東上將 (Dōngshǎngjiāng), westernized into Shang Tseang, but that name was designated for "v Comae Berenices" by R.H. Allen and the meaning is "a Higher General".[21]
Although Alpha Comae Berenices bears the title "alpha", at magnitude 4.32 it is actually fainter than Beta Comae Berenices.
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.[8]
The mean separation between them is approximately 10 AU, about the distance between the Sun and Saturn.
The binary star has a visual companion, CCDM J13100+1732C, of apparent magnitude 10.2, located 89 arcseconds away along a position angle of 345°.[22]
Alpha Comae Berenicis forms an isosceles triangle with globular star clusters Messier 53 and NGC 5053. The apparent diameter of this triangle is a little more than one degree. The location of Alpha Comae Berenicis is westward (preceding) of both globular star clusters.