Alpha Comae Berenices
| 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° |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alpha Comae Berenices (α Comae Berenices, abbreviated Alf Com, α Com) is a binary star in the constellation of Coma Berenices (Berenice's Hair). It is said to represent the crown worn by Queen Berenice.
The two components are designated Alpha Comae Berenices A (also named Diadem[11]) and B.
Nomenclature
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).[12]
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)[13] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[14] 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.[11]
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.[15] Consequently, Alpha 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.),[16] representing 東上將 (Dōngshǎngjiāng), meaning The First Eastern General.[17] 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".[18]
Properties
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°.[19]
References
- ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
- ^ NSV 6116, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 3, 2008.
- ^ Entry 13100+1732, Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory. Accessed on line September 3, 2008.
- ^ Diadem Archived 2008-05-11 at the Wayback Machine, Jim Kaler, Stars. Accessed on line September 3, 2008.
- ^ a b HR 4968, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 3, 2008.
- ^ a b c d NSV 6116 -- Variable Star, database entry, SIMBAD. Accessed on line September 3, 2008.
- ^ Reiners, A. (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics, 446 (1): 267–277, arXiv:astro-ph/0509399, Bibcode:2006A&A...446..267R, doi:10.1051/0004-6361:20053911.
- ^ a b Muterspaugh, Matthew W.; et al. (2015). "Predicting the α Comae Berenices Time of Eclipse: How 3 Ambiguous Measurements out of 609 Caused a 26 Year Binary's Eclipse to be Missed". The Astronomical Journal. 150 (5). 140. arXiv:1501.05639. Bibcode:2015AJ....150..140M. doi:10.1088/0004-6256/150/5/140.
- ^ HD 114378 -- Star in double system, database entry, SIMBAD, accessed on line September 3, 2008.
- ^ HD 114379 -- Star in double system, database entry, SIMBAD, accessed on line September 3, 2008.
- ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
- ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
- ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-03-31.
- ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
- ^ Template:Zh icon 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ^ Template:Zh icon 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2009-09-29 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ^ Template:Zh icon English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived 2008-09-24 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Coma Berenices
- ^ Entry 13100+1732, discoverer code STF1728, components AB-C, The Washington Double Star Catalog Archived 2008-04-13 at the Wayback Machine, United States Naval Observatory. Accessed on line September 3, 2008.
