# Alpha Comae Berenices

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Star in the constellation Coma Berenices

α Comae Berenices α Comae Berenices (circled) in the constellation Coma Berenices Observation data Epoch J2000 Equinox J2000 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 Diadem, α Com, 42 Com, BD+18 2697, GC 17833, GJ 501, HIP 64241, SAO 100443, PPM 129630, ADS 8804, CCDM J13100+1732, WDS J13100+1732, LTT 13802, NLTT 33105, STF 1728, IDS 13051+1803 AB[6] A: HD 114378, HR 4968[12] B: HD 114379, HR 4969[13] Database references SIMBAD The system A B

**Alpha Comae Berenices** (**α Comae Berenices**, abbreviated **Alpha Com**, **α Com**) is a [binary star](/source/Binary_star) in the northern [constellation](/source/Constellation) of [Coma Berenices](/source/Coma_Berenices) ([Berenice](/source/Berenice_II_of_Egypt)'s Hair), 17.8 parsecs (58 ly) away. It consists of two [main sequence](/source/Main_sequence) stars, each a little hotter and more luminous than the Sun.

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/](https://en.wikipedia.org/wiki/Help:IPA/English), the traditional name for the system)[14] and B.

## Nomenclature

*α Comae Berenices* ([Latinised](/source/Latinisation_of_names) to *Alpha Comae Berenices*) is the system's [Bayer designation](/source/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](/source/Star_system), and adopted by the [International Astronomical Union](/source/International_Astronomical_Union) (IAU).[15]

The system has the proper name *Diadem*, of unknown modern origin.[4] In 2016, the [International Astronomical Union](/source/International_Astronomical_Union) organized a [Working Group on Star Names](/source/IAU_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](/source/Multiple_star).[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](/source/Chinese_astronomy), 太微左垣 (*Tài Wēi Zuǒ Yuán*), meaning *[Left Wall of Supreme Palace Enclosure](/source/Supreme_Palace_enclosure)*, refers to an [asterism](/source/Asterism_(astronomy)) consisting of Alpha Comae Berenices, [Eta Virginis](/source/Eta_Virginis), [Gamma Virginis](/source/Gamma_Virginis), [Delta Virginis](/source/Delta_Virginis) and [Epsilon Virginis](/source/Epsilon_Virginis).[18] Consequently, the [Chinese name](/source/Chinese_star_names) 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]

## Properties

Although Alpha Comae Berenices bears the title "[alpha](/source/Alpha)", at [magnitude](/source/Apparent_magnitude) 4.32 it is actually fainter than [Beta Comae Berenices](/source/Beta_Comae_Berenices).

It is a [binary star](/source/Binary_star), with almost equal components of magnitudes 5.05 m and 5.08 m [orbiting](/source/Orbit) each other with a [period](/source/Orbital_period) of 25.87 years. The system, estimated to be 58 [light-years](/source/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. If eclipses do occur, the next [primary eclipse](/source/Primary_eclipse) is expected to be around 27 September 2040; the next date for a [secondary eclipse](/source/Secondary_eclipse), which has only a 3.3% probability of happening, is 11 January 2026.[8]

The mean separation between them is approximately 10 [AU](/source/Astronomical_unit), about the distance between the Sun and [Saturn](/source/Saturn).

The binary star has a [visual companion](/source/Double_star), CCDM J13100+1732C, of apparent magnitude 10.2, located 89 [arcseconds](/source/Arcsecond) away along a position angle of 345°.[22]

Alpha Comae Berenicis forms an isosceles triangle with globular star clusters [Messier 53](/source/Messier_53) and [NGC 5053](/source/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.

## References

1. ^ [***a***](#cite_ref-van_Leeuwen2007_1-0) [***b***](#cite_ref-van_Leeuwen2007_1-1) [***c***](#cite_ref-van_Leeuwen2007_1-2) [***d***](#cite_ref-van_Leeuwen2007_1-3) [***e***](#cite_ref-van_Leeuwen2007_1-4) van Leeuwen, F. (2007). ["Validation of the new Hipparcos reduction"](http://www.aanda.org/articles/aa/abs/2007/41/aa8357-07/aa8357-07.html). *Astronomy and Astrophysics*. **474** (2): 653–664. [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357). [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600). [Vizier catalog entry](http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=64022)

1. **[^](#cite_ref-nsv1_2-0)** NSV 6116, database entry, [New Catalogue of Suspected Variable Stars, the improved version](http://www.sai.msu.su/groups/cluster/gcvs/gcvs/nsv/nsv.dat), Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 3, 2008.

1. **[^](#cite_ref-orb_3-0)** Entry 13100+1732, [Sixth Catalog of Orbits of Visual Binary Stars](http://ad.usno.navy.mil/wds/orb6/orb6orbits.txt) [Archived](https://web.archive.org/web/20050424035159/http://ad.usno.navy.mil/wds/orb6/orb6orbits.txt) 2005-04-24 at the [Wayback Machine](/source/Wayback_Machine), [United States Naval Observatory](/source/United_States_Naval_Observatory). Accessed on line September 3, 2008.

1. ^ [***a***](#cite_ref-kaler_4-0) [***b***](#cite_ref-kaler_4-1) [Kaler, Jim](/source/Jim_Kaler) (2008-05-11). ["Diadem"](http://stars.astro.illinois.edu/sow/diadem.html).

1. ^ [***a***](#cite_ref-bsc2_5-0) [***b***](#cite_ref-bsc2_5-1) [HR 4968](http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/50/catalog&recno=4968), database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., [CDS](/source/Centre_de_Donn%C3%A9es_astronomiques_de_Strasbourg) ID [V/50](http://vizier.u-strasbg.fr/viz-bin/Cat?V/50). Accessed on line September 3, 2008.

1. ^ [***a***](#cite_ref-sb0_6-0) [***b***](#cite_ref-sb0_6-1) [***c***](#cite_ref-sb0_6-2) [***d***](#cite_ref-sb0_6-3) [NSV 6116 -- Variable Star](https://simbad.u-strasbg.fr/simbad/sim-id?Ident=alf+com), database entry, [SIMBAD](/source/SIMBAD). Accessed on line September 3, 2008.

1. **[^](#cite_ref-Reiners2006_7-0)** Reiners, Ansgar (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", *Astronomy and Astrophysics*, **446** (1): 267–277, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0509399](https://arxiv.org/abs/astro-ph/0509399), [Bibcode](/source/Bibcode_(identifier)):[2006A&A...446..267R](https://ui.adsabs.harvard.edu/abs/2006A&A...446..267R), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20053911](https://doi.org/10.1051%2F0004-6361%3A20053911), [S2CID](/source/S2CID_(identifier)) [8642707](https://api.semanticscholar.org/CorpusID:8642707)

1. ^ [***a***](#cite_ref-Muterspaugh2015_8-0) [***b***](#cite_ref-Muterspaugh2015_8-1) 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](/source/ArXiv_(identifier)):[1501.05639](https://arxiv.org/abs/1501.05639). [Bibcode](/source/Bibcode_(identifier)):[2015AJ....150..140M](https://ui.adsabs.harvard.edu/abs/2015AJ....150..140M). [doi](/source/Doi_(identifier)):[10.1088/0004-6256/150/5/140](https://doi.org/10.1088%2F0004-6256%2F150%2F5%2F140). [S2CID](/source/S2CID_(identifier)) [119282868](https://api.semanticscholar.org/CorpusID:119282868).

1. ^ [***a***](#cite_ref-pavlovic_9-0) [***b***](#cite_ref-pavlovic_9-1) Pavlovic, R.; Todorovic, N. (2005). ["Orbits of Seven Edge-On Visual Double Stars"](https://doi.org/10.2298%2FSAJ0570073P). *Serbian Astronomical Journal*. **170** (170): 73–78. [Bibcode](/source/Bibcode_(identifier)):[2005SerAJ.170...73P](https://ui.adsabs.harvard.edu/abs/2005SerAJ.170...73P). [doi](/source/Doi_(identifier)):[10.2298/SAJ0570073P](https://doi.org/10.2298%2FSAJ0570073P).

1. ^ [***a***](#cite_ref-brummelaar_10-0) [***b***](#cite_ref-brummelaar_10-1) [***c***](#cite_ref-brummelaar_10-2) Ten Brummelaar, Theo; Mason, Brian D.; McAlister, Harold A.; Roberts, Lewis C.; Turner, Nils H.; Hartkopf, William I.; Bagnuolo, William G. (2000). ["Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory"](https://doi.org/10.1086%2F301338). *The Astronomical Journal*. **119** (5): 2403. [Bibcode](/source/Bibcode_(identifier)):[2000AJ....119.2403T](https://ui.adsabs.harvard.edu/abs/2000AJ....119.2403T). [doi](/source/Doi_(identifier)):[10.1086/301338](https://doi.org/10.1086%2F301338).

1. ^ [***a***](#cite_ref-pastel_11-0) [***b***](#cite_ref-pastel_11-1) [***c***](#cite_ref-pastel_11-2) Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". *Astronomy and Astrophysics*. **591**: A118. [arXiv](/source/ArXiv_(identifier)):[1605.07384](https://arxiv.org/abs/1605.07384). [Bibcode](/source/Bibcode_(identifier)):[2016A&A...591A.118S](https://ui.adsabs.harvard.edu/abs/2016A&A...591A.118S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201628497](https://doi.org/10.1051%2F0004-6361%2F201628497). [S2CID](/source/S2CID_(identifier)) [119258214](https://api.semanticscholar.org/CorpusID:119258214).

1. **[^](#cite_ref-12)** [HD 114378 -- Star in double system](https://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+114378), database entry, [SIMBAD](/source/SIMBAD), accessed on line September 3, 2008.

1. **[^](#cite_ref-13)** [HD 114379 -- Star in double system](https://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+114379), database entry, [SIMBAD](/source/SIMBAD), accessed on line September 3, 2008.

1. ^ [***a***](#cite_ref-IAU-LSN_14-0) [***b***](#cite_ref-IAU-LSN_14-1) ["Naming Stars"](https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/). IAU.org. Archived from [the original](https://www.iau.org/public/themes/naming_stars/) on 10 March 2025. Retrieved 16 December 2017.

1. **[^](#cite_ref-planetnaming_15-0)** 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](/source/ArXiv_(identifier)):[1012.0707](https://arxiv.org/abs/1012.0707) [[astro-ph.SR](https://arxiv.org/archive/astro-ph.SR)].

1. **[^](#cite_ref-16)** ["International Astronomical Union | IAU"](https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/). *www.iau.org*. Archived from [the original](https://www.iau.org/science/scientific_bodies/working_groups/280/) on 2016-06-10. Retrieved 2017-03-31.

1. **[^](#cite_ref-TriRpt18_17-0)** ["WG Triennial Report (2015-2018) - Star Names"](https://ghostarchive.org/archive/20221009/https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf) (PDF). p. 5. Archived from [the original](https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf) (PDF) on 2022-10-09. Retrieved 2018-07-14.

1. **[^](#cite_ref-18)** (in Chinese) *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](/source/ISBN_(identifier)) [978-986-7332-25-7](https://en.wikipedia.org/wiki/Special:BookSources/978-986-7332-25-7).

1. **[^](#cite_ref-19)** (in Chinese) [香港太空館 - 研究資源 - 亮星中英對照表](http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_c_d.htm) [Archived](https://web.archive.org/web/20090929163750/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_c_d.htm) 2009-09-29 at the [Wayback Machine](/source/Wayback_Machine), Hong Kong Space Museum. Accessed on line November 23, 2010.

1. **[^](#cite_ref-20)** (in Chinese) [English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name](http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#SupremePalaceEnclosure) [Archived](https://web.archive.org/web/20080924022136/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm) 2008-09-24 at the [Wayback Machine](/source/Wayback_Machine), Hong Kong Space Museum. Accessed on line November 23, 2010.

1. **[^](#cite_ref-21)** [Richard Hinckley Allen: Star Names — Their Lore and Meaning: Coma Berenices](https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Coma_Berenices*.html)

1. **[^](#cite_ref-wds_22-0)** Entry 13100+1732, discoverer code STF1728, components AB-C, [The Washington Double Star Catalog](http://ad.usno.navy.mil/wds/wdsnewframe3.html) [Archived](https://web.archive.org/web/20080413021643/http://ad.usno.navy.mil/wds/wdsnewframe3.html) 2008-04-13 at the [Wayback Machine](/source/Wayback_Machine), [United States Naval Observatory](/source/United_States_Naval_Observatory). Accessed on line September 3, 2008.

## External links

v t e Constellation of Coma Berenices List of stars in Coma Berenices Coma Berenices in Chinese astronomy Stars Bayer α (Diadem) β γ Flamsteed 7 11 12 13 14 16 17 21 23 (Phyllon Kissinou) 24 31 35 36 37 41 Variable FK GP IN LW HR 4668 HD 107146 108863 108874 110067 114762 b 115404 116029 Other 2MASS J12195156+3128497 KELT-6 WASP-56 WISE 1217+1626 Exoplanets HD 108874 b c KELT-6b Star clusters Coma Star Cluster Messier 53 NGC 4147 NGC 5053 Nebulae LoTr 5 Galaxies Messier 64 (Black Eye Galaxy) 85 88 91 98 99 100 NGC 4014 4015 4017 4053 4056 4060 4061 4065 4066 4070 4072 4074 4076 4084 4086 4089 4090 4091 4092 4093 4095 4098 4136 4146 4150 4162 4185 4189 4203 4211 4212 4213 4222 4237 4245 4253 4262 4274 4278 4293 4298 4302 4308 4310 4312 4314 4323 4328 4340 4359 4375 4383 4393 4394 4414 4419 4448 4450 4455 4459 4468 4473 4474 4475 4477 4479 4489 4494 4495 4498 4502 4506 4515 4516 4523 4525 4540 4555 4556 4558 4559 4561 4565 4571 4585 4595 4611 4614 4615 4633 4634 4651 4659 4670 4673 4676 (Mice Galaxies) 4689 4692 4710 4712 4725 4747 4839 4848 4860 4869 4871 4872 4873 4874 4875 4876 4881 4883 4886 4889 4892 4895 4907 4911 4919 4921 4944 5000 5004 5012 5032 5056 5172 Other 3C 275.1 3C 287 Arp 60 Coma Berenices Dragonfly 44 IC 755 (NGC 4019) IC 831 IC 860 IC 3505 IC 3528 IC 4040 IC 4051 IOK-1 IRAS F12032+1707 LEDA 83677 M85-HCC1 Malin 1 PGC 44691 PKS 1155+251 PKS 1222+216 VIRGOHI21 ZwCl 1305.4+2941 BCG Galaxy clusters Abell 1413 Coma I Coma Cluster Coma Supercluster M94 Group NGC 4065 Group NGC 4631 Group Astronomical events GRB 050509B iPTF14atg SN 1940B SN 1979C SN 2005ap SN 2006X SN 2020oi Category

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Adapted from the Wikipedia article [Alpha Comae Berenices](https://en.wikipedia.org/wiki/Alpha_Comae_Berenices) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Alpha_Comae_Berenices?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.