# 21 Comae Berenices

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Star in the constellation Coma Berenices

21 Comae Berenices A visual band light curve for UU Comae Berenices from MOST data. Adapted from Paunzen et al. (2019)[1] Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Coma Berenices Right ascension 12h 31m 00.561s[2] Declination +24° 34′ 01.80″[2] Apparent magnitude (V) 5.41 – 5.46[3] Characteristics Evolutionary stage main sequence[1] Spectral type A3p SrCr[4] B−V color index 0.056±0.008[5] Variable type α2 CVn[1] + δ Sct[3] Astrometry Radial velocity (Rv) +1.0±1.8[5] km/s Proper motion (μ) RA: −12.474 mas/yr[2] Dec.: −9.085 mas/yr[2] Parallax (π) 12.0785±0.1214 mas[2] Distance 270 ± 3 ly (82.8 ± 0.8 pc) Absolute magnitude (MV) 0.66[5] Details[1] Mass 2.29±0.10 M☉ Radius 2.6±0.2 R☉ Luminosity 38.2±1.3 L☉ Surface gravity (log g) 3.9±0.2 cgs Temperature 8,900±200 K Rotation 2.05219 d Rotational velocity (v sin i) 63±2 km/s Age 400–800 Myr Other designations Kissīn[6], 21 Com, UU Com, BD+25°2517, HD 108945, HIP 61071, HR 4766, SAO 82346[7] Database references SIMBAD data

**21 Comae Berenices** is a [variable star](/source/Variable_star) in the northern [constellation](/source/Constellation) of [Coma Berenices](/source/Coma_Berenices).[8] It has the [variable star designation](/source/Variable_star_designation) UU Comae Berenices, while 21 Comae Berenices is the [Flamsteed designation](/source/Flamsteed_designation).[7][8][9]

## About

According to [R. H. Allen](/source/Richard_Hinckley_Allen), English [orientalist](/source/Oriental_studies) [Thomas Hyde](/source/Thomas_Hyde) attributed the ancient title Kissīn to this star, a name that comes from a climbing plant – either [bindweed](/source/Convolvulus) or [dog rose](/source/Dog_rose).[6] This star has a white hue and is just visible to the [naked eye](/source/Naked_eye) with an [apparent visual magnitude](/source/Apparent_visual_magnitude) that fluctuates at about 5.4.[3] Based upon [parallax](/source/Stellar_parallax) measurements, it is located at a distance of approximately 270 [light years](/source/Light_year) away from the Sun.[2] It is a single star but is a confirmed physical member of the [Melotte 111](/source/Coma_Star_Cluster) [open cluster](/source/Open_cluster).[10]

## History

This object has been studied extensively since 1953, producing some occasionally contradictory results such as hints of [pulsational behavior](/source/Pulsating_variable) or a [binary companion](/source/Spectroscopic_binary). It is a weakly magnetic [chemically peculiar](/source/Chemically_peculiar_star) star of type CP2, or [Ap star](/source/Ap_and_Bp_stars), that is most likely on the [main sequence](/source/Main_sequence).[1] The [stellar classification](/source/Stellar_classification) is A3p SrCr,[4] where the suffix notation indicates abundance anomalies of the [iron-peak element](/source/Iron-peak_element) chromium, as well as strontium.

In 1950, [Olin Jeuck Eggen](/source/Olin_J._Eggen) reported that the brightness of 21 Comae Berenices is variable.[11] This is an [Alpha2 Canum Venaticorum (ACV) variable](/source/Alpha2_Canum_Venaticorum_variable), which indicates it varies in luminosity as it rotates due to [spots](/source/Star_spot) on its surface created by a [magnetic field](/source/Stellar_magnetic_field). The range of variation has an [amplitude](/source/Amplitude) of 0.02 magnitude and a period of just over two days.[1] Samus et al. (2017) have it classified as a low-amplitude [Delta Scuti variable](/source/Delta_Scuti_variable),[3] although this is disputed.[1]

The age of the Melotte 111 cluster, and therefore this star, lies in the range of 400–800 million years. The star has a [projected rotational velocity](/source/Projected_rotational_velocity) of 63 km/s, with a polar inclination of 64° or greater, resulting in a rotation period of 2.05 days. Stellar evolutionary models yield a mass of around 2.3 times that of the Sun and 2.6 times the [Sun's radius](/source/Sun's_radius) for this object. It is radiating 38 times the [luminosity of the Sun](/source/Luminosity_of_the_Sun) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 8,900 K.[1]

## References

1. ^ [***a***](#cite_ref-Paunzen2019_1-0) [***b***](#cite_ref-Paunzen2019_1-1) [***c***](#cite_ref-Paunzen2019_1-2) [***d***](#cite_ref-Paunzen2019_1-3) [***e***](#cite_ref-Paunzen2019_1-4) [***f***](#cite_ref-Paunzen2019_1-5) [***g***](#cite_ref-Paunzen2019_1-6) [***h***](#cite_ref-Paunzen2019_1-7) Paunzen, Ernst; et al. (May 2019), "A revisit to the enigmatic variable star 21 Comae", *Monthly Notices of the Royal Astronomical Society*, **485** (3): 4247–4259, [arXiv](/source/ArXiv_(identifier)):[1904.04809](https://arxiv.org/abs/1904.04809), [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.485.4247P](https://ui.adsabs.harvard.edu/abs/2019MNRAS.485.4247P), [doi](/source/Doi_(identifier)):[10.1093/mnras/stz413](https://doi.org/10.1093%2Fmnras%2Fstz413), [S2CID](/source/S2CID_(identifier)) [104292433](https://api.semanticscholar.org/CorpusID:104292433).

1. ^ [***a***](#cite_ref-GaiaDR3_2-0) [***b***](#cite_ref-GaiaDR3_2-1) [***c***](#cite_ref-GaiaDR3_2-2) [***d***](#cite_ref-GaiaDR3_2-3) [***e***](#cite_ref-GaiaDR3_2-4) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D3959965486205062528%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Samus2017_3-0) [***b***](#cite_ref-Samus2017_3-1) [***c***](#cite_ref-Samus2017_3-2) [***d***](#cite_ref-Samus2017_3-3) Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", *Astronomy Reports*, **61** (1): 80, [Bibcode](/source/Bibcode_(identifier)):[2017ARep...61...80S](https://ui.adsabs.harvard.edu/abs/2017ARep...61...80S), [doi](/source/Doi_(identifier)):[10.1134/S1063772917010085](https://doi.org/10.1134%2FS1063772917010085), [S2CID](/source/S2CID_(identifier)) [125853869](https://api.semanticscholar.org/CorpusID:125853869).

1. ^ [***a***](#cite_ref-Renson2009_4-0) [***b***](#cite_ref-Renson2009_4-1) Renson, P.; Manfroid, J. (2009), "Catalogue of Ap, HgMn and Am stars", *Astronomy and Astrophysics*, **498** (3): 961–966, [Bibcode](/source/Bibcode_(identifier)):[2009A&A...498..961R](https://ui.adsabs.harvard.edu/abs/2009A&A...498..961R), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/200810788](https://doi.org/10.1051%2F0004-6361%2F200810788).

1. ^ [***a***](#cite_ref-Anderson2012_5-0) [***b***](#cite_ref-Anderson2012_5-1) [***c***](#cite_ref-Anderson2012_5-2) Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *Astronomy Letters*, **38** (5): 331, [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971), [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A), [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644)

1. ^ [***a***](#cite_ref-Allen1963_6-0) [***b***](#cite_ref-Allen1963_6-1) Allen, Richard Hinckley (1963), [*Star Names: Their Lore and Meaning*](https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Coma_Berenices*.html), Dover Publications Inc., p. 171, retrieved 2019-11-01.

1. ^ [***a***](#cite_ref-Simbad_7-0) [***b***](#cite_ref-Simbad_7-1) ["21 Com"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=21+Com). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2019-11-01.

1. ^ [***a***](#cite_ref-:0_8-0) [***b***](#cite_ref-:0_8-1) ["21 Comae Berenices - Star in Coma Berenices | TheSkyLive.com"](https://theskylive.com/sky/stars/21-comae-berenices-star). *theskylive.com*. Retrieved 2023-06-13.

1. **[^](#cite_ref-9)** Guide, Universe (25 January 2015). ["21 Comae Berenices Star Facts"](https://www.universeguide.com/star/61071/21comaeberenices). *Universe Guide*. Retrieved 13 June 2023.

1. **[^](#cite_ref-Silaj2014_10-0)** Silaj, J.; Landstreet, J. D. (2014), "Accurate age determinations of several nearby open clusters containing magnetic Ap stars", *Astronomy & Astrophysics*, **566**: A132, [arXiv](/source/ArXiv_(identifier)):[1407.4531](https://arxiv.org/abs/1407.4531), [Bibcode](/source/Bibcode_(identifier)):[2014A&A...566A.132S](https://ui.adsabs.harvard.edu/abs/2014A&A...566A.132S), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201321468](https://doi.org/10.1051%2F0004-6361%2F201321468), [S2CID](/source/S2CID_(identifier)) [53370832](https://api.semanticscholar.org/CorpusID:53370832).

1. **[^](#cite_ref-Eggen1950_11-0)** Eggen, Olin J. (July 1950). ["Photoelectric Studies.IV. Color-Luminosity Array for Stars in the Region of the Sun"](https://articles.adsabs.harvard.edu/pdf/1950ApJ...112..141E). *Astrophysical Journal*. **112**: 141–177. [Bibcode](/source/Bibcode_(identifier)):[1950ApJ...112..141E](https://ui.adsabs.harvard.edu/abs/1950ApJ...112..141E). [doi](/source/Doi_(identifier)):[10.1086/145324](https://doi.org/10.1086%2F145324). Retrieved 8 February 2025.

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 [21 Comae Berenices](https://en.wikipedia.org/wiki/21_Comae_Berenices) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/21_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.