{{Short description|Star in the constellation Coma Berenices}} {{Starbox begin}} {{Starbox image | image= {{Location mark |image=Coma Berenices constellation map.svg|alt=|float=center|width=260 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=12 Comae Berenices |x=510|y=304 }} |caption=Location of 12 Comae Berenices (circled in red) }} {{Starbox observe | epoch = J2000.0 | constell = [[Coma Berenices]] | ra = {{RA|12|22|30.31076}}<ref name=GaiaDR2/> | dec = {{DEC|+25|50|46.1896}}<ref name=GaiaDR2/> | appmag_v = 4.80<ref name=Griffin2011/> }} {{Starbox character | class = {{nowrap|G7 III + A3 V}}<ref name=Lam/> | b-v = 0.82/0.11<ref name=Griffin2011/> | u-b = 0.47/0.09<ref name=Griffin2011/> | variable = }} {{Starbox astrometry | radial_v = {{Val|+0.5|0.9}}<ref name=rgcrv/> | prop_mo_ra = −10.847<ref name=GaiaDR2/> | prop_mo_dec = −9.546<ref name=GaiaDR2/> | parallax = 11.8280 | p_error = 0.2353 | parallax_footnote = <ref name=GaiaDR2/> | absmag_v = {{nowrap|{{Val|0.55|0.06}} / {{Val|1.05|0.06}}}}<ref name=Griffin2011/> }} {{Starbox orbit | reference = <ref name=Lam/> | period_unitless = {{Val|396.4473|0.0002|u=days}} | eccentricity = {{Val|0.599483|0.000026}} | inclination = {{Val|64.8556|0.0011}} | periastron = {{Val|46877.148|0.054|u=[[Modified Julian day|MJD]]}} | periarg_primary = {{Val|100.162|0.001}} | k1 = {{Val|22.42|2.22}} | axis_unitless = {{val|20.3358|0.00066}} | node = {{val|118.618|0.004}} }} {{Starbox detail | source = | component1 = 12 Com A | mass = {{Val|2.64|0.07}}<ref name=Lam/> | radius = {{Val|8.36|0.15}}<ref name=Lam/> | temperature = {{Val|5300|200|fmt=commas}}<ref name=Griffin2011/> | luminosity = {{Val|56.2|2.7|2.5}}<ref name=Griffin2011/> | gravity = | metal_fe = | rotational_velocity = | age_myr = 533 ± 41 ± 42<ref name=Lam/> | component2 = 12 Com B | mass2 = {{Val|2.10|0.03}}<ref name=Lam/> | radius2 = {{Val|2.5|0.3}}<ref name=Griffin2011/> | temperature2 = {{Val|8500|500|fmt=commas}}<ref name=Griffin2011/> | luminosity2 = {{Val|30.2|2.2|2.2}}<ref name=Griffin2011/> }} {{Starbox catalog | names={{odlist | F=12 Com | BD=+26°2337 | FK5=1318 | HD=107700 | HIP=60351 | HR=4707 | SAO=82273 | WDS=J12225+2551A | NSV=5581 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=12+Com }} {{Starbox end}}
[[Image:12 Comae Berenices.jpg|thumb|left|12 Comae Berenices in optical light]] '''12 Comae Berenices''' is a [[binary star]] system in the northern [[constellation]] of [[Coma Berenices]]. It is the brightest member of the [[Coma Star Cluster]] and is visible to the naked eye with an [[apparent visual magnitude]] of 4.80.<ref name=Griffin2011/> Although listed as a suspected [[variable star]], there is no [[Photometry (astronomy)|photometric]] evidence of it being variable in luminosity. However, the [[radial velocity]] was found to be variable, as announced by [[William Wallace Campbell|W. W. Campbell]] in 1910. The first orbital solution was published by [[Julie Vinter Hansen|Vinter Hansen]] in the 1940s.<ref name=Griffin2011/> It is a double-lined [[spectroscopic binary]] with an [[orbital period]] of 396.5 days and an [[orbital eccentricity|eccentricity]] of 0.566.<ref name=mermilliod2007/>
This system consists of two [[star]]s, an [[stellar evolution|evolved]] [[G-type star|G-type]] [[giant star]] and a smaller but higher temperature [[A-type main-sequence star]].<ref name=Abt2008/> Griffin and Griffin (2011) suggested that the secondary component may have begun its evolution away from the main sequence, and instead assigned it a [[luminosity class]] of IV. The primary, designated component A, has about 2.6 times the [[mass of the Sun]] and has expanded to 8.4 times the [[Sun's radius]]. It is radiating 56 times the [[Sun's luminosity]] from its enlarged [[photosphere]] at an [[effective temperature]] of 5,300 K. Its companion, component B, has double the Sun's mass and 2.5 times the radius. It shines with 30 times the luminosity of the Sun at 8,500 K.<ref name=Griffin2011/>
==References== <references> <ref name=SIMBAD>{{cite simbad | title=12 Com | access-date=December 30, 2018 }}</ref>
<ref name=GaiaDR2>{{Cite Gaia DR2|4008342726516877312}}</ref>
<ref name=Griffin2011>{{citation | title=Composite spectra: XVII. 12 Comae, a member of the Coma open cluster | last1=Griffin | first1=R. E. M. | last2=Griffin | first2=R. F. | journal=Astronomische Nachrichten | volume=332 | issue=2 | pages=105–115 | date=February 2011 | doi=10.1002/asna.201011514 | bibcode=2011AN....332..105G | doi-access=free }}</ref>
<ref name=Abt2008>{{cite journal | last1=Abt | first1=Helmut A. | title=Visual Multiples. IX. MK Spectral Types | journal=The Astrophysical Journal Supplement Series | volume=176 | pages=216–217 | year=2008 | issue=1 | bibcode=2008ApJS..176..216A | doi=10.1086/525529 | doi-access=free }}</ref>
<ref name=mermilliod2007>{{cite journal | last1=Mermilliod | first1=J. -C | last2=Andersen | first2=J. | last3=Latham | first3=D. W. | last4=Mayor | first4=M. | title=Red giants in open clusters. XIII. Orbital elements of 156 spectroscopic binaries | display-authors=1 | journal=Astronomy and Astrophysics | volume=473 | issue=3 | pages=829 | year=2007 | bibcode=2007A&A...473..829M | doi=10.1051/0004-6361:20078007 | doi-access=free }}</ref>
<ref name=rgcrv>{{cite conference | last1=Evans | first1=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | contribution=The Revision of the General Catalogue of Radial Velocities | title=Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 | volume=30 | pages=57 | location=University of Toronto | publisher=[[International Astronomical Union]] | bibcode=1967IAUS...30...57E }}</ref>
<ref name=Lam>{{cite journal | doi=10.3847/1538-3881/accddb | doi-access=free | title=Precise Age for the Binary Star System 12 Com in the Coma Berenices Cluster | date=2023 | last1=Lam | first1=Rex | last2=Sandquist | first2=Eric L. | last3=Schaefer | first3=Gail H. | last4=Farrington | first4=Christopher D. | last5=Monnier | first5=John D. | last6=Anugu | first6=Narsireddy | last7=Lanthermann | first7=Cyprien | last8=Klement | first8=Robert | last9=Ennis | first9=Jacob | last10=Setterholm | first10=Benjamin R. | last11=Gardner | first11=Tyler | last12=Kraus | first12=Stefan | last13=Davies | first13=Claire L. | last14=Orosz | first14=Jerome A. | journal=The Astronomical Journal | volume=166 | issue=1 | page=29 | arxiv=2304.07397 | bibcode=2023AJ....166...29L }}</ref> </references>
{{Stars of Coma Berenices}}
[[Category:G-type giants]] [[Category:A-type main-sequence stars]] [[Category:Spectroscopic binaries]] [[Category:Coma Berenices]] [[Category:Durchmusterung objects]] [[Category:Flamsteed objects|Comae Berenices, 12]] [[Category:Henry Draper Catalogue objects|107700]] [[Category:Hipparcos objects|060351]] [[Category:Bright Star Catalogue objects|4707]]