Epsilon Draconis

{{Short description|Binary star in the constellation Draco}} {{Starbox begin}} {{Starbox image | image= {{Location mark | image=Draco constellation map.svg | float=center | width=250 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=Epsilon Dra | x%=16.6 | y%=40.6 }} | caption=Location of ε Draconis (circled) }} {{Starbox observe 2s | epoch = J2000 | constell = [[Draco (constellation)|Draco]] | component1 = A | ra1 = {{RA|19|48|10.35046}}<ref name=GaiaDR3a/> | dec1 = {{DEC|+70|16|04.5491}}<ref name=GaiaDR3a/> | appmag_v1 = 3.91<ref name=SIMBADa/> | component2 = B | ra2 = {{RA|19|48|10.54875}}<ref name=GaiaDR3b/> | dec2 = {{DEC|+70|16|07.5676}}<ref name=GaiaDR3b/> | appmag_v2 = 6.80<ref name=SIMBADb/> }} {{Starbox character | component1 = A | type = [[red clump]]<ref name=kaler/> | class = G7IIIbFe-1<ref name=Keenan_McNeil_1989>{{cite journal | bibcode=1989ApJS...71..245K | title=The Perkins catalog of revised MK types for the cooler stars | journal=Astrophysical Journal Supplement Series | volume=71 | pages=245 | last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C. | year=1989 | doi=10.1086/191373 }} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=III/150&Name=HD%20188119 Epsilon Draconis' database entry] at [[VizieR]].</ref> | b-v = +0.88 <ref name="MERMILLIOD">{{cite journal| author=Mermilliod, J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV Data. SIMBAD | year=1986 | bibcode=1986EgUBV........0M}}</ref> | u-b = +0.48<ref name="MERMILLIOD"/> | variable = | component2 = B | b-v2 = 0.57<ref name=SIMBADb/> | class2 = F6V<ref name="Eggleton & Tokovinin 2008"/> }} {{Starbox astrometry | component1 = A | radial_v = {{val|+2.89|0.11}}<ref name=GaiaDR3a/> | prop_mo_ra = +79.486 | prop_mo_dec = +40.041 | pm_footnote = <ref name=GaiaDR3a/> | parallax = 21.3219 | p_error = 0.1256 | parallax_footnote = <ref name=GaiaDR3a/> | component2 = B | radial_v2 = | prop_mo_ra2 = +86.898 | prop_mo_dec2 = +37.126 | pm_footnote2 = <ref name=GaiaDR3b/> | parallax2 = 21.3808 | p_error2 = 0.0403 | parallax_footnote2 = <ref name=GaiaDR3b/> }} {{Starbox detail | component1 = A | mass = {{val|1.20|0.08}},<ref name=HD-TESS/> {{val|1.76|0.29|0.23}}<ref name=Luck2015/> | radius = {{val|10.41|0.29}}<ref name=HD-TESS/> | luminosity = 63.1<ref name=Luck2015/> | temperature = {{Val|4966|41|fmt=commas}}<ref name=Tautvaisiene2020/> | metal = {{M/H|-0.31}}<ref name=HD-TESS/> | metal_fe = {{val|-0.30}}<ref name=SIMBADa/> | gravity = 2.61<ref name=Luck2015/> | rotational_velocity = {{Val|2.25|0.56}}<ref name=Strassmeier2023/> | age_gyr = {{val|2.6|1.8|1.6}}<ref name=Luck2015/> | component2 = B | radius2 = 1.16<ref name=GaiaDR2b/> | temperature2 = 6,936<ref name=GaiaDR2b/> | luminosity2 = 2.814<ref name=GaiaDR2b/> }} {{Starbox catalog | names = {{odlist | name=Tyl | B=ε Dra | F=63 Dra | HR=7582 | AG=+70°689 | BD=+69°1070 | HD=188119 | HIP=97433 | PLX=4689 | SAO=9540 | GC=27471 | CCDM=J19482+7016AB | 2MASS=J19481035+7016045 | IRAS=19483+7008 }}<ref name="SIMBADa"/> }} {{Starbox reference |Simbad=HD+188119}} {{Starbox end}}

'''Epsilon Draconis''', [[Romanization of Greek|Latinized]] from ε Draconis, is a [[binary star]]<ref name="Eggleton & Tokovinin 2008"/> in the [[constellation]] [[Draco (constellation)|Draco]], with a combined [[apparent magnitude]] of 3.84,<ref name=Ducati2002/> it is the [[list of stars in Draco|eleventh-brightest star]] in this rather faint constellation. This star along with [[Delta Draconis]] (Altais), [[Pi Draconis]] and [[Rho Draconis]] forms an [[asterism (astronomy)|asterism]] known as Al Tāis, meaning "the Goat".<ref>{{cite book | last=Allen | first=R. H. | year=1963 | author-link=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | url=https://archive.org/details/starnamestheirlo00alle/page/209 | access-date=2010-12-12 | edition=Reprint | publisher=Dover Publications Inc | location=New York, NY | isbn=0-486-21079-0 | page=[https://archive.org/details/starnamestheirlo00alle/page/209 209] | url-access=registration }}</ref> The distance to this system has been calculated to be about {{val|150|u=[[light-year]]s}}, based on [[stellar parallax]] measurements.<ref name=GaiaDR3a/>

In [[Chinese astronomy]], {{lang|zh|天廚}} ({{lang|zh-Latn|Tiān Chú}}), meaning the [[Purple Forbidden enclosure|Celestial Kitchen]], refers to an asterism consisting of Epsilon Draconis, [[Delta Draconis]], [[Sigma Draconis]], Rho Draconis, [[64 Draconis]] and Pi Draconis.<ref>{{in lang|zh}} ''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}}.</ref> Consequently, the [[Chinese star names|Chinese name]] for Epsilon Draconis itself is {{lang|zh|天廚三}} ({{lang|zh-Latn|Tiān Chú sān}}, {{langx|en|the Third Star of the Celestial Kitchen}}.)<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_t_z.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive |url=https://web.archive.org/web/20100819122914/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_t_z.htm |date=August 19, 2010 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref> Most authors do not use a traditional name for this star, using instead the [[Bayer designation]];<ref name=kaler>{{cite web |title=Epsilon Draconis |first=Jim|last=Kaler |url=http://stars.astro.illinois.edu/sow/epsdra.html |access-date=2016-11-24}}</ref> but [[Antonín Bečvář|Bečvář]] (1951) listed it as '''Tyl''' {{IPAc-en|'|t|I|l}}.<ref name=Kunitzsch>{{cite book |last1=Kunitzsch |first1=Paul |last2=Smart |first2=Tim |date = 2006 |edition = 2nd rev. |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations |publisher = Sky Pub |location = Cambridge, Massachusetts |isbn = 978-1-931559-44-7 }}</ref><ref>{{cite book |last=Bakich |first=Michael |date=1995 |title=The Cambridge Guide to the Constellations |url=https://archive.org/details/cambridgeguideto00baki |url-access=registration |quote=Tyl. |publisher=[[Cambridge University Press]] |page=[https://archive.org/details/cambridgeguideto00baki/page/202 202] |access-date=2016-11-24 |isbn=0521449219}}</ref>

== Visibility == With a declination in excess of 70 degrees north, Epsilon Draconis is principally visible in the northern hemisphere, with southern locations north of 20° South able to see it just above the horizon. The star is [[Circumpolar star|circumpolar]] throughout all of [[Europe]], [[China]], most of [[India]] and as far south as the tip of the [[Baja peninsula]] in [[North America]] as well as other locations around the globe having a latitude greater than about 20° North. Since Epsilon Draconis has an apparent magnitude of almost 4.0, the star is easily observable to the naked eye as long as one's stargazing is not hampered by the [[light pollution]] common to most cities.

The best time for observation is in the evening sky during the summer months, when the "Dragon constellation" passes the meridian at midnight, but given its circumpolar nature in the northern hemisphere, it is visible to most of the world's inhabitants throughout the year.

== Properties == Epsilon Draconis is a [[binary star]], whose components can be split in a telescope. They are separated by {{val|3.2|u=[[arcsec]]onds}} as of 2012, translating to a [[projected separation]] of {{val|145|u=[[astronomical unit]]s}}.<ref name=kaler/>

The primary of the system has a [[Stellar classification|spectral type]] of G7IIIbFe-1, which classify it as a is a [[Giant star|yellow giant]] star, a star which ran out of [[hydrogen]] at its [[stellar core|core]] and expanded in size.<ref name=Keenan_McNeil_1989/> It is visible with [[apparent magnitude]] of 3.91.<ref name=SIMBADa/> [[Asteroseismology]] of this star retrieve a mass of {{val|1.20|u=[[solar mass]]es}} and a radius over ten times [[solar radius|solar]].<ref name=HD-TESS/> Other estimates suggest masses between 1.5 and 2 solar masses.<ref name=Luck2015/> This star's abundance of elements heavier than [[helium]] relative to [[hydrogen]], what astronomers term [[metallicity]], is just half of the Sun's.<ref name=HD-TESS/>{{efn|name=metal}} The [[effective temperature]] of the star is {{val|4966|fmt=commas|ul=K}},<ref name=Tautvaisiene2020/> roughly 800 degrees cooler than the Sun. It seems to have already enabled helium fusion at its [[stellar core|core]], being a [[red clump]] star.<ref name=kaler/>

The secondary is a [[F-type main-sequence star]] of class F6V,<ref name="Eggleton & Tokovinin 2008"/> fusing hydrogen into helium at its core. It has an [[apparent magnitude]] 6.8<ref name=SIMBADb/> and is 14 times fainter than the primary. This star is about 20% times larger, three times brighter and about 1,100 degrees hotter than the Sun.<ref name=GaiaDR2b/>

== See also == * [[Variable star]] * [[Double star]]

==Notes== {{notelist|refs=

{{efn|name=metal|1 = The abundance is estimated by taking [M/H] to the power of ten:{{indent|10}}10<sup>[M/H]</sup> = 10<sup>−0.31</sup> = 0.49}}

}}

== References == <references> <ref name=Strassmeier2023>{{Cite journal |last1=Strassmeier |first1=K. G. |last2=Weber |first2=M. |last3=Gruner |first3=D. |last4=Ilyin |first4=I. |last5=Steffen |first5=M. |last6=Baratella |first6=M. |last7=Järvinen |first7=S. |last8=Granzer |first8=T. |last9=Barnes |first9=S. A. |last10=Carroll |first10=T. A. |last11=Mallonn |first11=M. |last12=Sablowski |first12=D. |last13=Gabor |first13=P. |last14=Brown |first14=D. |last15=Corbally |first15=C. |date=2023-03-01 |title=VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole - I. Survey design, pilot analysis, and initial data release |journal=[[Astronomy & Astrophysics]] |language=en |volume=671 |pages=A7 |doi=10.1051/0004-6361/202245255 |arxiv=2302.01794 |bibcode=2023A&A...671A...7S |issn=0004-6361}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/164/135&TIC=279979429 Epsilon Draconis' database entry] at [[VizieR]].</ref>

<ref name=Tautvaisiene2020>{{Cite journal |last1=Tautvaišienė |first1=G. |last2=Mikolaitis |first2=Š. |last3=Drazdauskas |first3=A. |last4=Stonkutė |first4=E. |last5=Minkevičiūtė |first5=R. |last6=Kjeldsen |first6=H. |last7=Brogaard |first7=K. |last8=von Essen |first8=C. |last9=Grundahl |first9=F. |last10=Pakštienė |first10=E. |last11=Bagdonas |first11=V. |last12=Viscasillas Vázquez |first12=C. |date=2020-05-01 |title=Chemical Composition of Bright Stars in the Continuous Viewing Zone of the TESS Space Mission |journal=[[The Astrophysical Journal Supplement Series]] |volume=248 |issue=1 |pages=19 |doi=10.3847/1538-4365/ab8b67 |doi-access=free |arxiv=2005.07526 |bibcode=2020ApJS..248...19T |issn=0067-0049}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/ApJS/248/19&TIC=279979429 Epsilon Draconis' database entry] at [[VizieR]].</ref>

<ref name=SIMBADa>{{cite simbad|title=eps Dra|access-date=January 26, 2025}}</ref>

<ref name=SIMBADb>{{cite simbad|title=eps Dra B|access-date=January 26, 2025}}</ref>

<ref name=HD-TESS>{{Cite journal |last1=Hon |first1=Marc |last2=Kuszlewicz |first2=James S. |last3=Huber |first3=Daniel |last4=Stello |first4=Dennis |last5=Reyes |first5=Claudia |date=2022-10-01 |title=HD-TESS: An Asteroseismic Catalog of Bright Red Giants within TESS Continuous Viewing Zones |journal=[[The Astronomical Journal]] |volume=164 |issue=4 |pages=135 |doi=10.3847/1538-3881/ac8931 |doi-access=free |arxiv=2208.06478 |bibcode=2022AJ....164..135H |issn=0004-6256}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/164/135&TIC=279979429 Epsilon Draconis' database entry] at [[VizieR]].</ref>

<ref name=Luck2015>{{Cite journal |last=Luck |first=R. Earle |date=2015-09-01 |title=Abundances in the Local Region. I. G and K Giants |journal=[[The Astronomical Journal]] |volume=150 |issue=3 |pages=88 |doi=10.1088/0004-6256/150/3/88 |arxiv=1507.01466 |bibcode=2015AJ....150...88L |issn=0004-6256}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/150/88&Name=*%20eps%20Dra Epsilon Draconis' database entry] at [[VizieR]].</ref>

<ref name=Ducati2002>{{Cite journal |last=Ducati |first=J. R. |date=2002-01-01 |title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system. |bibcode=2002yCat.2237....0D |journal=VizieR Online Data Catalog |volume=2237}}</ref>

<ref name="Eggleton & Tokovinin 2008">{{Cite journal |last1=Eggleton |first1=P. P. |last2=Tokovinin |first2=A. A. |date=2008-09-01 |title=A catalogue of multiplicity among bright stellar systems |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=389 |issue=2 |pages=869–879 |doi=10.1111/j.1365-2966.2008.13596.x |doi-access=free |arxiv=0806.2878 |bibcode=2008MNRAS.389..869E |issn=0035-8711}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/MNRAS/389/869&mHR=7582 Epsilon Draconis' database entry] at [[VizieR]].</ref>

== External links == *Astrophotographs:[http://www.asociacionhubble.org/portal/index.php/foro/viewtopic.php?f=63&t=16459&start=50 Epsilon Draconis] *SkyView Image: [http://skyview.gsfc.nasa.gov/cgi-bin/nnskcall.pl?VCOORD=297.0431337500000382,+70.2679302777777792&SURVEY=Digitized+Sky+Survey&SCOORD=&EQUINX=2000&LUT=colortables/stern-special.bin Epsilon Draconis] {{Stars of Draco}} {{Sky|19|48|10.35|+|70|16|04.55|100000}} {{Authority control}}

[[Category:G-type giants]] [[Category:Double stars]]  [[Category:Draco (constellation)]] [[Category:Bayer objects|Draconis, Epsilon]] [[Category:Durchmusterung objects|BD+69 1070]] [[Category:Flamsteed objects|Draconis, 63]] [[Category:Henry Draper Catalogue objects|188119]] [[Category:Hipparcos objects|097433]] [[Category:Bright Star Catalogue objects|7582]] [[Category:Stars with proper names|Tyl]] [[Category:Horizontal-branch stars]]