{{short description|Star in the constellation Draco}} {{Starbox begin | name = η Draconis }} {{Starbox image | image= {{Location mark |image=Draco constellation map.svg|alt=|float=center|width=260 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=η Draconis |x=514|y=784 }} |caption=Location of η Draconis (circled) }} {{Starbox observe | epoch = [[J2000.0]] | ra = {{RA|16|23|59.48594}}<ref name=aaa474_2_653/> | dec = {{DEC|+61|30|51.1699}}<ref name=aaa474_2_653/> | appmag_v = +2.73<ref name=pasj60_4_781/> | constell = [[Draco (constellation)|Draco]] }} {{Starbox character | class = G8 III<ref name=pasj60_4_781/> | b-v = +0.91<ref name=aass34_1/> | u-b = +0.70<ref name=aass34_1/> | variable = }} {{Starbox astrometry | radial_v = −14.3<ref name=gcsrv/> | prop_mo_ra = −17.02<ref name=aaa474_2_653/> | prop_mo_dec = +56.95<ref name=aaa474_2_653/> | parallax = 35.42 | p_error = 0.09 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = +0.58<ref name=aaa361_614/> }} {{Starbox detail | component1 = A | mass = {{val|2.55|0.26}}<ref name=rosas-portilla/> | radius = 10.46<ref name="gray2019"/>–10.53<ref name=Baines2018/> | gravity = {{val|2.82|0.11}}<ref name=rosas-portilla/> | metal_fe = −0.088<ref name="gray2019"/> | age_myr = {{val|650|100}}<ref name=Baines2018/> | luminosity = {{val|65.6|6.3}}<ref name=Baines2018/> | temperature = 5,018<ref name=gray2019/> | rotational_velocity = 8<ref name=coapa239_1/> | component2 = B | mass2 = 0.672<ref name=Hardegree-Ullman/> | radius2 = 0.577<ref name=Hardegree-Ullman/> | luminosity2 = 0.206<ref name=Hardegree-Ullman/> | temperature2 = 5,114<ref name=Hardegree-Ullman/> }} {{Starbox catalog | names = Aldibain, Athebyne, 14 Draconis, [[Bonner Durchmusterung|BD]]+61 1591, [[Catalogues of Fundamental Stars|FK5]] 822, [[Henry Draper catalogue|HD]] 148387, [[Hipparcos catalogue|HIP]] 80331, [[Harvard Revised catalogue|HR]] 6132, [[New Catalogue of Suspected Variable Stars|NSV]] 7713, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 17074, [[Washington Double Star Catalog|WDS]] 16240+6131.<ref name=SIMBAD/> }} {{Starbox reference |Simbad=eta+Dra }} {{Starbox end}} '''Eta Draconis''' ('''η Draconis''', abbreviated '''Eta Dra''', '''η Dra''') is a [[binary star]] in the northern [[circumpolar constellation]] of [[Draco (constellation)|Draco]]. Despite having an [[Apparent magnitude|apparent visual magnitude]] of only +2.73,<ref name=pasj60_4_781/> it is the [[List of stars in Draco|second-brightest star]] in this generally faint constellation. Based upon [[parallax]] measurements collected during the [[Hipparcos]] mission, this star is located at a distance of about {{Convert|92.1|ly|pc|abbr=off|lk=on}} from the [[Sun]].<ref name=aaa474_2_653/>
The two components are designated '''Eta Draconis A''' (also named '''Athebyne''' {{IPAc-en|'|æ|θ|ᵻ|b|aɪ|n}}<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars | publisher=IAU.org | access-date=16 December 2017 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref>) and '''B'''.
== Nomenclature ==
''η Draconis'' ([[Latinisation of names|Latinised]] to ''Eta Draconis'') is the system's [[Bayer designation]]. The designations of the two components as ''Eta Draconis A'' and ''B'' derives from the convention used by the Washington Multiplicity Catalog (WMC) for [[Star system|multiple star system]]s, and adopted by the [[International Astronomical Union]] (IAU).<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}</ref>
Eta Draconis, together with [[Zeta Draconis]], bore the traditional [[Arabic]] name الذئبين ''al-dhiʼbayn'', "the (two) wolves", lying in wait for the camel's foal, the little star [[Alruba|Al Rubaʽ]], protected by the [[Mother Camels]].<ref>[https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html Star Name - R.H Allen p. 202]</ref>
In 2016, the IAU organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN) | access-date=22 May 2016 | archive-date=10 June 2016 | archive-url=https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/ | url-status=dead }}</ref> to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire [[multiple star|multiple systems]].<ref name="TriRpt18">{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names | access-date=2018-07-14 | archive-date=2022-10-09 | archive-url=https://ghostarchive.org/archive/20221009/https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | url-status=dead }}</ref> It approved the name ''Athebyne'' (a rendering of ''adh-dhiʼbayn'') for the component Eta Draconis A on 5 September 2017. It approved the name ''Aldhibah'' (the female wolf) for Zeta Draconis A on the same date. Both are now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>
In [[Chinese astronomy|Chinese]], {{lang|zh|紫微左垣}} ({{lang|zh-Latn|Zǐ Wēi Zuǒ Yuán}}), meaning ''[[Purple Forbidden enclosure|Left Wall of Purple Forbidden Enclosure]]'', refers to an [[Asterism (astronomy)|asterism]] consisting of Eta Draconis, [[Iota Draconis]], [[Theta Draconis]], Zeta Draconis, [[Upsilon Draconis]], [[73 Draconis]], [[Gamma Cephei]] and [[23 Cassiopeiae]].<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 Eta Draconis itself is {{lang|zh|紫微左垣三}} ({{lang|zh-Latn|Zǐ Wēi Zuǒ Yuán sān}}, {{langx|en|the Third Star of Left Wall of Purple Forbidden Enclosure}}),<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0606/ap060610.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 10 日] {{Webarchive|url=https://web.archive.org/web/20110521234349/http://aeea.nmns.edu.tw/2006/0606/ap060610.html |date=2011-05-21 }}</ref> representing {{lang|zh|少宰}} ({{lang|zh-Latn|Shàozǎi}}), meaning ''The Second Premier''.<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name] {{webarchive |url=https://web.archive.org/web/20100810114313/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure |date=August 10, 2010 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref> Possibly, 少宰 (Shàozǎi) is westernized into ''Hea Tsae'' by R.H. Allen with meaning "the Lowest Steward" but it was for Theta Draconis.<ref>[https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html Star Name - R.H. Allen p. 210]</ref>
== Properties == Eta Draconis A is a star with 2.88<ref name="gray2019"/> times the [[Solar mass|mass of the Sun]]. The [[stellar spectrum|spectrum]] matches a [[stellar classification]] of G8 III,<ref name=pasj60_4_781/> with the [[Stellar classification#Yerkes spectral classification|luminosity class]] III indicating this is an [[stellar evolution|evolved]] [[giant star]] that has exhausted the supply of hydrogen at its core. It reached this stage in only 650<ref name=Baines2018/> million years because higher mass stars such as this consume the supply of hydrogen more rapidly than the Sun. The [[radius]] of Eta Draconis, as determined by its [[angular diameter]] and distance from Earth, is about 10.5 times the [[Solar radius|radius of the Sun]].<ref name="gray2019"/><ref name=Baines2018/> From its extended [[stellar atmosphere|envelope]], it is radiating around 65<ref name=Baines2018/> times the [[Solar luminosity|luminosity of the Sun]] at an [[effective temperature]] of 5,018 K,<ref name="gray2019"/> giving it the yellow glow of a G-type star.<ref name=csiro/>
Eta Draconis B is located at an [[Angular distance|angular separation]] of 5.1 [[Minute and second of arc|arcseconds]] from the primary. This is an 8.8 magnitude [[Stellar classification#Class K|K-type]] [[main sequence]] star with a stellar classification of K2 V.<ref name=mnras389_2_869/> At the estimated distance of this star system, the two stars are separated by a physical distance of at least 140 [[Astronomical unit|AU]] and require at least a millennium to complete an [[orbit]].<ref name=kaler/>
== References == <references> <ref name=Hardegree-Ullman>{{Cite journal |last1=Hardegree-Ullman |first1=Kevin K. |last2=Apai |first2=Dániel |last3=Bergsten |first3=Galen J. |last4=Pascucci |first4=Ilaria |last5=López-Morales |first5=Mercedes |date=2023-06-01 |title=Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets |bibcode=2023AJ....165..267H |journal=The Astronomical Journal |volume=165 |issue=6 |pages=267 |doi=10.3847/1538-3881/acd1ec |doi-access=free |arxiv=2304.12490 |issn=0004-6256}}</ref>
<ref name=aaa474_2_653>{{cite journal | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>
<ref name=Baines2018>{{cite journal | title=Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer | last1=Baines | first1=Ellyn K. | last2=Armstrong | first2=J. Thomas | last3=Schmitt | first3=Henrique R. | last4=Zavala | first4=R. T. | last5=Benson | first5=James A. | last6=Hutter | first6=Donald J. | last7=Tycner | first7=Christopher | last8=Belle | first8=Gerard T. van | display-authors=1 | journal=The Astronomical Journal | volume=155 | at=30 | year=2018 | issue=1 | arxiv=1712.08109 | bibcode=2018AJ....155...30B | doi=10.3847/1538-3881/aa9d8b | s2cid=119427037 | doi-access=free }}.</ref>
<ref name=rosas-portilla>{{Cite journal |last1=Rosas-Portilla |first1=F. |last2=Schröder |first2=K.-P. |last3=Jack |first3=D. |date=2022-04-26 |title=On the physical nature of the Wilson-Bappu effect: revising the gravity and temperature dependence |arxiv=2203.16593 |journal=Monthly Notices of the Royal Astronomical Society |volume=513 |issue=1 |pages=906–924 |doi=10.1093/mnras/stac929 |doi-access=free |issn=0035-8711}}</ref>
<ref name="gray2019">{{Cite journal |last1=Gray |first1=David F. |last2=Kaur |first2=Taranpreet |date=2019-09-01 |title=A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines |journal=The Astrophysical Journal |volume=882 |issue=2 |pages=148 |doi=10.3847/1538-4357/ab2fce |doi-access=free |bibcode=2019ApJ...882..148G |issn=0004-637X}}</ref>
<ref name=aaa361_614>{{cite journal | last1=Pizzolato | first1=N. | last2=Maggio | first2=A. | last3=Sciortino | first3=S. | title=Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases | journal=Astronomy and Astrophysics | volume=361 | pages=614–628 |date=September 2000 | bibcode=2000A&A...361..614P }}</ref>
<ref name=pasj60_4_781>{{cite journal | last1=Takeda | first1=Yoichi | last2=Sato | first2=Bun'ei | last3=Murata | first3=Daisuke | title=Stellar parameters and elemental abundances of late-G giants | journal=Publications of the Astronomical Society of Japan | volume=60 | issue=4 | pages=781–802 |date=August 2008 | bibcode=2008PASJ...60..781T |arxiv = 0805.2434 | doi=10.1093/pasj/60.4.781}}</ref>
<ref name=gcsrv>{{cite journal | last=Wilson | first=Ralph Elmer | date=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=[[Carnegie Institution of Washington]] | location=Washington | bibcode=1953GCRV..C......0W }}</ref>
<ref name=coapa239_1>{{cite journal | author=Bernacca, P. L. | author2=Perinotto, M. | title=A catalogue of stellar rotational velocities | journal=Contributi Osservatorio Astronomico di Padova in Asiago | volume=239 | issue=1 | date=1970 | page=1 | bibcode=1970CoAsi.239....1B }}</ref>
<ref name=aass34_1>{{cite journal | last1=Nicolet | first1=B. | date=1978 | title=Photoelectric photometric Catalogue of homogeneous measurements in the UBV System | journal=Astronomy and Astrophysics Supplement Series | volume=34 | pages=1–49 | bibcode=1978A&AS...34....1N }}</ref>
<ref name=mnras389_2_869>{{cite journal | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=389 | issue=2 | pages=869–879 |date=September 2008 | doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E |arxiv = 0806.2878 | s2cid=14878976 }}</ref>
<ref name=SIMBAD>{{cite simbad | title=eta Dra | access-date=2012-02-20 }}</ref>
<ref name=kaler>{{cite web | first1=James B. | last1=Kaler | work=Stars | title=AL DHIBAIN "PRIOR" (Eta Draconis) | publisher=[[University of Illinois]] | url=http://stars.astro.illinois.edu/sow/aldhibprior.html | access-date=2012-02-20 }}</ref>
<ref name=csiro>{{cite web |title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=[[Commonwealth Scientific and Industrial Research Organisation]] |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=2012-03-18 }}</ref> </references>
{{Stars of Draco}}
{{Authority control}}
[[Category:Draco (constellation)]] [[Category:Bayer objects|Draconis, Eta]] [[Category:G-type giants]] [[Category:Hipparcos objects|080331]] [[Category:Flamsteed objects|Draconis, 14]] [[Category:Henry Draper Catalogue objects|148387]] [[Category:Bright Star Catalogue objects|6132]] [[Category:Durchmusterung objects|BD+61 1591]] [[Category:Binary stars]] [[Category:Stars with proper names|Athebyne]] [[Category:Population I stars]]