Theta Draconis

{{short description|Binary star system in the constellation Draco}} {{Starbox begin | name = θ 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=θ Draconis |x=580|y=846 }} | caption = Location of θ Draconis (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|16|01|53.34636}}<ref name="LEEUWEN"/> | dec = {{DEC|+58|33|54.9056}}<ref name="LEEUWEN"/> | appmag_v = 4.000<ref name=ubvp>{{cite journal|bibcode=1993A&AS..100..591O}}</ref> | constell = [[Draco (constellation)|Draco]] }} {{Starbox character | type = | class = F9 V<ref name=Abt2009/> or F8IV-V<ref name=Tokovinin_et_al_2006/><ref name=Mazeh_et_al_1992/> | b-v = {{val|+0.528|0.013}}<ref name=Anderson_Francis_2012/> | u-b = +0.11<ref name="MERMILLIOD"/> | variable = }} {{Starbox astrometry | radial_v = {{val|−8.23|0.20}}<ref name=Anderson_Francis_2012/> | prop_mo_ra = −319.51<ref name="LEEUWEN"/> | prop_mo_dec = 334.97<ref name="LEEUWEN"/> | parallax = 47.54 | p_error = 0.12 | parallax_footnote = <ref name="LEEUWEN"/> | absmag_v = 2.39<ref name=Earle2017/> }} {{Starbox orbit | reference = <ref name=Mazeh_et_al_2002/> | period_unitless = {{val|3.0708216|0.0000069|u=days|fmt=commas}} | axis_unitless = ~{{convert|0.048|AU|solar radius|abbr=on}}<ref name=Heacox1999/> | eccentricity = {{val|0.039|0.012}} | inclination =  | node =  | periastron = {{val|5971.98|0.13|fmt=commas}} | periarg = {{val|63|15}} | k1 = {{val|25.10|0.31}} | k2 = {{val|66.0|2.2}} }} {{Starbox detail | source = <ref name=Earle2017/> | component1 = A | mass = {{val|1.53|u=solar mass}}<ref name=Earle2017/> {{val|1.2|0.1|u=solar mass}}<ref name=Mazeh_et_al_2002/> 1.18<ref name=Tokovinin_et_al_2006/> | radius = {{val|2.83|0.12|0.05}}<ref name=GaiaDR2/> | luminosity = {{Val|9.998|0.137}}<ref name=GaiaDR2/> | temperature = {{val|6105|53|129|fmt=commas}}<ref name=GaiaDR2/> | gravity = 3.79 | metal_fe = +0.19 | rotational_velocity = 30.7 | age_gyr = 2.03 | component2 = B | mass2 = {{val|0.46|0.04|u=solar mass}}<ref name=Mazeh_et_al_2002/> 0.21<ref name=Tokovinin_et_al_2006/> }} {{Starbox catalog | names = {{odlist | B=θ Dra | F=13 Her | BD=+58°1608 | FK5=598 | HD=144284 | HIP=78527 | HR=5986 | SAO=29765 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=tet+Dra }} {{Starbox end}}

'''Theta Draconis''', a name [[Romanization of Greek|Latinized]] from θ Draconis, is a [[binary star]] system in the northern [[circumpolar constellation]] of [[Draco (constellation)|Draco]]. It is faintly visible to the naked eye at night with an [[apparent visual magnitude]] of almost exactly 4.<ref name=ubvp/> [[Stellar parallax|Parallax]] measurements place it at an estimated distance of {{Convert|68.6|ly|pc|abbr=off|lk=on}} from the [[Sun]],<ref name="LEEUWEN"/> and it is drifting closer with a [[radial velocity]] of −8 km/s.<ref name=Anderson_Francis_2012/> It has a relatively high [[proper motion]], traversing the [[celestial sphere]] at the rate of {{val|0.464|u=arcsecond}} per year.<ref name=Lepine_Shara_2005/> [[Olin J. Eggen|O. J. Eggen]] included this star as a member of the [[NGC 1901]] supercluster based on its space motion.<ref name=eggen1996/>

The binary nature of this system was discovered by [[William Wallace Campbell|W. W. Campbell]] in 1899, and the first set of [[orbital elements]] was published by [[Heber Doust Curtis|H. D. Curtis]] in 1907.<ref name=Curtis1907/> It is a single-lined [[spectroscopic binary]] in a close orbit with a [[orbital period|period]] of 3.07 days and an [[orbital eccentricity|eccentricity]] (ovalness) of 0.04.<ref name=Abt2009/> The secondary component has been resolved in the [[infrared astronomy|infrared]] [[H band (infrared)|H band]], allowing an estimation of the mass ratio as {{val|0.38|0.03}}.<ref name=Mazeh_et_al_2002/> Some velocity variation of [[semi-amplitude|K1]] was observed by M. Mayor and T. Mazeh in 1987, which is suggestive of a tertiary component to the system.<ref name=Mayor_Mazeh_1987/>

The primary component is a [[solar-type star]]<ref name=Mazeh_et_al_1992/> that at various times has been assigned [[stellar classification]]s of F9 V<ref name=Abt2009/> and F8IV-V.<ref name=Tokovinin_et_al_2006/> The star is about two billion years old and is spinning with a [[projected rotational velocity]] of 31 km/s.<ref name=Earle2017/> It has a high [[metallicity]] (heavy element abundances) with around 20%<ref name=Mazeh_et_al_2002/> more mass than the Sun and nearly three<ref name=GaiaDR2/> times the Sun's radius. The star displays no [[Chromosphere|chromospheric]] emission and may be on or entering the [[subgiant star|subgiant stage]]. Because of the close orbit, it could be filling up to 60% of its [[Roche lobe]].<ref name=Young_Koniges_1977/> The star is radiating ten times the luminosity of the Sun from its [[photosphere]] at an [[effective temperature]] of {{val|6105|u=K|fmt=commas}}.<ref name=GaiaDR2/>

==Chinese name== 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 consisting of θ Draconis, [[Iota Draconis|ι Draconis]], [[Eta Draconis|η Draconis]], [[Zeta Draconis|ζ Draconis]], [[Upsilon Draconis|υ Draconis]], [[73 Draconis]], [[Gamma Cephei|γ Cephei]] and [[23 Cassiopeiae]].<ref name=zh/> Consequently, the [[Chinese star names|Chinese name]] for θ Draconis itself is {{lang|zh|紫微左垣二}} ({{lang|zh-Latn|Zǐ Wēi Zuǒ Yuán èr}}, {{langx|en|the Second Star of Left Wall of Purple Forbidden Enclosure}}.),<ref name=AEEA/> representing {{lang|zh|上宰}} ({{lang|zh-Latn|Shǎngzǎi}}), meaning ''The First Premier''.<ref name=LCSD/> 上宰 (Shǎngzǎi) is westernized into ''Shang Tsae'' by R.H. Allen with meaning "the Minor Steward" but it was for [[Eta Draconis|η Dra]] (Aldibain).<ref name=Allen1963/>

== References == <references> <ref name=SIMBAD>{{cite simbad | title=tet Dra | access-date=2021-01-10 }}</ref>

<ref name=Young_Koniges_1977>{{cite journal | title=A study of the occurrence of singly ionized calcium emission in late-type spectroscopic binary stars. | last1=Young | first1=A. | last2=Koniges | first2=A. | journal=Astrophysical Journal | volume=211 | pages=836–843 | date=February 1977 | doi=10.1086/154992 | bibcode=1977ApJ...211..836Y | doi-access=free }}</ref>

<ref name=Mayor_Mazeh_1987>{{cite journal | title=The frequency of triple and multiple stellar systems. | last1=Mayor | first1=M. | last2=Mazeh | first2=T. | journal=Astronomy and Astrophysics | volume=171 | pages=157–177 | date=January 1987 | bibcode=1987A&A...171..157M }}</ref>

<ref name=Mazeh_et_al_1992>{{cite journal | title=On the Mass-Ratio Distribution of Spectroscopic Binaries with Solar-Type Primaries | last1=Mazeh | first1=Tsevi | last2=Goldberg | first2=Dorit | last3=Duquennoy | first3=Antoine | last4=Mayor | first4=Michel | display-authors=1 | journal=Astrophysical Journal | volume=401 | page=265 | date=December 1992 | doi=10.1086/172058 | bibcode=1992ApJ...401..265M }}</ref>

<ref name=eggen1996>{{cite journal | title=The Stellar Content of Star Stream I | last=Eggen | first=Olin J. | journal=Astronomical Journal | volume=111 | pages=1615 | year=1996 | bibcode=1996AJ....111.1615E | doi=10.1086/117901 }}</ref>

<ref name=Heacox1999>{{cite journal | title=On the Nature of Low-Mass Companions to Solar-like Stars | last=Heacox | first=William D. | journal=The Astrophysical Journal | volume=526 | issue=2 | pages=928–936 | date=December 1999 | doi=10.1086/308033 | bibcode=1999ApJ...526..928H | doi-access=free }}</ref>

<ref name=Lepine_Shara_2005>{{cite journal | last1=Lépine | first1=Sébastien | last2=Shara | first2=Michael M. | title=A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog) | journal=The Astronomical Journal | volume=129 | issue=3 | pages=1483–1522 | date=March 2005 | doi=10.1086/427854 | bibcode=2005AJ....129.1483L | arxiv=astro-ph/0412070 | s2cid=2603568 }}</ref>

<ref name=Tokovinin_et_al_2006>{{cite journal | title=Tertiary companions to close spectroscopic binaries | last1=Tokovinin | first1=A. | last2=Thomas | first2=S. | last3=Sterzik | first3=M. | last4=Udry | first4=S. | display-authors=1 | journal=Astronomy and Astrophysics | volume=450 | issue=2 | pages=6811–693 |date=May 2006 | bibcode=2006A&A...450..681T | arxiv=astro-ph/0601518 | doi=10.1051/0004-6361:20054427 | s2cid=8899546 }}</ref>

<ref name=Abt2009>{{cite journal | last=Abt | first=Helmut A. | title=MK Classifications of Spectroscopic Binaries | journal=The Astrophysical Journal Supplement | volume=180 | issue=1 | pages=117–18 | date=2009 | doi=10.1088/0067-0049/180/1/117 | bibcode=2009ApJS..180..117A | s2cid=122811461 }}</ref>

<ref name=Anderson_Francis_2012>{{cite journal | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 }}</ref>

<ref name=Earle2017>{{cite journal | title=Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants | last1=Luck | first1=R. Earle | journal=The Astronomical Journal | volume=153 | issue=1 | id=21 | pages=19 | date=January 2017 | bibcode=2017AJ....153...21L | arxiv=1611.02897 | doi=10.3847/1538-3881/153/1/21 | s2cid=119511744 | doi-access=free }}</ref>

<ref name=Curtis1907>{{cite journal | title=Orbit of the spectroscopic binary theta Draconis | last=Curtis | first=H. D. | journal=Astrophysical Journal | volume=26 | pages=263−267 | date=November 1907 | doi=10.1086/141500 | bibcode=1907ApJ....26..263C | s2cid=222445276 | doi-access=free }}</ref>

<ref name=Mazeh_et_al_2002>{{cite journal | title=Infrared Detection of Low-Mass Secondaries in Spectroscopic Binaries | last1=Mazeh | first1=Tsevi | last2=Prato | first2=L. | last3=Simon | first3=M. | last4=Goldberg | first4=Elad | last5=Norman | first5=Dara | last6=Zucker | first6=Shay | display-authors=1 | journal=The Astrophysical Journal | volume=564 | issue=2 | pages=1007–1014 | date=January 2002 | doi=10.1086/324404 | arxiv=astro-ph/0110536 | bibcode=2002ApJ...564.1007M | s2cid=12431948 }}</ref>

<ref name="LEEUWEN">{{cite journal | title=Hipparcos, the New Reduction | last=van Leeuwen | first=F. |date=November 2007 | pages=653–664 | issue=2 | volume=474 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V | arxiv=0708.1752 | doi=10.1051/0004-6361:20078357 | s2cid=18759600 | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%2078527 | access-date=2010-11-21 }}</ref>

<ref name="MERMILLIOD">{{cite journal |bibcode=1986EgUBV........0M |title=Compilation of Eggen's UBV data, transformed to UBV (Unpublished) |last1=Mermilliod |first1=J. -C |journal=Catalogue of Eggen's UBV Data |year=1986 }}</ref>

<ref name=zh>{{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>

<ref name=AEEA>{{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>

<ref name=LCSD>{{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/20080924022136/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure |date=2008-09-24 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>

<ref name=Allen1963>{{cite web | url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html | work=Star Names, their Lore and Meaning | title=Draco, the Dragon | page=210 | edition=Dover | first=R. H. | last=Allen | year=1963 | access-date=2021-01-11 }}</ref> </references>

==External links== *{{cite web | title=THETA DRA (Theta Draconis) | work=Stars | publisher=University of Illinois | first=James B. | last=Kaler | url=http://stars.astro.illinois.edu/sow/thetadra.html | access-date=2010-11-21}}

{{Stars of Draco}} {{Sky|16|01|53.35|+|58|33|54.90|1000000}}  [[Category:F-type main-sequence stars]] [[Category:Spectroscopic binaries]]  [[Category:Draco (constellation)]] [[Category:Bayer objects|Draconis, Theta]] [[Category:Durchmusterung objects]] [[Category:Flamsteed objects|Draconis, 13]] [[Category:Henry Draper Catalogue objects|144284]] [[Category:Hipparcos objects|078527]] [[Category:Bright Star Catalogue objects|5986]]