{{Short description|Star in the constellation Draco}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Draco constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=τ Draconis |x=255|y=440 }} | caption = Location of τ Draconis (circled in red) }} {{Starbox observe | epoch = [[J2000.0]] | equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]]) | constell = [[Draco (constellation)|Draco]] | ra = {{RA|19|15|33.05868}}<ref name=vanLeeuwen2007/> | dec = {{DEC|+73|21|19.6769}}<ref name=vanLeeuwen2007/> | appmag_v = 4.45<ref name=Johnson1966/> }} {{Starbox character | class = K2 III:<ref name=Luck2015/> | b-v = +1.25<ref name=Johnson1966/> | u-b = +1.45<ref name=Johnson1966/> | r-i = | variable = }} {{Starbox astrometry | radial_v = −33.70<ref name=Luck2015/> | prop_mo_ra = −115.29<ref name=vanLeeuwen2007/> | prop_mo_dec = +103.23<ref name=vanLeeuwen2007/> | parallax = 22.28 | p_error = 0.50 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = +1.19<ref name=Anderson2012/> | absmag_bol = }} {{Starbox detail | source = | mass = 1.25<ref name=Luck2015/> | radius = | luminosity = 48<ref name=Luck2015/> | temperature = {{Val|4413|77|fmt=commas}}<ref name=Luck2015/> | gravity = 2.00<ref name=Mishenina1995/> | metal_fe = {{Val|0.17|0.06}}<ref name=Taylor2002/> | rotational_velocity = 8<ref name=Bernacca1970/> | age_gyr = 6.48<ref name=Luck2015/> }} {{Starbox catalog | names = {{odlist|B=τ Dra | F=60 Dra | BD=+73°857 | FK5=729 | HD=181984 | HIP=94648 | HR=7352 | SAO=9366 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = tau+Dra }} {{Starbox end}} '''Tau Draconis''', [[Latinisation of names|Latinized]] from '''τ Draconis''', is an [[astrometric binary]]<ref name=Eggleton2008/> [[star]] system in the northern [[circumpolar constellation]] of [[Draco (constellation)|Draco]]. The star is faintly visible to the naked eye, having an [[apparent visual magnitude]] of 4.45.<ref name=Johnson1966/> Based upon an annual [[stellar parallax|parallax shift]] of 22.28 [[milliarcsecond|mas]] as measured from Earth,<ref name=vanLeeuwen2007/> it is located around 146 [[light year]]s from the [[Sun]]. Its [[proper motion]] is propelling it across the sky at the rate of 0.176 [[arc second]]s per year.<ref name=Lepine2005/>
This is a [[K-type star|K-type]] [[giant star]] with a [[stellar classification]] of K2 III:,<ref name=Luck2015/> where the semi-colon indicates some uncertainty about its spectral value. It is considered [[Metallicity|metal-rich]]<ref name=Taylor2002/> star and is past the first [[dredge-up]] phase of its post-[[main sequence]] [[stellar evolution|evolution]], although it shows under-abundances of carbon and oxygen in its [[spectrum]].<ref name=Mishenina1995/> The star has 1.25<ref name=Luck2015/> times the [[mass of the Sun]] and is an estimated 6.48<ref name=Luck2015/> billion years old. It is radiating 48<ref name=Luck2015/> times the [[solar luminosity]] from its enlarged [[photosphere]] at an [[effective temperature]] of 4,413 K.<ref name=Luck2015/>
==References== <references> <ref name=vanLeeuwen2007>{{citation | title=Validation of the new Hipparcos reduction | last1=van Leeuwen | first1=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}</ref>
<ref name=Anderson2012>{{citation | 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 | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | s2cid=119257644 | postscript=. }}</ref>
<ref name=Taylor2002>{{citation | title=A statistical search for supermetallicity in F, G and K stars | last1=Taylor | first1=B. J. | postscript=. | journal=Monthly Notices of the Royal Astronomical Society | volume=329 | issue=4 | pages=839–847 | date=February 2002 | doi=10.1046/j.1365-8711.2002.05046.x | bibcode=2002MNRAS.329..839T | doi-access=free }}</ref>
<ref name=Eggleton2008>{{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=Lepine2005>{{citation | 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 | postscript=. }}</ref>
<ref name=Luck2015>{{citation | title=Abundances in the Local Region. I. G and K Giants | last1=Luck | first1=R. Earle | journal=The Astronomical Journal | volume=150 | issue=3 | id=88 | pages=23 | date=September 2015 | doi=10.1088/0004-6256/150/3/88 | bibcode=2015AJ....150...88L | arxiv=1507.01466 | s2cid=118505114 | postscript=. }}</ref>
<ref name=Mishenina1995>{{citation | title=Chemical composition of five giants with positive CN-indices. | display-authors=1 | last1=Mishenina | first1=T. V. | last2=Kutsenko | first2=S. V. | last3=Musaev | first3=F. A. | journal=Astronomy and Astrophysics Supplement | volume=113 | page=333 | date=October 1995 | bibcode=1995A&AS..113..333M | postscript=. }}</ref>
<ref name=Bernacca1970>{{citation | last1=Bernacca | first1=P. L. | last2=Perinotto | first2=M. | title=A catalogue of stellar rotational velocities | journal=Contributi Osservatorio Astronomico di Padova in Asiago | volume=239 | issue=1 | year=1970 | page=1 | bibcode=1970CoAsi.239....1B | postscript=. }}</ref>
<ref name=Johnson1966>{{citation | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | year=1966 | page=99 | bibcode=1966CoLPL...4...99J | postscript=. }}</ref>
<ref name=SIMBAD>{{cite simbad | title=tau Dra | accessdate=2017-05-30 | postscript=. }}</ref> </references>
{{Stars of Draco|state=collapsed}}
[[Category:K-type giants]] [[Category:Draco (constellation)]] [[Category:Bayer objects|Draconis, Tau]] [[Category:Durchmusterung objects|BD+73 0857]] [[Category:Flamsteed objects|Draconis, 60]] [[Category:Henry Draper Catalogue objects|181984]] [[Category:Hipparcos objects|094648]] [[Category:Bright Star Catalogue objects|7352]] [[Category:Astrometric binaries]]