{{Short description|Variable star in the constellation Draco}} {{Starbox begin}} {{Starbox image | image= {{Location mark |image=Draco constellation map.svg |float=center |alt= |label= |position=right |width=320 |mark=Red circle.svg |mark_width=10 |mark_link=ο Draconis |x=118|y=721 }} |caption=Location of ο Dra (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|18|51|12.09530}}<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref> | dec = {{DEC|+59|23|18.0627}}<ref name=hipparcos/> | appmag_v = 4.65<ref name=hr>{{cite journal|bibcode=1991bsc..book.....H|title=The Bright star catalogue|journal=New Haven|last1=Hoffleit|first1=Dorrit|last2=Jaschek|first2=Carlos|year=1991}}</ref> | constell = [[Draco (constellation)|Draco]] }} {{Starbox character | class = G9III<ref name=perkins>{{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}}</ref> | b-v = | u-b = +1.19<ref name=hr/> | variable = [[RS Canum Venaticorum variable|RS CVn]] + [[eclipsing variable|eclipsing]]<ref name=orbit/> }} {{Starbox astrometry | radial_v = −19.52<ref>{{cite journal |last1=Karataș |first1=Yüksel |last2=Bilir |first2=Selçuk |last3=Eker |first3=Zeki |last4=Demircan |first4=Osman |last5=Liebert |first5=James |last6=Hawley |first6=Suzanne L. |last7=Fraser |first7=Oliver J. |last8=Covey |first8=Kevin R. |last9=Lowrance |first9=Patrick |last10=Kirkpatrick |first10=J. Davy |last11=Burgasser |first11=Adam J. |year=2004 |title=Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution |journal=Monthly Notices of the Royal Astronomical Society |volume=349 |issue=3 |pages=1069–1092 |arxiv=astro-ph/0404219 |bibcode=2004MNRAS.349.1069K |doi=10.1111/j.1365-2966.2004.07588.x |s2cid=15290475 |doi-access=free}}</ref> | prop_mo_ra = 77.47<ref name=hipparcos/> | prop_mo_dec = 25.37<ref name=hipparcos/> | parallax = 9.54 | p_error = 0.21 | parallax_footnote = <ref name=hipparcos/> | dist_ly = | dist_pc = 106.8<ref name=orbit/> | absmag_v = −0.344<ref name=BohmVitense2000/> }} {{Starbox orbit | reference = <ref name="orbit">{{cite journal |last1=Roettenbacher |first1=Rachael M. |last2=Monnier |first2=John D. |last3=Fekel |first3=Francis C. |last4=Henry |first4=Gregory W. |last5=Korhonen |first5=Heidi |last6=Latham |first6=David W. |last7=Muterspaugh |first7=Matthew W. |last8=Williamson |first8=Michael H. |last9=Baron |first9=Fabien |last10=Ten Brummelaar |first10=Theo A. |last11=Che |first11=Xiao |last12=Harmon |first12=Robert O. |last13=Schaefer |first13=Gail H. |last14=Scott |first14=Nicholas J. |last15=Sturmann |first15=Judit |year=2015 |title=Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries. II. O Draconis, a Candidate for Recent Low-mass Companion Ingestion |journal=The Astrophysical Journal |volume=809 |issue=2 |pages=159 |arxiv=1507.03601 |bibcode=2015ApJ...809..159R |doi=10.1088/0004-637X/809/2/159 |s2cid=119228345 |last16=Sturmann |first16=Laszlo |last17=Turner |first17=Nils H.}}</ref> | period = | period_unitless = {{val|138.444|0.003}} days | axis = {{val|0.00651|0.00003}} | axis_unitless = | eccentricity = {{val|0.158|0.003}} | inclination = {{val|89.6|0.3}} | node = {{val|22.9|0.2}} | periastron = {{val|fmt=none|2454983.0|0.2}} | periarg = {{val|293.0|0.6}} | k1 = {{val|23.42|0.05}} | k2 = {{val|32.0|0.4}} }} {{Starbox detail | age_gyr = 3.0<ref name=orbit/> | component1 = ο Dra A | mass = 1.35<ref name=orbit/> | radius = 25.1<ref name=orbit/> | luminosity = 220<ref name=orbit/> | temperature = {{val|4400|fmt=commas}}<ref name=aaa398_1163/> | gravity = 1.769<ref name=orbit/> | metal_fe = −0.5<ref name=perkins/> | rotation = 79<ref name=orbit/> | rotational_velocity = 20.0<ref name=BohmVitense2000/> | age = | component2 = ο Dra B | mass2 = 0.99<ref name=orbit/> | radius2 = 1.0<ref name=orbit/> | luminosity2 = 1.3<ref name=orbit/> | temperature2 = {{val|6000|fmt=commas}}<ref name=orbit/> | gravity2 = 4.43<ref name=orbit/> | metal_fe2 = | rotation2 = | rotational_velocity2 = }} {{Starbox catalog | names = [[Bayer designation|Omicron]] Draconis, [[Flamsteed designation|47]] Draconis, [[Bright Star Catalogue|HR]] 7125, [[Henry Draper Catalogue|HD]] 175306, [[Hipparcos catalogue|HIP]] 92512, [[Durchmusterung|BD]]+59°1925 }} {{Starbox reference |Simbad = Omicron+Draconis }} {{Starbox end}}
'''Omicron Draconis''' (Latinised as '''ο Draconis''', abbreviated to ο Dra) is a [[giant star]] in the [[constellation]] [[Draco (constellation)|Draco]] located 322.93 [[light year]]s from the Earth. Its path in the night sky is [[circumpolar star|circumpolar]] for latitudes greater than 31<sup>o</sup> north, meaning the star never rises or sets when viewed in the night sky.
[[File:OmicronDraLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for Omicron Draconis, adapted from Roettenbacher ''et al.'' (2015)<ref name=orbit/>]]
This is a single-lined [[spectroscopic binary]] system,<ref name=aaa398_1163/> but the secondary has been detected using [[interferometry]]. It is an [[RS Canum Venaticorum variable]] system with eclipses. The total amplitude of variation is only a few hundredths of a magnitude.<ref name="orbit"/><ref name="IVSI"/> The secondary star is similar to the Sun, presumably a [[main-sequence]] star, while the primary is a [[giant star]] 25 times larger than the Sun and two hundred times more luminous.
== Identities as pole star == Omicron Draconis can be considered the north [[pole star]] of [[Mercury (planet)|Mercury]], as it is the closest star to Mercury's north [[celestial pole]].<ref>{{Cite journal|last=Sharrah|first=Paul C.|year=1975|title=Pole Stars of Other Planets|url=https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=2873&context=jaas|format=pdf|journal=Arkansas Academy of Sciences Proceedings|volume=XXIX|pages=62–63}}</ref> In addition to that, this star is currently the [[Moon]]'s north [[pole star]], which occurs once every 18.6 years.<ref>{{cite book |last=Moore |first=Patrick |author-link=Patrick Moore |title=The Guinness Book of Astronomy Facts & Feats |year=1983 |page=29 |quote=In 1968 the north pole star of the Moon was Omega Draconis; by 1977 it was 36 Draconis. The south pole star is Delta Doradus.}}</ref>
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==References== <references> <ref name="aaa398_1163">{{cite journal |last1=Pourbaix |first1=D. |last2=Boffin |first2=H. M. J. |date=February 2003 |title=Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component |journal=Astronomy and Astrophysics |volume=398 |issue=3 |pages=1163–1177 |arxiv=astro-ph/0211483 |bibcode=2003A&A...398.1163P |doi=10.1051/0004-6361:20021736 |s2cid=12361870}}</ref>
<ref name="BohmVitense2000">{{cite journal |last1=Böhm-Vitense |first1=Erika |last2=Carpenter |first2=Kenneth G. |last3=Robinson |first3=Richard D. |date=December 2000 |title=Ultraviolet Emission Lines in BA and Non-BA Giants |journal=The Astrophysical Journal |volume=545 |issue=2 |pages=992–999 |bibcode=2000ApJ...545..992B |doi=10.1086/317850 |doi-access=free}}</ref>
<ref name="IVSI">{{cite web |title=omi Dra |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=13951 |access-date=15 July 2022 |website=The International Variable Star Index |publisher=AAVSO}}</ref> </references>
{{Stars of Draco}}
[[Category:Bayer objects|Draconis, Omicron]] [[Category:Draco (constellation)]] [[Category:G-type giants]] [[Category:RS Canum Venaticorum variables]] [[Category:Eclipsing binaries]] [[Category:Flamsteed objects|Draconis, 47]] [[Category:Hipparcos objects|092512]] [[Category:Bright Star Catalogue objects|7125]] [[Category:Henry Draper Catalogue objects|175306]] [[Category:Durchmusterung objects]]