{{Short description|Wide binary star system in the constellation of Draco}} {{about-distinguish|b Draconis|beta Draconis{{!}}β (beta) Draconis}} {{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=39 Draconis |x=180|y=775 }} | caption = Location of 39 Draconis (circled in red) }} {{Starbox observe 2s |epoch=[[J2000]] |constell=[[Draco (constellation)|Draco]]<ref name=xhip>{{cite XHIP|90156}}</ref> |component1=A |ra1={{RA|18|23|54.60689}}<ref name=dr3a/> |dec1={{DEC|+58|48|02.6667}}<ref name=dr3a/> |appmag_v1=5.06<ref name=ORB6/> |component2=B |ra2={{RA|18|23|54.51639}}<ref name=dr3b/> |dec2={{DEC|+58|48|06.3674}}<ref name=dr3b/> |appmag_v2=8.07<ref name=ORB6/> }} {{Starbox character |type=[[main sequence]]<ref name=dr3a/><ref name=zorec2012>{{cite journal |last1=Zorec |first1=J. |last2=Royer |first2=F. |title=Rotational velocities of A-type stars. IV. Evolution of rotational velocities |journal=Astronomy and Astrophysics |date=2012 |volume=537 |pages=A120 |doi=10.1051/0004-6361/201117691 |arxiv=1201.2052 |bibcode=2012A&A...537A.120Z }}</ref> |class=A1V + F5V<ref name=Lutz>{{cite journal|bibcode=1977AJ.....82..431L|doi=10.1086/112066|title=Spectral classification and UBV photometry of bright visual double stars|journal=The Astronomical Journal|volume=82|pages=431|year=1977|last1=Lutz|first1=T. E.|last2=Lutz|first2=J. H.|author2-link= Julie Lutz|doi-access=free}}</ref> |b-v=+0.10<ref name=EgUBV>{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|date=1986|bibcode= 1986EgUBV........0M}}</ref> |u-b=+0.06<ref name=EgUBV/> |variable= }} {{Starbox astrometry |radial_v={{Val|−24.53|0.23}}<ref name=SB9>{{cite journal|title=S<sub>B<sup>9</sup></sub>: The ninth catalogue of spectroscopic binary orbits|display-authors=1|author1=Pourbaix, D.|author2=Tokovinin, A. A.|author3=Batten, A. H.|author4=Fekel, F. C.|author5=Hartkopf, W. I.|author6=Levato, H.|author7=Morrell, N. I.|author8=Torres, G.|author9=Udry, S.|journal=Astronomy and Astrophysics|volume=424|issue=2|pages=727–732|year=2004|doi=10.1051/0004-6361:20041213|arxiv=astro-ph/0406573|bibcode=2004A&A...424..727P|s2cid=119387088}}</ref> }}{{Starbox astrometry|no_heading=y |component1=A |prop_mo_ra=−37.322<ref name=dr3a/> |prop_mo_dec=+62.892<ref name=dr3a/> |parallax=17.1615 |p_error=0.0631 |parallax_footnote=<ref name=dr3a>{{cite Gaia DR3|2157548616097840000}}</ref> |absmag_v=+1.31<ref name=Novakovic/> |component2=B |prop_mo_ra2=−41.742<ref name=dr3b/> |prop_mo_dec2=+61.076<ref name=dr3b/> |parallax2=17.2293 |p_error2=0.0219 |parallax_footnote2=<ref name=dr3b>{{cite Gaia DR3|2157548616097840128}}</ref> |absmag_v2=+4.32<ref name=Novakovic/> }} {{Starbox orbit |reference=<ref name=ORB6>{{cite web|url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|title=Sixth Catalog of Orbits of Visual Binary Stars|work=United States Naval Observatory|access-date=2017-06-22|archive-date=2017-08-01|archive-url=https://web.archive.org/web/20170801102553/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|url-status=dead}}</ref> |period={{val|fmt=commas|4,000|200}} |axis={{val|6.6|0.3}} |inclination={{val|107.7| 0.12}} |node={{val|179.9|0.10}} |periastron={{val|fmt=none|5671.40|12.08}} |eccentricity={{val|0.553|0.005}} |periarg={{val|128.0|2.2}} }} {{Starbox detail |component1=39 Dra A |mass=2.12<ref name=Novakovic>{{cite journal|bibcode=2006SerAJ.172...21N|doi=10.2298/SAJ0672021N|title=Orbits of four double stars|journal=Serbian Astronomical Journal|volume=172|issue=172|pages=21|year=2006|last1=Novakovic|first1=B.|last2=Todorovic|first2=N.|doi-access=free|s2cid=55352155 }}</ref> |luminosity=27<ref name=tic/> |temperature=8,630<ref name=tic/> |radius=2.3<ref name=tic/> |gravity=4.04<ref name=tic/> |rotational_velocity=186<ref name=zorec2012/> |age_myr=350<ref name=derosa2014>{{cite journal |last1=De Rosa |first1=R. J. |last2=Patience |first2=J. |last3=Wilson |first3=P. A. |last4=Schneider |first4=A. |last5=Wiktorowicz |first5=S. J. |last6=Vigan |first6=A. |last7=Marois |first7=C. |last8=Song |first8=I. |last9=MacIntosh |first9=B. |last10=Graham |first10=J. R. |last11=Doyon |first11=R. |last12=Bessell |first12=M. S. |last13=Thomas |first13=S. |last14=Lai |first14=O. |title=The VAST Survey - III. The multiplicity of A-type stars within 75 pc |journal=Monthly Notices of the Royal Astronomical Society |date=2014 |volume=437 |issue=2 |page=1216 |doi=10.1093/mnras/stt1932 |doi-access=free |arxiv=1311.7141 |bibcode=2014MNRAS.437.1216D }}</ref> |component2=39 Dra B |mass2=1.18<ref name=Novakovic/> |temperature2=6,271<ref name=tic>{{cite journal |last1=Stassun |first1=Keivan G. |last2=Oelkers |first2=Ryan J. |last3=Paegert |first3=Martin |last4=Torres |first4=Guillermo |last5=Pepper |first5=Joshua |last6=De Lee |first6=Nathan |last7=Collins |first7=Kevin |last8=Latham |first8=David W. |last9=Muirhead |first9=Philip S. |last10=Chittidi |first10=Jay |last11=Rojas-Ayala |first11=Bárbara |last12=Fleming |first12=Scott W. |last13=Rose |first13=Mark E. |last14=Tenenbaum |first14=Peter |last15=Ting |first15=Eric B. |last16=Kane |first16=Stephen R. |last17=Barclay |first17=Thomas |last18=Bean |first18=Jacob L. |last19=Brassuer |first19=C. E. |last20=Charbonneau |first20=David |last21=Ge |first21=Jian |last22=Lissauer |first22=Jack J. |last23=Mann |first23=Andrew W. |last24=McLean |first24=Brian |last25=Mullally |first25=Susan |last26=Narita |first26=Norio |last27=Plavchan |first27=Peter |last28=Ricker |first28=George R. |last29=Sasselov |first29=Dimitar |last30=Seager |first30=S. |display-authors=1 |title=The Revised TESS Input Catalog and Candidate Target List |journal=The Astronomical Journal |date=2019 |volume=158 |issue=4 |page=138 |doi=10.3847/1538-3881/ab3467 |doi-access=free |arxiv=1905.10694 |bibcode=2019AJ....158..138S }}</ref> |luminosity2=1.85<ref name=tic/> |radius2=1.15<ref name=tic/> |gravity2=4.40<ref name=tic/> |rotation2=5.9 days<ref name=lin2024>{{cite journal |last1=Lin |first1=Chia-Lung |last2=Apai |first2=Dániel |last3=Giampapa |first3=Mark S. |last4=Ip |first4=Wing-Huen |title=Scalable, Advanced Machine Learning Based Approaches for Stellar Flare Identification: Application to TESS Short-cadence Data and Analysis of a New Flare Catalog |journal=The Astronomical Journal |date=2024 |volume=168 |issue=6 |page=234 |doi=10.3847/1538-3881/ad7956 |doi-access=free |arxiv=2409.02540 |bibcode=2024AJ....168..234L }}</ref> |age_gyr2=2.6<ref name=ware2022>{{cite journal |last1=Ware |first1=Austin |last2=Young |first2=Patrick |last3=Truitt |first3=Amanda |last4=Spacek |first4=Alexander |title=Continuous Habitable Zones: Using Bayesian Methods to Prioritize Characterization of Potentially Habitable Worlds |journal=The Astrophysical Journal |date=2022 |volume=929 |issue=2 |page=143 |doi=10.3847/1538-4357/ac5c4e |doi-access=free |arxiv=2203.06259 |bibcode=2022ApJ...929..143W }}</ref> }} {{Starbox catalog |names={{odlist | B=b Dra | F=39 Dra | BD=+58°1809 | HD=170073 | HIP=90156 | HR=6923 | SAO=30949 }}<ref name=SIMBAD>{{cite simbad|title=* b Dra|access-date=21 June 2017}}</ref> }} {{Starbox reference |Simbad=39+Dra|sn=39 Dra |Simbad2=*+b+Dra+A|sn2=39 Dra A |Simbad3=*+b+Dra+B|sn3=39 Dra B }} {{Starbox end}} '''39 Draconis''' is a wide [[binary star]] system in the northern [[circumpolar constellation]] of [[Draco (constellation)|Draco]]. It has the [[Bayer designation]] '''b Draconis''', while ''39 Draconis'' is the [[Flamsteed designation]]. This system is visible to the naked eye as a dim, white-hued point of light with a combined [[apparent visual magnitude]] of 5.0.<ref name=xhip/> [[Stellar parallax|Parallax measurements]] made by the [[Gaia spacecraft]] put it at a distance of 190 light-years, or 58 parsecs away from the Sun. The system is moving closer to the Earth with a heliocentric [[radial velocity]] of −24.5&nbsp;km/s.<ref name=SB9/>

The two components of 39 Draconis have an [[angular separation]] of {{Val|6.621|ul=arcsecond}} and take almost 4,000 years to orbit each other.<ref name=ORB6/> The primary star is an early [[A-type main-sequence star]], having 2.12 times the [[mass of the Sun]] with a visual magnitude of 5.06.<ref name=ORB6/> The secondary is a magnitude 8.07<ref name=ORB6/> [[F-type main-sequence star]], and has 1.18 times the mass of the Sun.<ref name=Novakovic/>

The 8th-magnitude star HD 238865 is listed in double star catalogues as component C.<ref name=wds>{{cite journal | display-authors=1 | last1=Mason | first1=B. D. | last2=Wycoff | first2=G. L. | last3=Hartkopf | first3=W. I. | last4=Douglass | first4=G. G. | last5=Worley | first5=C. E. | title=The Washington Visual Double Star Catalog | year=2014 | volume=122 | journal=The Astronomical Journal | issue=6 | pages=3466–3471 | bibcode=2001AJ....122.3466M | doi=10.1086/323920 | doi-access=free }}</ref> It is separated from the other two stars by {{val|90|ul="}} and lies at about the same distance.<ref name=dr2c>{{cite DR2|2157548753536798208}}</ref> It is itself a [[spectroscopic binary]] with an F8 primary and a red dwarf secondary orbiting every 2.7 days.<ref name=derosa>{{cite journal |bibcode=2014MNRAS.437.1216D |title=The VAST Survey - III. The multiplicity of A-type stars within 75 pc |journal=Monthly Notices of the Royal Astronomical Society |volume=437 |issue=2 |pages=1216 |last1=De Rosa |first1=R. J. |last2=Patience |first2=J. |last3=Wilson |first3=P. A. |last4=Schneider |first4=A. |last5=Wiktorowicz |first5=S. J. |last6=Vigan |first6=A. |last7=Marois |first7=C. |last8=Song |first8=I. |last9=MacIntosh |first9=B. |last10=Graham |first10=J. R. |last11=Doyon |first11=R. |last12=Bessell |first12=M. S. |last13=Thomas |first13=S. |last14=Lai |first14=O. |year=2014 |arxiv=1311.7141 |doi=10.1093/mnras/stt1932 |doi-access=free |s2cid=88503488 }}</ref><ref name=tokovinin>{{cite journal |bibcode=1995AstL...21..247T |title=Spectroscopic components in multiple systems: ADS 11336C |journal=Astronomy Letters |volume=21 |issue=2 |pages=247 |last1=Tokovinin |first1=A. A. |last2=Smekhov |first2=M. G. |year=1995 }}</ref>

==References== {{reflist}}

{{Stars of Draco}}

<!-- Properties --> [[Category:A-type main-sequence stars]] [[Category:F-type main-sequence stars]] [[Category:Binary stars]] <!-- Catalogues --> [[Category:Draco (constellation)]] [[Category:Flamsteed objects|Draconis, 39]] [[Category:Durchmusterung objects|BD+58 1809]] [[Category:Bayer objects|Draconis, b]] [[Category:Henry Draper Catalogue objects|170073]] [[Category:Hipparcos objects|090156]] [[Category:Bright Star Catalogue objects|6923]]