{{Short description|Binary star system in the constellation Draco}} {{Starbox begin}} <!--{{Starbox image | image= }}--> {{Starbox observe | epoch = J2000 | constell = [[Draco (constellation)|Draco]]<ref name=XHIP/> | ra = {{RA|18|46|22.24188}}<ref name=DR3/> | dec = {{DEC|+75|26|02.2400}}<ref name=DR3/> | appmag_v = {{Val|5.369|0.001}}<ref name=Paunzen2015/><br/>(5.997 + 6.238)<ref name=Skarka2025/> }} {{Starbox character | type = [[Main sequence]]<ref name=Skarka2025/> | class = A2Vp<ref name=XHIP/> | u-b = | b-v = | variable = [[Rotating ellipsoidal variable]]<ref name=Skarka2025/> }} {{Starbox astrometry | radial_v = {{Val|-6.53|0.09}}<ref name=Skarka2025/> | prop_mo_ra = {{Val|-17.061}} | prop_mo_dec = {{val|+70.391}} | pm_footnote = <ref name=DR3/> | parallax = 11.4150 | p_error = 0.1058 | parallax_footnote = <ref name=DR3/> | absmag_v = +0.70<ref name=XHIP/> }} {{Starbox orbit | reference = <ref name=Skarka2025/> | period_unitless = {{val|4.117719|(2)}} days | axis_unitless = {{Val|13.184|0.026|ul=solar radius}} | eccentricity = {{Val|0.0021|0.0003}} | inclination = {{Val|49.9|0.8}} | periarg = {{Val|94.85|0.02}} | k1 = {{Val|78.93|0.02}} | k2 = {{Val|82.96|0.20}} }} {{Starbox detail | source = <ref name=Skarka2025/> | component1 = 50 Dra A | mass = {{Val|2.08|0.08}} | radius = {{Val|2.06|0.09}} | luminosity = | temperature = {{Val|9800|100|fmt=commas}} | gravity = {{Val|4.13|0.05}} | rotation = {{val|4.117719|(2)}} days | rotational_velocity = {{Val|19|1}} | metal_fe = {{Val|+0.21|0.09}} | age_gyr = | component2 = 50 Dra B | mass2 = {{Val|1.97|0.08}} | radius2 = {{Val|1.99|0.09}} | luminosity2 = | temperature2 = {{Val|9200|200|fmt=commas}} | gravity2 = {{Val|4.13|0.05}} | metal2_fe = {{Val|+0.08|0.10}} | rotation2 = {{val|4.117719|(2)}} days | rotational_velocity2 = {{Val|19|1}} | age_gyr2 = }} {{Starbox catalog | names = {{odlist | HR=7124 |HD=175286 | HIP=92112 | BD=+75°682 | TYC=4583-2839-1 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=50+Dra }} {{Starbox end}} '''50 Draconis''' is a [[binary star]] in the constellation [[Draco (constellation)|Draco]]. At an [[apparent magnitude]] of +5.369, it is faintly visible to the [[naked eye]] in locations far from [[light pollution]]. [[Parallax]] measurements give a distance of {{convert|286|ly|pc|abbr=off|lk=on}}.
==Characteristics== 50 Draconis was first discovered to be a binary in 1914 at the [[American Astronomical Society]].<ref name=Harper1915/> A [[spectroscopic binary]], the existence of a companion was inferred from periodic variations in the [[spectral line]]s, corresponding to the orbital motion of the stars.<ref name=Skarka2025/>
The system has a very tight orbit, with an orbital period of just 4.11 days and an orbital separation of {{convert|13.184|solar radius|km}} at a low [[orbital eccentricity|eccentricity]] of 0.002. The orbit is inclined at 50 degrees from Earth and thus the system is not [[eclipsing binary|eclipsing]]. The components are so close to each other that their shapes are distorted by gravity, and during the orbit the surfaces visible from Earth, and hence the luminosities, vary, making the system a [[rotating ellipsoidal variable]]. The stars are [[tidally locked]], with rotation periods synchronized with the orbital period.<ref name=Skarka2025/>
Relative to the Sun, the stars are overabundant in [[iron peak]] and [[rare-earth element]]s, but underabundant in [[scandium]], classifying them as [[Am star]]s. The components are similar to each other, with around twice the mass and radius of the Sun, and [[effective temperature]]s of 9,800 and 9,200 [[Kelvin|K]] for the primary and secondary respectively, temperatures at the upper range for Am stars.<ref name=Skarka2025/>
==References== <references>
<ref name=DR3>{{cite DR3|2268467486545969792 }}</ref>
<ref name=XHIP>{{Cite XHIP|92112}}</ref>
<ref name=SIMBAD>{{Cite SIMBAD|title=50 Dra}}</ref>
<ref name=Paunzen2015>{{Cite journal |last=Paunzen |first=E. |date=2015-08-01 |title=A new catalogue of Strömgren-Crawford uvbyβ photometry |bibcode=2015A&A...580A..23P |journal=Astronomy and Astrophysics |volume=580 |pages=A23 |doi=10.1051/0004-6361/201526413 |issn=0004-6361|arxiv=1506.04568 }}</ref>
<ref name=Skarka2025>{{Cite journal |last1=Skarka |first1=M. |last2=Lipták |first2=J. |last3=Niemczura |first3=E. |last4=Mikulášek |first4=Z. |last5=Cabezas |first5=M. |last6=Vítková |first6=M. |last7=Karjalainen |first7=R. |last8=Kabáth |first8=P. |date=June 2025 |title=50 Dra: Am-type twins with additional variability in a non-eclipsing system |journal=Astronomy & Astrophysics |volume=698 |pages=A48 |doi=10.1051/0004-6361/202452341 |arxiv=2504.05854 |bibcode=2025A&A...698A..48S |issn=0004-6361}}</ref>
<ref name=Harper1915>{{Cite journal |last=Harper |first=W. E. |date=April 1915 |title=The Orbits of the Spectroscopic Components of 50 Draconis |journal=Journal of the Royal Astronomical Society of Canada |bibcode=1915JRASC...9..165H |language=en |volume=9 |pages=165 |issn=0035-872X}}</ref>
</references> {{Stars of Draco}} [[Category:A-type main-sequence stars]] [[Category:Am stars]] [[Category:Chemically peculiar stars]] [[Category:Draco (constellation)]] [[Category:Flamsteed objects|Draconis, 50]] [[Category:Hipparcos objects|92112]] [[Category:Bright Star Catalogue objects|7124]] [[Category:Henry Draper Catalogue objects|175286]] [[Category:Durchmusterung objects|BD+75 682]]