# 50 Draconis

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Binary star system in the constellation Draco

50 Draconis Observation data Epoch J2000 Equinox J2000 Constellation Draco[1] Right ascension 18h 46m 22.24188s[2] Declination +75° 26′ 02.2400″[2] Apparent magnitude (V) 5.369±0.001[3] (5.997 + 6.238)[4] Characteristics Evolutionary stage Main sequence[4] Spectral type A2Vp[1] Variable type Rotating ellipsoidal variable[4] Astrometry Radial velocity (Rv) −6.53±0.09[4] km/s Proper motion (μ) RA: −17.061 mas/yr[2] Dec.: +70.391 mas/yr[2] Parallax (π) 11.4150±0.1058 mas[2] Distance 286 ± 3 ly (87.6 ± 0.8 pc) Absolute magnitude (MV) +0.70[1] Orbit[4] Period (P) 4.117719(2) days Semi-major axis (a) 13.184±0.026 R☉ Eccentricity (e) 0.0021±0.0003 Inclination (i) 49.9±0.8° Argument of periastron (ω) (secondary) 94.85±0.02° Semi-amplitude (K1) (primary) 78.93±0.02 km/s Semi-amplitude (K2) (secondary) 82.96±0.20 km/s Details[4] 50 Dra A Mass 2.08±0.08 M☉ Radius 2.06±0.09 R☉ Surface gravity (log g) 4.13±0.05 cgs Temperature 9,800±100 K Metallicity [Fe/H] +0.21±0.09 dex Rotation 4.117719(2) days Rotational velocity (v sin i) 19±1 km/s 50 Dra B Mass 1.97±0.08 M☉ Radius 1.99±0.09 R☉ Surface gravity (log g) 4.13±0.05 cgs Temperature 9,200±200 K Metallicity [Fe/H] +0.08±0.10 dex Rotation 4.117719(2) days Rotational velocity (v sin i) 19±1 km/s Other designations BD+75°682, HD 175286, HIP 92112, HR 7124, TYC 4583-2839-1[5] Database references SIMBAD data

**50 Draconis** is a [binary star](/source/Binary_star) in the constellation [Draco](/source/Draco_(constellation)). At an [apparent magnitude](/source/Apparent_magnitude) of +5.369, it is faintly visible to the [naked eye](/source/Naked_eye) in locations far from [light pollution](/source/Light_pollution). [Parallax](/source/Parallax) measurements give a distance of 286 [light-years](/source/Light-year) (88 [parsecs](/source/Parsec)).

## Characteristics

50 Draconis was first discovered to be a binary in 1914 at the [American Astronomical Society](/source/American_Astronomical_Society).[6] A [spectroscopic binary](/source/Spectroscopic_binary), the existence of a companion was inferred from periodic variations in the [spectral lines](/source/Spectral_line), corresponding to the orbital motion of the stars.[4]

The system has a very tight orbit, with an orbital period of just 4.11 days and an orbital separation of 13.184 solar radii (9,172,000 km) at a low [eccentricity](/source/Orbital_eccentricity) of 0.002. The orbit is inclined at 50 degrees from Earth and thus the system is not [eclipsing](/source/Eclipsing_binary). 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](/source/Rotating_ellipsoidal_variable). The stars are [tidally locked](/source/Tidally_locked), with rotation periods synchronized with the orbital period.[4]

Relative to the Sun, the stars are overabundant in [iron peak](/source/Iron_peak) and [rare-earth elements](/source/Rare-earth_element), but underabundant in [scandium](/source/Scandium), classifying them as [Am stars](/source/Am_star). The components are similar to each other, with around twice the mass and radius of the Sun, and [effective temperatures](/source/Effective_temperature) of 9,800 and 9,200 [K](/source/Kelvin) for the primary and secondary respectively, temperatures at the upper range for Am stars.[4]

## References

1. ^ [***a***](#cite_ref-XHIP_1-0) [***b***](#cite_ref-XHIP_1-1) [***c***](#cite_ref-XHIP_1-2) Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *[Astronomy Letters](/source/Astronomy_Letters)*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [XHIP record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-ref=VIZ681510a8389ecb&-out.src=V%2F137D%2FXHIP&-nav=cat%3AV%2F137D%26tab%3A{V%2F137D%2FXHIP}%26key%3Asource%3DV%2F137D%2FXHIP%26HTTPPRM%3A&-source=V%2F137D%2FXHIP&-out=HIP&HIP=92112&-out=Comp&-out=Gr&-out=RAJ2000&-out=DEJ2000&-out=Dist&-out=X&-out=Y&-out=Z&-out=SpType&-out=Simbad&-out=Hpmag&-out=Lum&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-DR3_2-0) [***b***](#cite_ref-DR3_2-1) [***c***](#cite_ref-DR3_2-2) [***d***](#cite_ref-DR3_2-3) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D2268467486545969792%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. **[^](#cite_ref-Paunzen2015_3-0)** Paunzen, E. (2015-08-01). "A new catalogue of Strömgren-Crawford uvbyβ photometry". *Astronomy and Astrophysics*. **580**: A23. [arXiv](/source/ArXiv_(identifier)):[1506.04568](https://arxiv.org/abs/1506.04568). [Bibcode](/source/Bibcode_(identifier)):[2015A&A...580A..23P](https://ui.adsabs.harvard.edu/abs/2015A&A...580A..23P). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201526413](https://doi.org/10.1051%2F0004-6361%2F201526413). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. ^ [***a***](#cite_ref-Skarka2025_4-0) [***b***](#cite_ref-Skarka2025_4-1) [***c***](#cite_ref-Skarka2025_4-2) [***d***](#cite_ref-Skarka2025_4-3) [***e***](#cite_ref-Skarka2025_4-4) [***f***](#cite_ref-Skarka2025_4-5) [***g***](#cite_ref-Skarka2025_4-6) [***h***](#cite_ref-Skarka2025_4-7) [***i***](#cite_ref-Skarka2025_4-8) Skarka, M.; Lipták, J.; Niemczura, E.; Mikulášek, Z.; Cabezas, M.; Vítková, M.; Karjalainen, R.; Kabáth, P. (June 2025). "50 Dra: Am-type twins with additional variability in a non-eclipsing system". *Astronomy & Astrophysics*. **698**: A48. [arXiv](/source/ArXiv_(identifier)):[2504.05854](https://arxiv.org/abs/2504.05854). [Bibcode](/source/Bibcode_(identifier)):[2025A&A...698A..48S](https://ui.adsabs.harvard.edu/abs/2025A&A...698A..48S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202452341](https://doi.org/10.1051%2F0004-6361%2F202452341). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. **[^](#cite_ref-SIMBAD_5-0)** ["50 Dra"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=50+Dra). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg).

1. **[^](#cite_ref-Harper1915_6-0)** Harper, W. E. (April 1915). "The Orbits of the Spectroscopic Components of 50 Draconis". *Journal of the Royal Astronomical Society of Canada*. **9**: 165. [Bibcode](/source/Bibcode_(identifier)):[1915JRASC...9..165H](https://ui.adsabs.harvard.edu/abs/1915JRASC...9..165H). [ISSN](/source/ISSN_(identifier)) [0035-872X](https://search.worldcat.org/issn/0035-872X).

v t e Constellation of Draco List of stars in Draco Draco in Chinese astronomy Stars Bayer α (Thuban) β (Rastaban) γ (Eltanin) δ (Altais) ε (Tyl) ζ (Aldhibah) η (Athebyne) θ ι (Edasich) κ λ (Giausar) μ (Alrakis) ν (Kuma) ξ (Grumium) ο π ρ σ (Alsafi) τ υ φ χ ψ1 (Dziban) ψ2 ω Flamsteed 4 6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 50 59 64 (e) 68 Variable TW YY AG BY CL CM CX DO EK HP V581 HR 3751 4126 4934 5811 6237 6518 6618 (Alruba) 6817 7137 7783 HD 109246 (Funi) 101364 128717 147379 156279 158259 176693 191939 Other 2MASS 1237+6526 2MASS J17554042+6551277 G 240-72 GD 356 Gliese 420 Gliese 625 Gliese 687 GRW +70 8247 Kepler-4 Kepler-10 Kepler-12 Kepler-90 Kepler-296 KOI-256 LP 71-82 Qatar-1 SDSS J1240+6710 Struve 2398 TOI-1136 WD 1856+534 WISE 1647+5632 WISE 1841+7000 Exoplanets HD 139357 b HD 167042 b ι Dra b (Hypatia) Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i Kepler-296b c d e f TOI-1452 b TrES-2b Star clusters LAMOST 1 Nebulae Cat's Eye Nebula NGC 6742 Galaxies NGC 3147 3197 3735 4121 4125 4221 4236 4319 4331 4332 4363 4441 4513 4545 4589 5678 5777 5866 5866B 5879 5905 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6338 6340 6365 6373 6394 6412 6503 6505 6566 6621 6622 6670 6676 6786 6789 Other 1ES 1927+654 1ES 1959+650 3C 249.1 3C 305 3C 319 3C 343 3C 343.1 3C 351 3C 356 3C 371 3C 380 3C 390.3 3C 401 4C +72.26 4C 73.08 8C 1241+735 Abell 2218 BCG Bean galaxy Beaver galaxy BZQ J1727+5510 Draco Dwarf Draco II GB 1508+5714 Goldfish galaxy H1821+643 HFLS3 IERS B1946+708 IRAS F17179+5444 IRAS 18580+6527 J120011.1+680924.8 KKR 25 Markarian 817 Markarian 876 Original TRG PGC 39058 Porphyrion QSO B1823+568 RGZ J172749.5+534647 S5 1803+784 S5 2007+777 SDSS J1715+6008 Tadpole Galaxy UGC 9391 UGC 9405 UGC 11241 UGC 11411 WISEA J145223.62+611707.5 WN B1851+5707 Galaxy clusters Abell 2218 CL1358+62 Draco Supercluster NGC 5866 Group Astronomical events SN 2003jb SN 2005B SN 2016aps Swift J1644+57 Category

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Adapted from the Wikipedia article [50 Draconis](https://en.wikipedia.org/wiki/50_Draconis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/50_Draconis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.