# 18 Draconis

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Star in the constellation Draco

18 Draconis Location of 18 Dra (circled in red) Observation data Epoch J2000 Equinox J2000 Constellation Draco Right ascension 16h 40m 55.11952s[1] Declination +64° 35′ 20.5824″[1] Apparent magnitude (V) 4.84[2] Characteristics Evolutionary stage horizontal branch[3] Spectral type K0 III CN−0.5 CH−2 Ca1[4] B−V color index 1.212±0.003[2] Astrometry Radial velocity (Rv) −1.37±0.09[5] km/s Proper motion (μ) RA: −0.599[1] mas/yr Dec.: −17.436[1] mas/yr Parallax (π) 4.5045±0.1730 mas[1] Distance 720 ± 30 ly (222 ± 9 pc) Absolute magnitude (MV) −1.92[2] Details[3] Mass 3.81±0.38 M☉ Radius 46.83±1.74 R☉ Luminosity 786.7±56.3 L☉ Surface gravity (log g) 1.69±0.06 cgs Temperature 4,471±23 K Metallicity [Fe/H] −0.13±0.10 dex Age 280±80 Myr Other designations g Dra, 18 Dra, BD+64°1145, FK5 3326, HD 151101, HIP 81660, HR 6223, SAO 17188[6] Database references SIMBAD data

18 Draconis in optical light

**18 Draconis** is a likely [binary star](/source/Binary_star)[7] system in the northern [circumpolar constellation](/source/Circumpolar_constellation) of [Draco](/source/Draco_(constellation)). With an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 4.84,[2] it is just bright enough to be faintly visible to the naked eye. The distance to this system, as estimated from an annual [parallax shift](/source/Stellar_parallax) of 4.5 [mas](/source/Milliarcsecond),[1] is roughly 720 [light years](/source/Light_year) (220 [parsecs](/source/Parsecs)). It is moving closer to the [Sun](/source/Sun) with a heliocentric [radial velocity](/source/Radial_velocity) of −1.4 km/s,[5] and is a probable member of the [Sirius](/source/Sirius) stream of co-moving stars.[8]

The visible component has a [stellar classification](/source/Stellar_classification) of K0 III CN−0.5 CH−2 Ca1,[4] indicating it is an [evolved](/source/Stellar_evolution) [K-type](/source/K-type_star) [giant star](/source/Giant_star) with some [abundance peculiarities](/source/Chemically_peculiar_star) in its [atmosphere](/source/Stellar_atmosphere). At the age of around 280 million years, it is most likely (99% chance) on the [horizontal branch](/source/Horizontal_branch).[3] It is a [barium star](/source/Barium_star), which suggests it may have a degenerate [white dwarf](/source/White_dwarf) companion from which it accreted materials during an earlier stage of its evolution.[9][7] 18 Dra has an estimated 3.8 times the [mass of the Sun](/source/Mass_of_the_Sun) and has expanded to 47 times the [Sun's radius](/source/Sun's_radius). The star is radiating 787 times the [Sun's luminosity](/source/Sun's_luminosity) from its enlarged [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 4,471 K.[3]

## References

1. ^ [***a***](#cite_ref-GaiaDR2_1-0) [***b***](#cite_ref-GaiaDR2_1-1) [***c***](#cite_ref-GaiaDR2_1-2) [***d***](#cite_ref-GaiaDR2_1-3) [***e***](#cite_ref-GaiaDR2_1-4) [***f***](#cite_ref-GaiaDR2_1-5) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051).

1. ^ [***a***](#cite_ref-Anderson2012_2-0) [***b***](#cite_ref-Anderson2012_2-1) [***c***](#cite_ref-Anderson2012_2-2) [***d***](#cite_ref-Anderson2012_2-3) Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *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), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-reffert2015_3-0) [***b***](#cite_ref-reffert2015_3-1) [***c***](#cite_ref-reffert2015_3-2) [***d***](#cite_ref-reffert2015_3-3) Reffert, Sabine; et al. (2015), "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity", *Astronomy & Astrophysics*, **574**: A116, [arXiv](/source/ArXiv_(identifier)):[1412.4634](https://arxiv.org/abs/1412.4634), [Bibcode](/source/Bibcode_(identifier)):[2015A&A...574A.116R](https://ui.adsabs.harvard.edu/abs/2015A&A...574A.116R), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201322360](https://doi.org/10.1051%2F0004-6361%2F201322360), [hdl](/source/Hdl_(identifier)):[10722/215277](https://hdl.handle.net/10722%2F215277), [S2CID](/source/S2CID_(identifier)) [59334290](https://api.semanticscholar.org/CorpusID:59334290).

1. ^ [***a***](#cite_ref-perkins1989_4-0) [***b***](#cite_ref-perkins1989_4-1) Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", *Astrophysical Journal Supplement Series*, **71**: 245, [Bibcode](/source/Bibcode_(identifier)):[1989ApJS...71..245K](https://ui.adsabs.harvard.edu/abs/1989ApJS...71..245K), [doi](/source/Doi_(identifier)):[10.1086/191373](https://doi.org/10.1086%2F191373), [S2CID](/source/S2CID_(identifier)) [123149047](https://api.semanticscholar.org/CorpusID:123149047).

1. ^ [***a***](#cite_ref-deBruijne2012_5-0) [***b***](#cite_ref-deBruijne2012_5-1) de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", *Astronomy & Astrophysics*, **546**: 14, [arXiv](/source/ArXiv_(identifier)):[1208.3048](https://arxiv.org/abs/1208.3048), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...546A..61D](https://ui.adsabs.harvard.edu/abs/2012A&A...546A..61D), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201219219](https://doi.org/10.1051%2F0004-6361%2F201219219), [S2CID](/source/S2CID_(identifier)) [59451347](https://api.semanticscholar.org/CorpusID:59451347), A61.

1. **[^](#cite_ref-SIMBAD_6-0)** ["g Dra"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=g+Dra). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2018-07-17.

1. ^ [***a***](#cite_ref-Eggleton2008_7-0) [***b***](#cite_ref-Eggleton2008_7-1) Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", *Monthly Notices of the Royal Astronomical Society*, **389** (2): 869, [arXiv](/source/ArXiv_(identifier)):[0806.2878](https://arxiv.org/abs/0806.2878), [Bibcode](/source/Bibcode_(identifier)):[2008MNRAS.389..869E](https://ui.adsabs.harvard.edu/abs/2008MNRAS.389..869E), [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2008.13596.x](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x), [S2CID](/source/S2CID_(identifier)) [14878976](https://api.semanticscholar.org/CorpusID:14878976).

1. **[^](#cite_ref-Famaey2005_8-0)** Famaey, B.; et al. (2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", *Astronomy and Astrophysics*, **430**: 165–186, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0409579](https://arxiv.org/abs/astro-ph/0409579), [Bibcode](/source/Bibcode_(identifier)):[2005A&A...430..165F](https://ui.adsabs.harvard.edu/abs/2005A&A...430..165F), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20041272](https://doi.org/10.1051%2F0004-6361%3A20041272), [S2CID](/source/S2CID_(identifier)) [17804304](https://api.semanticscholar.org/CorpusID:17804304).

1. **[^](#cite_ref-gomez_9-0)** Gomez, A. E.; et al. (1997), "Absolute magnitudes and kinematics of barium stars", *Astronomy and Astrophysics*, **319**: 881, [Bibcode](/source/Bibcode_(identifier)):[1997A&A...319..881G](https://ui.adsabs.harvard.edu/abs/1997A&A...319..881G).

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 [18 Draconis](https://en.wikipedia.org/wiki/18_Draconis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/18_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.