# Eta Draconis

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Star in the constellation Draco

η Draconis Location of η Draconis (circled) Observation data Epoch J2000.0 Equinox J2000.0 Constellation Draco Right ascension 16h 23m 59.48594s[1] Declination +61° 30′ 51.1699″[1] Apparent magnitude (V) +2.73[2] Characteristics Spectral type G8 III[2] U−B color index +0.70[3] B−V color index +0.91[3] Astrometry Radial velocity (Rv) −14.3[4] km/s Proper motion (μ) RA: −17.02[1] mas/yr Dec.: +56.95[1] mas/yr Parallax (π) 35.42±0.09 mas[1] Distance 92.1 ± 0.2 ly (28.23 ± 0.07 pc) Absolute magnitude (MV) +0.58[5] Details A Mass 2.55±0.26[6] M☉ Radius 10.46[7]–10.53[8] R☉ Luminosity 65.6±6.3[8] L☉ Surface gravity (log g) 2.82±0.11[6] cgs Temperature 5,018[7] K Metallicity [Fe/H] −0.088[7] dex Rotational velocity (v sin i) 8[9] km/s Age 650±100[8] Myr B Mass 0.672[10] M☉ Radius 0.577[10] R☉ Luminosity 0.206[10] L☉ Temperature 5,114[10] K Other designations Aldibain, Athebyne, 14 Draconis, BD+61 1591, FK5 822, HD 148387, HIP 80331, HR 6132, NSV 7713, SAO 17074, WDS 16240+6131.[11] Database references SIMBAD data

**Eta Draconis** (**η Draconis**, abbreviated **Eta Dra**, **η Dra**) is a [binary star](/source/Binary_star) in the northern [circumpolar constellation](/source/Circumpolar_constellation) of [Draco](/source/Draco_(constellation)). Despite having an [apparent visual magnitude](/source/Apparent_magnitude) of only +2.73,[2] it is the [second-brightest star](/source/List_of_stars_in_Draco) in this generally faint constellation. Based upon [parallax](/source/Parallax) measurements collected during the [Hipparcos](/source/Hipparcos) mission, this star is located at a distance of about 92.1 [light-years](/source/Light-year) (28.2 [parsecs](/source/Parsec)) from the [Sun](/source/Sun).[1]

The two components are designated **Eta Draconis A** (also named **Athebyne** [/ˈæθɪbaɪn/](https://en.wikipedia.org/wiki/Help:IPA/English)[12]) and **B**.

## Nomenclature

*η Draconis* ([Latinised](/source/Latinisation_of_names) to *Eta Draconis*) is the system's [Bayer designation](/source/Bayer_designation). The designations of the two components as *Eta Draconis A* and *B* derives from the convention used by the Washington Multiplicity Catalog (WMC) for [multiple star systems](/source/Star_system), and adopted by the [International Astronomical Union](/source/International_Astronomical_Union) (IAU).[13]

Eta Draconis, together with [Zeta Draconis](/source/Zeta_Draconis), bore the traditional [Arabic](/source/Arabic) name الذئبين *al-dhiʼbayn*, "the (two) wolves", lying in wait for the camel's foal, the little star [Al Rubaʽ](/source/Alruba), protected by the [Mother Camels](/source/Mother_Camels).[14]

In 2016, the IAU organized a [Working Group on Star Names](/source/IAU_Working_Group_on_Star_Names) (WGSN)[15] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire [multiple systems](/source/Multiple_star).[16] It approved the name *Athebyne* (a rendering of *adh-dhiʼbayn*) for the component Eta Draconis A on 5 September 2017. It approved the name *Aldhibah* (the female wolf) for Zeta Draconis A on the same date. Both are now so included in the List of IAU-approved Star Names.[12]

In [Chinese](/source/Chinese_astronomy), 紫微左垣 (*Zǐ Wēi Zuǒ Yuán*), meaning *[Left Wall of Purple Forbidden Enclosure](/source/Purple_Forbidden_enclosure)*, refers to an [asterism](/source/Asterism_(astronomy)) consisting of Eta Draconis, [Iota Draconis](/source/Iota_Draconis), [Theta Draconis](/source/Theta_Draconis), Zeta Draconis, [Upsilon Draconis](/source/Upsilon_Draconis), [73 Draconis](https://en.wikipedia.org/w/index.php?title=73_Draconis&action=edit&redlink=1), [Gamma Cephei](/source/Gamma_Cephei) and [23 Cassiopeiae](/source/23_Cassiopeiae).[17] Consequently, the [Chinese name](/source/Chinese_star_names) for Eta Draconis itself is 紫微左垣三 (*Zǐ Wēi Zuǒ Yuán sān*, English: the Third Star of Left Wall of Purple Forbidden Enclosure),[18] representing 少宰 (*Shàozǎi*), meaning *The Second Premier*.[19] Possibly, 少宰 (Shàozǎi) is westernized into *Hea Tsae* by R.H. Allen with meaning "the Lowest Steward" but it was for Theta Draconis.[20]

## Properties

Eta Draconis A is a star with 2.88[7] times the [mass of the Sun](/source/Solar_mass). The [spectrum](/source/Stellar_spectrum) matches a [stellar classification](/source/Stellar_classification) of G8 III,[2] with the [luminosity class](/source/Stellar_classification#Yerkes_spectral_classification) III indicating this is an [evolved](/source/Stellar_evolution) [giant star](/source/Giant_star) that has exhausted the supply of hydrogen at its core. It reached this stage in only 650[8] million years because higher mass stars such as this consume the supply of hydrogen more rapidly than the Sun. The [radius](/source/Radius) of Eta Draconis, as determined by its [angular diameter](/source/Angular_diameter) and distance from Earth, is about 10.5 times the [radius of the Sun](/source/Solar_radius).[7][8] From its extended [envelope](/source/Stellar_atmosphere), it is radiating around 65[8] times the [luminosity of the Sun](/source/Solar_luminosity) at an [effective temperature](/source/Effective_temperature) of 5,018 K,[7] giving it the yellow glow of a G-type star.[21]

Eta Draconis B is located at an [angular separation](/source/Angular_distance) of 5.1 [arcseconds](/source/Minute_and_second_of_arc) from the primary. This is an 8.8 magnitude [K-type](/source/Stellar_classification#Class_K) [main sequence](/source/Main_sequence) star with a stellar classification of K2 V.[22] At the estimated distance of this star system, the two stars are separated by a physical distance of at least 140 [AU](/source/Astronomical_unit) and require at least a millennium to complete an [orbit](/source/Orbit).[23]

## References

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1. ^ [***a***](#cite_ref-Hardegree-Ullman_10-0) [***b***](#cite_ref-Hardegree-Ullman_10-1) [***c***](#cite_ref-Hardegree-Ullman_10-2) [***d***](#cite_ref-Hardegree-Ullman_10-3) Hardegree-Ullman, Kevin K.; Apai, Dániel; Bergsten, Galen J.; Pascucci, Ilaria; López-Morales, Mercedes (2023-06-01). ["Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets"](https://doi.org/10.3847%2F1538-3881%2Facd1ec). *The Astronomical Journal*. **165** (6): 267. [arXiv](/source/ArXiv_(identifier)):[2304.12490](https://arxiv.org/abs/2304.12490). [Bibcode](/source/Bibcode_(identifier)):[2023AJ....165..267H](https://ui.adsabs.harvard.edu/abs/2023AJ....165..267H). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/acd1ec](https://doi.org/10.3847%2F1538-3881%2Facd1ec). [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256).

1. **[^](#cite_ref-SIMBAD_11-0)** ["eta Dra"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eta+Dra). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2012-02-20.

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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 [Eta Draconis](https://en.wikipedia.org/wiki/Eta_Draconis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Eta_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.