# EK Draconis

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Star in the constellation Draco

EK Draconis Location of EK Draconis Observation data Epoch J2000 Equinox J2000 Constellation Draco Right ascension 14h 39m 00.210s[1] Declination +64° 17′ 29.98″[1] Apparent magnitude (V) 7.53 – 7.64[2] Characteristics Evolutionary stage Main sequence[3] Spectral type G5V Fe-0.7 CH-1 (k)[4] Variable type BY Dra[2] Astrometry Radial velocity (Rv) −21.12±0.19[1] km/s Proper motion (μ) RA: −135.751[1] mas/yr Dec.: −37.089[1] mas/yr Parallax (π) 29.0661±0.0217 mas[1] Distance 112.21 ± 0.08 ly (34.40 ± 0.03 pc) Details Mass 1.0[3] M☉ Radius 0.99[5] R☉ Luminosity 0.83[3] L☉ Surface gravity (log g) 4.46±0.22[6] cgs Temperature 5,682±75[6] K Metallicity [Fe/H] [ M / H ] {\displaystyle {\begin{smallmatrix}\left[{\ce {M}}/{\ce {H}}\right]\end{smallmatrix}}} = −0.20±0.03[6] dex Rotation 2.69 days[7] Rotational velocity (v sin i) 16.0[7] km/s Age 700±180[6] Myr Other designations EK Dra, BD+64 1017, GJ 559.1, HD 129333, HIP 71631, SAO 16453, TIC 159613900, TYC 4176-540-1, 2MASS J14390026+6417299, SDSS J143900.24+641730.1[8] Database references SIMBAD data

**EK Draconis** (abbreviated **EK Dra**, also known as **HD 129333** or **HIP 71631**) is a young active [G-type main-sequence star](/source/G-type_main-sequence_star) in the Northern [constellation](/source/Constellation) of [Draco](/source/Draco_(constellation)). It is located approximately 112 [light-years](/source/Light-year) away from the [solar system](/source/Solar_System). With an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 7.6, it is too faint to be visible to the naked eye and requires [binoculars](/source/Binoculars) or a small [telescope](/source/Telescope) for observation.[9] EK Draconis is a [Solar analog](/source/Solar_analog), similar in spectral type and mass to the [Sun](/source/Sun) but significantly younger at 50–125 million years old.[10][11] The star is notable for its high levels of magnetic activity, including powerful [superflares](/source/Superflare) and [coronal mass ejections](/source/Coronal_mass_ejection) (CMEs), which provide insights into the behavior of the young Sun and its potential impacts on early planetary systems.[12][13] EK Draconis is classified as a [BY Draconis variable](/source/BY_Draconis_variable), exhibiting brightness variations due to large starspots and rapid rotation.

## Characteristics

EK Draconis is a yellow dwarf [star](/source/Star) with a spectral classification of G5V. Its effective temperature is approximately 5,561 K, close to that of our Sun. Estimates of its mass range from 0.95 to 1.1 solar masses, with a radius of about 0.94 to 1.2 [solar radii.](/source/Solar_radius) The star's [luminosity](/source/Luminosity) is roughly 0.97 times that of the Sun. Its metallicity, measured by iron abundance, is slightly higher than solar at [Fe/H] = 0.07. The star's [surface gravity](/source/Surface_gravity) is approximately 4.47.[14]

The star lies at a [galactic latitude](/source/Galactic_coordinate_system) of about 49° and a galactic longitude of 106°, placing it within the [Milky Way](/source/Milky_Way) disk. Its proper motion is −12.59 milliarcseconds per year in declination and −139.54 milliarcseconds per year in right ascension, with a radial velocity of −20.3 km/s, indicating it is approaching the Solar System.[9]

## Companion

EK Draconis is a single-lined [spectroscopic](/source/Spectroscopy) binary system, orbited by a low-mass companion. The companion is likely an M-dwarf star, with the system's orbital parameters determined through radial velocity measurements and [speckle interferometry](/source/Speckle_imaging). The [eccentricity](/source/Orbital_eccentricity) of the orbit is approximately 0.13, and the semi-major axis is large, suggesting a wide separation. Detailed orbital elements have been refined using data from multiple surveys, confirming EK Draconis as one of the nearest young binary systems evolving similarly to the Sun.[15]

## Observation & Stellar activity

EK Draconis [light curve](/source/Light_curve) plotted from *[TESS](/source/Transiting_Exoplanet_Survey_Satellite)* data[16]

EK Draconis rotates rapidly for a G-type star, with an equatorial rotation period of about 2.5–2.8 days and a projected rotational velocity of 16.4 km/s. The star exhibits significant differential rotation, with shear rates varying between 0.19 and 0.38 rad/d across observational epochs, leading to laptimes (the time for the equator to lap the poles) of 16–48 days. Its inclination angle is approximately 60°.[14][9]

The star's [magnetic field](/source/Magnetic_field) is strong and dynamic, with average strengths ranging from 58 to 92 G over multi-year observations. It features a predominantly toroidal and axisymmetric field, with poloidal components that are often non-axisymmetric. No polarity reversals have been detected, but the field evolves over months, transitioning between toroidal-dominant and balanced poloidal-toroidal configurations. Surface features include large starspots at intermediate latitudes (40°–70°) and occasional polar spots, contributing to its variability as a BY Draconis [variable star](/source/Variable_star). [Chromospheric activity](/source/Chromospheric_activity) is high, with indicators like the Ca II H&K S-index averaging 0.644 and log R'HK of -4.08. The Rossby number is approximately 0.2, indicating strong convective dynamo action influenced by rotation.[14][9]

EK Draconis has been extensively studied as a proxy for the young Sun due to its age and solar-like properties.[17] In April 2020, astronomers observed a [superflare](/source/Superflare) using NASA's [Transiting Exoplanet Survey Satellite](/source/Transiting_Exoplanet_Survey_Satellite) (TESS) and the Kyoto University's SEIMEI Telescope, followed by a massive coronal mass ejection (CME).[15] The superflare was tens to hundreds of times more energetic than typical solar flares, and the subsequent CME expelled plasma with a mass in the quadrillions of kilograms—over 10 times larger than the most massive known solar CMEs. The ejecta traveled at speeds up to 500 km/s (about 1 million mph). This event, the first optical spectroscopic detection of a supermassive filament eruption on a Sun-like star, suggests that such phenomena were more common in the Sun's youth and could have influenced the atmospheres of early Solar System planets, such as stripping gas from proto-Mars.[14][11][12][13]

Multi-wavelength campaigns, including observations in 2021–2023, have further documented prominence eruptions associated with superflares, enhancing understanding of stellar space weather. Magnetic field mapping using instruments like ESPaDOnS and NARVAL from 2006 to 2012 has revealed the star's complex dynamo processes.[14][18]

## Significance

As a young Sun analog, EK Draconis provides insights into the Sun’s behavior ~4.5 billion years ago. Its rapid rotation and magnetic activity suggest the early Sun produced similar superflares and CMEs, potentially affecting the atmospheres of early Earth and Mars. The 2020 CME observation highlights implications for [planetary habitability](/source/Habitability_of_G-type_main-sequence_star_systems) in young stellar systems.[9]

## See also

- [Lists of stars](/source/Lists_of_stars)

- [List of star systems within 100–150 light-years](/source/List_of_star_systems_within_100%E2%80%93150_light-years)

## References

1. ^ [***a***](#cite_ref-dr3_1-0) [***b***](#cite_ref-dr3_1-1) [***c***](#cite_ref-dr3_1-2) [***d***](#cite_ref-dr3_1-3) [***e***](#cite_ref-dr3_1-4) [***f***](#cite_ref-dr3_1-5) 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%3D1668690628102524672%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-vsx_2-0) [***b***](#cite_ref-vsx_2-1) ["EK Draconis"](https://vsx.aavso.org/index.php?view=detail.top&oid=13826). *International Variable Star Index*. [AAVSO](/source/AAVSO). Retrieved 2025-09-25.

1. ^ [***a***](#cite_ref-yamashita2025_3-0) [***b***](#cite_ref-yamashita2025_3-1) [***c***](#cite_ref-yamashita2025_3-2) Yamashita, Mai; Itoh, Yoichi; Toriumi, Shin (2025). ["Variations in the Magnetic Field Strength of Pre-main-sequence Stars, Solar-type Main-sequence Stars, and the Sun"](https://doi.org/10.3847%2F1538-4357%2Fadc816). *The Astrophysical Journal*. **985** (1): 46. [arXiv](/source/ArXiv_(identifier)):[2504.04684](https://arxiv.org/abs/2504.04684). [Bibcode](/source/Bibcode_(identifier)):[2025ApJ...985...46Y](https://ui.adsabs.harvard.edu/abs/2025ApJ...985...46Y). [doi](/source/Doi_(identifier)):[10.3847/1538-4357/adc816](https://doi.org/10.3847%2F1538-4357%2Fadc816).

1. **[^](#cite_ref-nstars_4-0)** Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". *The Astronomical Journal*. **126** (4): 2048. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0308182](https://arxiv.org/abs/astro-ph/0308182). [Bibcode](/source/Bibcode_(identifier)):[2003AJ....126.2048G](https://ui.adsabs.harvard.edu/abs/2003AJ....126.2048G). [doi](/source/Doi_(identifier)):[10.1086/378365](https://doi.org/10.1086%2F378365). [S2CID](/source/S2CID_(identifier)) [119417105](https://api.semanticscholar.org/CorpusID:119417105).

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1. ^ [***a***](#cite_ref-Gorgei2025_6-0) [***b***](#cite_ref-Gorgei2025_6-1) [***c***](#cite_ref-Gorgei2025_6-2) [***d***](#cite_ref-Gorgei2025_6-3) Görgei, A.; Kriskovics, L.; Vida, K.; Seli, B.; Oláh, K.; Sági, P.; Bódi, A.; Järvinen, S. P.; Strassmeier, K. G. (2025-12-03). "Magnetic activity on the young Sun: a case study of EK Draconis". [arXiv](/source/ArXiv_(identifier)):[2512.03830](https://arxiv.org/abs/2512.03830) [[astro-ph.SR](https://arxiv.org/archive/astro-ph.SR)].

1. ^ [***a***](#cite_ref-loyd2014_7-0) [***b***](#cite_ref-loyd2014_7-1) Loyd, R. O. Parke; France, Kevin (2014). "Fluctuations and Flares in the Ultraviolet Line Emission of Cool Stars: Implications for Exoplanet Transit Observations". *The Astrophysical Journal Supplement Series*. **211** (1): 9. [arXiv](/source/ArXiv_(identifier)):[1402.0073](https://arxiv.org/abs/1402.0073). [Bibcode](/source/Bibcode_(identifier)):[2014ApJS..211....9L](https://ui.adsabs.harvard.edu/abs/2014ApJS..211....9L). [doi](/source/Doi_(identifier)):[10.1088/0067-0049/211/1/9](https://doi.org/10.1088%2F0067-0049%2F211%2F1%2F9). [S2CID](/source/S2CID_(identifier)) [118394892](https://api.semanticscholar.org/CorpusID:118394892).

1. **[^](#cite_ref-simbad_8-0)** ["EK Draconis"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=EK+Draconis). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2025-08-12.

1. ^ [***a***](#cite_ref-catalog_9-0) [***b***](#cite_ref-catalog_9-1) [***c***](#cite_ref-catalog_9-2) [***d***](#cite_ref-catalog_9-3) [***e***](#cite_ref-catalog_9-4) ["Star EK Draconis"](https://www.stellarcatalog.com/stars/ek-draconis). *Stellar Catalog*. Retrieved 1 March 2025.

1. **[^](#cite_ref-10)** ["Astronomers spy record-breaking eruption on young sunlike star"](https://www.space.com/sunlike-star-ek-draconis-superflare). *Space.Com*. 9 December 2021. Retrieved 1 March 2025.

1. ^ [***a***](#cite_ref-superflares_11-0) [***b***](#cite_ref-superflares_11-1) ["EK Draconis illuminates an unimagined picture of how superflares may affect interplanetary space through coronal mass ejections"](https://nso.edu/blog/researchers-observe-massive-cme-on-distant-sun-like-star/). *NSO*. 11 January 2022. Retrieved 1 March 2025.

1. ^ [***a***](#cite_ref-sunlike_12-0) [***b***](#cite_ref-sunlike_12-1) ["A young sun-like star may hold warnings for life on Earth"](https://www.colorado.edu/today/2021/12/09/ek-draconis). *University of Colorado Boulder*. Retrieved 1 March 2025.

1. ^ [***a***](#cite_ref-dragon_13-0) [***b***](#cite_ref-dragon_13-1) ["Fiery Dragon's Breath May Scorch Young Planets"](https://www.nao.ac.jp/en/news/science/2021/20211210-okayama.html). *NAOJ*. 10 December 2021. Retrieved 1 March 2025.

1. ^ [***a***](#cite_ref-waite2017_14-0) [***b***](#cite_ref-waite2017_14-1) [***c***](#cite_ref-waite2017_14-2) [***d***](#cite_ref-waite2017_14-3) [***e***](#cite_ref-waite2017_14-4) Waite, I. A.; Marsden, S. C.; Carter, B. D.; Petit, P.; Jeffers, S. V.; Morin, J.; Vidotto, A. A.; Donati, J. -F.; BCool Collaboration (2017). ["Magnetic fields on young, moderately rotating Sun-like stars - II. EK Draconis (HD 129333)"](https://doi.org/10.1093%2Fmnras%2Fstw2731). *Monthly Notices of the Royal Astronomical Society*. **465** (2): 2076. [arXiv](/source/ArXiv_(identifier)):[1611.07751](https://arxiv.org/abs/1611.07751). [Bibcode](/source/Bibcode_(identifier)):[2017MNRAS.465.2076W](https://ui.adsabs.harvard.edu/abs/2017MNRAS.465.2076W). [doi](/source/Doi_(identifier)):[10.1093/mnras/stw2731](https://doi.org/10.1093%2Fmnras%2Fstw2731).

1. ^ [***a***](#cite_ref-konig2005_15-0) [***b***](#cite_ref-konig2005_15-1) König, B.; Guenther, E. W.; Woitas, J.; Hatzes, A. P. (2005). "The young active binary star EK Draconis". *Astronomy and Astrophysics*. **435** (1): 215. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0501608](https://arxiv.org/abs/astro-ph/0501608). [Bibcode](/source/Bibcode_(identifier)):[2005A&A...435..215K](https://ui.adsabs.harvard.edu/abs/2005A&A...435..215K). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20040462](https://doi.org/10.1051%2F0004-6361%3A20040462).

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1. **[^](#cite_ref-17)** Namekata, Kosuke; Ikuta, Kai; Petit, Pascal; Airapetian, Vladimir S.; Vidotto, Aline A.; Heinzel, Petr; Wollmann, Jiří; Maehara, Hiroyuki; Notsu, Yuta; Inoue, Shun; Marsden, Stephen; Morin, Julien; Jeffers, Sandra V.; Neiner, Coralie; Paudel, Rishi R.; Avramova-Boncheva, Antoaneta A.; Gendreau, Keith; Shibata, Kazunari (2024). ["Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. II. Understanding Prominence Eruption through Data-driven Modeling and Observed Magnetic Environment"](https://doi.org/10.3847%2F1538-4357%2Fad85df). *The Astrophysical Journal*. **976** (2): 255. [arXiv](/source/ArXiv_(identifier)):[2410.05523](https://arxiv.org/abs/2410.05523). [Bibcode](/source/Bibcode_(identifier)):[2024ApJ...976..255N](https://ui.adsabs.harvard.edu/abs/2024ApJ...976..255N). [doi](/source/Doi_(identifier)):[10.3847/1538-4357/ad85df](https://doi.org/10.3847%2F1538-4357%2Fad85df).

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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 [EK Draconis](https://en.wikipedia.org/wiki/EK_Draconis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/EK_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.