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  • 21 Aug, 2019

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Epsilon Draconis

Epsilon Draconis, Latinized from ε Draconis, is a binary star in the constellation Draco, with a combined apparent magnitude of 3.84, it is the eleventh-brightest star in this rather faint constellation. This star along with Delta Draconis (Altais), Pi Draconis and Rho Draconis forms an asterism known as Al Tāis, meaning "the Goat". The distance to this system has been measured at about 150 light-years, based on stellar parallax measurements.

In Chinese astronomy, 天廚 (Tiān Chú), meaning the Celestial Kitchen, refers to an asterism consisting of Epsilon Draconis, Delta Draconis, Sigma Draconis, Rho Draconis, 64 Draconis and Pi Draconis. Consequently, the Chinese name for Epsilon Draconis itself is 天廚三 (Tiān Chú sān, English: the Third Star of the Celestial Kitchen.) Most authors do not use a traditional name for this star, using instead the Bayer designation; but Bečvář (1951) listed it as Tyl /ˈtɪl/.

Visibility

With a declination in excess of 70 degrees north, Epsilon Draconis is principally visible in the northern hemisphere, with southern locations north of 20° South able to see it just above the horizon. The star is circumpolar throughout all of Europe, China, most of India and as far south as the tip of the Baja peninsula in North America as well as other locations around the globe having a latitude greater than about 20° North. Since Epsilon Draconis has an apparent magnitude of almost 4.0, the star is easily observable to the naked eye as long as one's stargazing is not hampered by the light pollution common to most cities.

The best time for observation is in the evening sky during the summer months, when the "Dragon constellation" passes the meridian at midnight, but given its circumpolar nature in the northern hemisphere, it is visible to most of the world's inhabitants throughout the year.

Properties

Epsilon Draconis is a binary star, whose components can be split in a telescope. They are separated by 3.2 arcseconds as of 2012, translating to a projected separation of 145 astronomical units.

The primary of the system has a spectral type of G7IIIbFe-1, which classify it as a is a yellow giant star, a star which ran out of hydrogen at its core and expanded in size. It is visible with apparent magnitude of 3.91. Asteroseismology of this star retrieve a mass of 1.20 solar masses and a radius over ten times solar. Other estimates suggest masses between 1.5 and 2 solar masses. This star's abundance of elements heavier than helium relative to hydrogen, what astronomers term metallicity, is just half of the Sun's. The effective temperature of the star is 4,966 K, roughly 800 degrees cooler than the Sun. It seems to have already enabled helium fusion at its core, being a red clump star.

The secondary is a F-type main-sequence star of class F6V, fusing hydrogen into helium at its core. It has an apparent magnitude 6.8 and is 14 times fainter than the primary. This star is about 20% times larger, three times brighter and about 1,100 degrees hotter than the Sun.

See also

Notes

  1. ^ The abundance is estimated by taking [M/H] to the power of ten:
              10 = 10 = 0.49

References

  1. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ "eps Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved January 26, 2025.
  3. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  4. ^ "eps Dra B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved January 26, 2025.
  5. ^ 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:1989ApJS...71..245K. doi:10.1086/191373. Epsilon Draconis' database entry at VizieR.
  6. ^ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. SIMBAD. Bibcode:1986EgUBV........0M.
  7. ^ Eggleton, P. P.; Tokovinin, A. A. (2008-09-01). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. ISSN 0035-8711. Epsilon Draconis' database entry at VizieR.
  8. ^ Hon, Marc; Kuszlewicz, James S.; Huber, Daniel; Stello, Dennis; Reyes, Claudia (2022-10-01). "HD-TESS: An Asteroseismic Catalog of Bright Red Giants within TESS Continuous Viewing Zones". The Astronomical Journal. 164 (4): 135. arXiv:2208.06478. Bibcode:2022AJ....164..135H. doi:10.3847/1538-3881/ac8931. ISSN 0004-6256. Epsilon Draconis' database entry at VizieR.
  9. ^ Luck, R. Earle (2015-09-01). "Abundances in the Local Region. I. G and K Giants". The Astronomical Journal. 150 (3): 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88. ISSN 0004-6256. Epsilon Draconis' database entry at VizieR.
  10. ^ Tautvaišienė, G.; Mikolaitis, Š.; Drazdauskas, A.; Stonkutė, E.; Minkevičiūtė, R.; Kjeldsen, H.; Brogaard, K.; von Essen, C.; Grundahl, F.; Pakštienė, E.; Bagdonas, V.; Viscasillas Vázquez, C. (2020-05-01). "Chemical Composition of Bright Stars in the Continuous Viewing Zone of the TESS Space Mission". The Astrophysical Journal Supplement Series. 248 (1): 19. arXiv:2005.07526. Bibcode:2020ApJS..248...19T. doi:10.3847/1538-4365/ab8b67. ISSN 0067-0049. Epsilon Draconis' database entry at VizieR.
  11. ^ Strassmeier, K. G.; Weber, M.; Gruner, D.; Ilyin, I.; Steffen, M.; Baratella, M.; Järvinen, S.; Granzer, T.; Barnes, S. A.; Carroll, T. A.; Mallonn, M.; Sablowski, D.; Gabor, P.; Brown, D.; Corbally, C. (2023-03-01). "VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole - I. Survey design, pilot analysis, and initial data release". Astronomy & Astrophysics. 671: A7. arXiv:2302.01794. Bibcode:2023A&A...671A...7S. doi:10.1051/0004-6361/202245255. ISSN 0004-6361. Epsilon Draconis' database entry at VizieR.
  12. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  13. ^ Ducati, J. R. (2002-01-01). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR Online Data Catalog. 2237. Bibcode:2002yCat.2237....0D.
  14. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 209. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  15. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  16. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived August 19, 2010, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. ^ Kaler, Jim. "Epsilon Draconis". Retrieved 2016-11-24.
  18. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  19. ^ Bakich, Michael (1995). The Cambridge Guide to the Constellations. Cambridge University Press. p. 202. ISBN 0521449219. Retrieved 2016-11-24. Tyl.