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Epsilon Draconis - Wikipedia

Coordinates:

19^h 48^m 10.35^s, +70° 16′ 04.55″

From Wikipedia, the free encyclopedia

Epsilon Draconis
Observation data Epoch J2000 Equinox J2000
Location of ε Draconis (circled)
Constellation	Draco
Right ascension	19^h 48^m 10.34973^s^[1]
Declination	70° 16′ 04.5329″^[1]
Apparent magnitude (V)	3.9974^[2]
Characteristics
Spectral type	G7IIIbFe-1^[3]
U−B color index	+0.48^[4]
B−V color index	+0.88 ^[4]
Astrometry

Radial velocity (R_v)	+2.69±0.23^[5] km/s
Proper motion (μ)	RA: +79.702^[1] mas/yr Dec.: +41.078^[1] mas/yr
Parallax (π)	21.2526 ± 0.3016 mas^[1]
Distance	153 ± 2 ly (47.1 ± 0.7 pc)
Absolute magnitude (M_V)	0.71^[2]

Details

Mass	2.7^[6]^[7] `M`_☉
Radius	11.15+0.47 −0.56^[1] `R`_☉
Luminosity	69.6±1.12^[1] `L`_☉
Temperature	4993+129 −103^[1] K
Metallicity [Fe/H]	-0.31^[8] dex
Rotational velocity (v sin i)	1.2 ^[6] km/s
Age	500^[6] Myr

Other designations
Tyl, ε Dra, 63 Dra, AG+70° 689, BD+69° 1070, GC 27471, HD 188119, HIP 97433, HR 7582, SAO 9540, CCDM J19482+7016AB, PLX 4689, IRAS 19483+7008, 2MASS J19481035+7016045^[9]
Database references
SIMBAD	data

Epsilon Draconis, Latinized from ε Draconis, is a fourth-magnitude star in the constellation Draco. This star along with Delta Draconis (Altais), Pi Draconis and Rho Draconis forms an asterism known as Al Tāis, meaning "the Goat".^[10]

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.^[11] Consequently, the Chinese name for Epsilon Draconis itself is 天廚三 (Tiān Chú sān, English: the Third Star of the Celestial Kitchen.)^[12] Most authors do not use a traditional name for this star, using instead the Bayer designation;^[13] but Bečvář (1951) listed it as Tyl /ˈtɪl/.^[14]^[15]

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 ± 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 yellow giant star with a spectral type of G8III. It has a radius that has been estimated at 11 solar radii and a mass of 2.7 solar masses.^[6] Compared to most G class stars, Epsilon Draconis is a relatively young star with an estimated age of around 500 million years old.^[6] Like the majority of giant stars, Epsilon Draconis rotates slowly on its axis with a rotational velocity of 1.2 km/s, a speed which takes the star approximately 420 days to make one complete revolution.^[6]

In 2007, Floor van Leeuwen and his team calibrated the star's apparent magnitude at 3.9974 with an updated parallax of 22.04 ± 0.37 milliarcseconds, yielding a distance of 45.4 parsecs or approximately 148 light years from Earth.^[2] Given a surface temperature of 5,068 Kelvin, theoretical calculations would yield a total luminosity for the star of about 60 times the solar luminosity.

Star system

Epsilon Draconis is resolvable as a double star in telescopes of 10 centimeters aperture or larger. The companion has an apparent brightness of 7.3 at an angular distance of 3.2 arcseconds. It is a giant of spectral class F5,^[9] orbiting the yellow giant at about 130 astronomical units.^{[citation needed]}

References

^ ^a ^b ^c ^d ^e ^f ^g ^h 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.
^ ^a ^b ^c van Leeuwen, F (November 2007). "Hipparcos, the New Reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Retrieved 2010-12-18.
^ 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.
^ ^a ^b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. SIMBAD. Bibcode:1986EgUBV........0M.
^ Soubiran, C.; et al. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. arXiv:0712.1370. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788. S2CID 16602121.
^ ^a ^b ^c ^d ^e ^f Mallik, Sushma V.; Parthasarathy, M.; Pati, A. K. (October 2003). "Li abundances and velocities in F and G stars". VizieR. Centre de Données astronomiques de Strasbourg. Retrieved 2010-12-18.
^ Mallik, Sushma V.; Parthasarathy, M.; Pati, A. K. (October 2003). "Lithium and rotation in F and G dwarfs and subgiants". Astronomy and Astrophysics. 409 (1): 251–261. Bibcode:2003A&A...409..251M. doi:10.1051/0004-6361:20031084. Retrieved 2010-12-18.
^ Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. arXiv:0712.1370. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788. S2CID 16602121.
^ ^a ^b "* eps Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-12-18.
^ 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.
^ (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.
^ (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.
^ Kaler, Jim. "Epsilon Draconis". Retrieved 2016-11-24.
^ 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.
^ Bakich, Michael (1995). The Cambridge Guide to the Constellations. Cambridge University Press. p. 202. ISBN 0521449219. Retrieved 2016-11-24. Tyl.

External links

Astrophotographs:Epsilon Draconis
SkyView Image: Epsilon Draconis

Constellation of Draco

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	6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 64 (e) 68
Variable	TW AG BY CL CM CX DO V581
HR	3751 4126 4934 5811 6237 6618 (Alruba) 6817 7137 7783
HD	101364 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 LP 71-82 Qatar-1 Struve 2398 TOI-1136 WISE 1647+5632

Exoplanets	Orbitar HD 139357 b HD 167042 b Hypatia Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i TOI-1452 b TrES-2b

Star clusters	LAMOST 1

Nebulae	Abell 50 Cat's Eye Nebula

Galaxies

NGC	3147 4121 4125 4236 4319 4345 4513 4589 5678 5777 5866 5866B 5879 5906 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6338 6340 6365 6373 6394 6412 6503 6566 6621 6622 6670 6676 6786 6789
Other	1ES 1959+650 3C 249.1 3C 305 3C 319 3C 356 3C 371 3C 390.3 3C 401 4C +72.26 H1821+643 HFLS3 KKR 25 Markarian 876 PGC 39058 S5 1803+784 S5 2007+777 UGC 9391

Galaxy clusters	Abell 2218 CL1358+62 Draco Supercluster

Astronomical events	Swift J1644+57 SN 2005B SN 2016aps

Visibility

Properties

Star system

See also

References

External links