epsilon Draconis

{{Starbox image

| image=

{{Location mark

| image=Draco constellation map.svg

| float=center | width=250 | position=right

| mark=Red circle.svg | mark_width=10 | mark_link=Epsilon Dra

| x%=16.6 | y%=40.6

}}

| caption=Location of ε Draconis (circled)

}}

{{Starbox observe 2s

| epoch = J2000

| constell = Draco

| component1 = A

| ra1 = {{RA|19|48|10.35046}}

| dec1 = {{DEC|+70|16|04.5491}}

| appmag_v1 = 3.91

| component2 = B

| ra2 = {{RA|19|48|10.54875}}

| dec2 = {{DEC|+70|16|07.5676}}

| appmag_v2 = 6.80

}}

{{Starbox character

| component1 = A

| type = red clump

| class = G7IIIbFe-1{{cite journal | bibcode=1989ApJS...71..245K | title=The Perkins catalog of revised MK types for the cooler stars | journal=Astrophysical Journal Supplement Series | volume=71 | pages=245 | last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C. | year=1989 | doi=10.1086/191373 }} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=III/150&Name=HD%20188119 Epsilon Draconis' database entry] at VizieR.

| b-v = +0.88 {{cite journal| author=Mermilliod, J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV Data. SIMBAD | year=1986 | bibcode=1986EgUBV........0M}}

| u-b = +0.48

| variable =

| component2 = B

| b-v2 = 0.57

| class2 = F6V

}}

{{Starbox astrometry

| component1 = A

| radial_v = {{val|+2.89|0.11}}

| prop_mo_ra = +79.486

| prop_mo_dec = +40.041

| pm_footnote =

| parallax = 21.3219

| p_error = 0.1256

| parallax_footnote =

| component2 = B

| radial_v2 =

| prop_mo_ra2 = +86.898

| prop_mo_dec2 = +37.126

| pm_footnote2 =

| parallax2 = 21.3808

| p_error2 = 0.0403

| parallax_footnote2 =

}}

{{Starbox detail

| component1 = A

| mass = {{val|1.20|0.08}}, {{val|1.76|0.29|0.23}}

| radius = {{val|10.41|0.29}}

| luminosity = 63.1

| temperature = {{Val|4966|41|fmt=commas}}

| metal = {{M/H|-0.31}}

| metal_fe = {{val|-0.30}}

| gravity = 2.61

| rotational_velocity = {{Val|2.25|0.56}}

| age_gyr = {{val|2.6|1.8|1.6}}

| component2 = B

| radius2 = 1.16

| temperature2 = 6,936

| luminosity2 = 2.814

}}

{{Starbox catalog

| names = {{odlist | name=Tyl | B=ε Dra | F=63 Dra | HR=7582 | AG=+70°689 | BD=+69°1070 | HD=188119 | HIP=97433 | PLX=4689 | SAO=9540 | GC=27471 | CCDM=J19482+7016AB | 2MASS=J19481035+7016045 | IRAS=19483+7008 }}

}}

{{Starbox reference

|Simbad=HD+188119}}

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".{{cite book

| last=Allen

| first=R. H.

| year=1963

| author-link=Richard Hinckley Allen

| title=Star Names: Their Lore and Meaning

| url=https://archive.org/details/starnamestheirlo00alle/page/209

| access-date=2010-12-12

| edition=Reprint

| publisher=Dover Publications Inc

| location=New York, NY

| isbn=0-486-21079-0

| page=[https://archive.org/details/starnamestheirlo00alle/page/209 209]

| url-access=registration

}} The distance to this system has been calculated to be about {{val|150|u=light-years}}, based on stellar parallax measurements.

In Chinese astronomy, {{lang|zh|天廚}} ({{lang|zh-Latn|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.{{in lang|zh}} 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}}. Consequently, the Chinese name for Epsilon Draconis itself is {{lang|zh|天廚三}} ({{lang|zh-Latn|Tiān Chú sān}}, {{langx|en|the Third Star of the Celestial Kitchen}}.){{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_t_z.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive |url=https://web.archive.org/web/20100819122914/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_t_z.htm |date=August 19, 2010 }}, Hong Kong Space Museum. Accessed on line November 23, 2010. Most authors do not use a traditional name for this star, using instead the Bayer designation;{{cite web

|title=Epsilon Draconis

|first=Jim|last=Kaler

|url=http://stars.astro.illinois.edu/sow/epsdra.html

|access-date=2016-11-24}}

but Bečvář (1951) listed it as Tyl {{IPAc-en|'|t|I|l}}.{{cite book

|last1=Kunitzsch |first1=Paul

|last2=Smart |first2=Tim

|date = 2006 |edition = 2nd rev.

|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations

|publisher = Sky Pub |location = Cambridge, Massachusetts

|isbn = 978-1-931559-44-7

}}{{cite book

|last=Bakich

|first=Michael

|date=1995

|title=The Cambridge Guide to the Constellations

|url=https://archive.org/details/cambridgeguideto00baki

|url-access=registration

|quote=Tyl.

|publisher=Cambridge University Press

|page=[https://archive.org/details/cambridgeguideto00baki/page/202 202]

|access-date=2016-11-24

|isbn=0521449219}}

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 {{val|3.2|u=arcseconds}} as of 2012, translating to a projected separation of {{val|145|u=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 {{val|1.20|u=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.{{efn|name=metal}} The effective temperature of the star is {{val|4966|fmt=commas|ul=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.

Notes

{{notelist|refs=

{{efn|name=metal|1 = The abundance is estimated by taking [M/H] to the power of ten:{{indent|10}}10^[M/H] = 10^−0.31 = 0.49}}

}}

References

{{reflist|refs=

{{Cite journal |last1=Strassmeier |first1=K. G. |last2=Weber |first2=M. |last3=Gruner |first3=D. |last4=Ilyin |first4=I. |last5=Steffen |first5=M. |last6=Baratella |first6=M. |last7=Järvinen |first7=S. |last8=Granzer |first8=T. |last9=Barnes |first9=S. A. |last10=Carroll |first10=T. A. |last11=Mallonn |first11=M. |last12=Sablowski |first12=D. |last13=Gabor |first13=P. |last14=Brown |first14=D. |last15=Corbally |first15=C. |date=2023-03-01 |title=VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole - I. Survey design, pilot analysis, and initial data release |journal=Astronomy & Astrophysics |language=en |volume=671 |pages=A7 |doi=10.1051/0004-6361/202245255 |arxiv=2302.01794 |bibcode=2023A&A...671A...7S |issn=0004-6361}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/164/135&TIC=279979429 Epsilon Draconis' database entry] at VizieR.

{{Cite journal |last1=Tautvaišienė |first1=G. |last2=Mikolaitis |first2=Š. |last3=Drazdauskas |first3=A. |last4=Stonkutė |first4=E. |last5=Minkevičiūtė |first5=R. |last6=Kjeldsen |first6=H. |last7=Brogaard |first7=K. |last8=von Essen |first8=C. |last9=Grundahl |first9=F. |last10=Pakštienė |first10=E. |last11=Bagdonas |first11=V. |last12=Viscasillas Vázquez |first12=C. |date=2020-05-01 |title=Chemical Composition of Bright Stars in the Continuous Viewing Zone of the TESS Space Mission |journal=The Astrophysical Journal Supplement Series |volume=248 |issue=1 |pages=19 |doi=10.3847/1538-4365/ab8b67 |doi-access=free |arxiv=2005.07526 |bibcode=2020ApJS..248...19T |issn=0067-0049}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/ApJS/248/19&TIC=279979429 Epsilon Draconis' database entry] at VizieR.

{{Cite journal |last1=Hon |first1=Marc |last2=Kuszlewicz |first2=James S. |last3=Huber |first3=Daniel |last4=Stello |first4=Dennis |last5=Reyes |first5=Claudia |date=2022-10-01 |title=HD-TESS: An Asteroseismic Catalog of Bright Red Giants within TESS Continuous Viewing Zones |journal=The Astronomical Journal |volume=164 |issue=4 |pages=135 |doi=10.3847/1538-3881/ac8931 |doi-access=free |arxiv=2208.06478 |bibcode=2022AJ....164..135H |issn=0004-6256}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/164/135&TIC=279979429 Epsilon Draconis' database entry] at VizieR.

{{Cite journal |last=Luck |first=R. Earle |date=2015-09-01 |title=Abundances in the Local Region. I. G and K Giants |journal=The Astronomical Journal |volume=150 |issue=3 |pages=88 |doi=10.1088/0004-6256/150/3/88 |arxiv=1507.01466 |bibcode=2015AJ....150...88L |issn=0004-6256}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/150/88&Name=*%20eps%20Dra Epsilon Draconis' database entry] at VizieR.

{{Cite journal |last=Ducati |first=J. R. |date=2002-01-01 |title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system. |bibcode=2002yCat.2237....0D |journal=VizieR Online Data Catalog |volume=2237}}

{{Cite journal |last1=Eggleton |first1=P. P. |last2=Tokovinin |first2=A. A. |date=2008-09-01 |title=A catalogue of multiplicity among bright stellar systems |journal=Monthly Notices of the Royal Astronomical Society |volume=389 |issue=2 |pages=869–879 |doi=10.1111/j.1365-2966.2008.13596.x |doi-access=free |arxiv=0806.2878 |bibcode=2008MNRAS.389..869E |issn=0035-8711}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/MNRAS/389/869&mHR=7582 Epsilon Draconis' database entry] at VizieR.

}}

External links

Astrophotographs:[http://www.asociacionhubble.org/portal/index.php/foro/viewtopic.php?f=63&t=16459&start=50 Epsilon Draconis]
SkyView Image: [http://skyview.gsfc.nasa.gov/cgi-bin/nnskcall.pl?VCOORD=297.0431337500000382,+70.2679302777777792&SURVEY=Digitized+Sky+Survey&SCOORD=&EQUINX=2000&LUT=colortables/stern-special.bin Epsilon Draconis]

Category:G-type giants

Category:Double stars

Category:Draco (constellation)

Category:Horizontal-branch stars

epsilon Draconis

Visibility

Properties

See also

Notes

References

External links