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Coordinates: Sky map 14h 04m 23.3498s, +64° 22′ 33.062″
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| ra={{RA|14|04|23.3500}}<ref name=hipparcos/>
| ra={{RA|14|04|23.3500}}<ref name=hipparcos/>
| dec={{DEC|64|22|33.062}}<ref name=hipparcos/>
| dec={{DEC|64|22|33.062}}<ref name=hipparcos/>
| appmag_v=3.67<ref name=Anderson_Francis_2012>{{citation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 | postscript=. }}</ref>
| appmag_v=3.67<ref name=Anderson_Francis_2012>{{cite journal| last1=Anderson | first1=E. | last2=Francis | first2=Ch. | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 }}</ref>
| constell=[[Draco (constellation)|Draco]]
| constell=[[Draco (constellation)|Draco]]
}}
}}
{{Starbox character
{{Starbox character
| class=A0III<ref name=mk/>
| class=A0IV + A1V<ref name=Pavlovski/>
| b-v={{val|−0.049|0.005}}<ref name=Anderson_Francis_2012/>
| b-v={{val|−0.049|0.005}}<ref name=Anderson_Francis_2012/>
| u-b=−0.08
| u-b=−0.08
⚫
| variable=suspected [[Maia variable|Maia]]<ref name=kallinger>{{Cite journal | doi = 10.1017/S1743921305009865| title = The puzzling Maia candidate star α Draconis| year = 2005| last1 = Kallinger | first1 = T. | last2 = Iliev | first2 = I.| last3 = Lehmann | first3 = H.| last4 = Weiss | first4 = W. W. | journal = Proceedings of the International Astronomical Union| volume = 2004| pages = 848–852| bibcode = 2004IAUS..224..848K| doi-access = free}}</ref>
| variable=suspected [[Maia variable|Maia]]<ref name=kallinger/>
}}
}}
{{Starbox astrometry
{{Starbox astrometry
Line 34: Line 34:
| p_error=0.17
| p_error=0.17
|parallax_footnote=<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref>
|parallax_footnote=<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref>
|absmag_v=−1.20<ref name=murphy>{{cite journal|bibcode=2017MNRAS.466..546M|arxiv=1612.01528|title=Gaia's view of the λ Boo star puzzle|journal=Monthly Notices of the Royal Astronomical Society|volume=466|issue=1|pages=546|last1=Murphy|first1=Simon J.|last2=Paunzen|first2=Ernst|year=2017|doi=10.1093/mnras/stw3141|s2cid=119328659}}</ref>
|absmag_v=−1.20<ref name=murphy>{{cite journal|bibcode=2017MNRAS.466..546M|arxiv=1612.01528|title=Gaia's view of the λ Boo star puzzle|journal=Monthly Notices of the Royal Astronomical Society|volume=466|issue=1|pages=546|last1=Murphy|first1=Simon J.|last2=Paunzen|first2=Ernst|year=2017|doi=10.1093/mnras/stw3141|doi-access=free |s2cid=119328659}}</ref>
}}
}}
{{Starbox orbit
{{Starbox orbit
| reference = <ref name=Pavlovski>{{cite journal|doi=10.1051/0004-6361/202142292|title=Dynamical parallax, physical parameters, and evolutionary status of the components of the bright eclipsing binary α Draconis|year=2022|last1=Pavlovski|first1=K.|last2=Hummel|first2=C. A.|last3=Tkachenko|first3=A.|last4=Dervişoğlu|first4=A.|last5=Kayhan|first5=C.|last6=Zavala|first6=R. T.|last7=Hutter|first7=D. J.|last8=Tycner|first8=C.|last9=Şahin|first9=T.|last10=Audenaert|first10=J.|last11=Baeyens|first11=R.|last12=Bodensteiner|first12=J.|last13=Bowman|first13=D. M.|last14=Gebruers|first14=S.|last15=Jannsen|first15=N. E.|last16=Mombarg|first16=J. S. G.|journal=Astronomy & Astrophysics|volume=658|pages=A92|arxiv=2111.03887|bibcode=2022A&A...658A..92P|s2cid=243847585}}</ref>
| reference =
| period_unitless = 51.417350 d
| period_unitless = 51.4167 days<ref name=behr>{{cite journal|bibcode=2009ApJ...705..543B|arxiv=0909.3241|title=Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. I. Instrument Description and Orbits of Single-lined Spectroscopic Binaries|journal=The Astrophysical Journal|volume=705|issue=1|pages=543–553|last1=Behr|first1=Bradford B.|last2=Hajian|first2=Arsen R.|last3=Cenko|first3=Andrew T.|last4=Murison|first4=Marc|last5=McMillan|first5=Robert S.|last6=Hindsley|first6=Robert|last7=Meade|first7=Jeff|year=2009|doi=10.1088/0004-637X/705/1/543|s2cid=17966103}}</ref>
| periastron = JD&nbsp;2453498.8
| axis =
| eccentricity = 0.4355 ± 0.0042<ref name=behr/>
| eccentricity = 0.43
| periarg = 22.4
| k1 = 47.9340 ± 0.2990<ref name=behr/>
| node = 252.6
⚫
| inclination = 90<ref name=kallinger/>
| inclination = 85.4
| axis_unitless = 0.46 AU<ref name=kallinger/>
| axis_unitless = 5.52 mas
| k1 = 48.512
| k2 = 63.58
}}
}}
{{Starbox detail
{{Starbox detail
⚫
| source = <ref name=Pavlovski/>
| component1 = α Dra A
| component1 = α Draconis A<br />Alpha Draconis A
⚫
| mass=2.8<ref name=kallinger>{{Cite journal | doi = 10.1017/S1743921305009865| title = The puzzling Maia candidate star α Draconis| year = 2005| last1 = Kallinger | first1 = T. | last2 = Iliev | first2 = I.| last3 = Lehmann | first3 = H.| last4 = Weiss | first4 = W. W. | journal = Proceedings of the International Astronomical Union| volume = 2004| pages = 848–852| bibcode = 2004IAUS..224..848K| doi-access = free}}</ref>
| mass = 3.186
| luminosity=479<ref name=balona/>
| radius = 4.932
| radius=3.4<ref name=wesselink>{{cite journal|bibcode=1972A&AS....7..257W|title=Catalogue of stellar dimensions|journal=Astronomy and Astrophysics Supplement|volume=7|pages=257|last1=Wesselink|first1=A. J.|last2=Paranya|first2=K.|last3=Devorkin|first3=K.|year=1972}}</ref>
| gravity = 3.555
| temperature=10,100<ref name=balona>{{cite journal|bibcode=2016MNRAS.460.1318B|arxiv=1606.06426|title=The hot γ Doradus and Maia stars|journal=Monthly Notices of the Royal Astronomical Society|volume=460|issue=2|pages=1318|last1=Balona|first1=L. A.|last2=Engelbrecht|first2=C. A.|last3=Joshi|first3=Y. C.|last4=Joshi|first4=S.|last5=Sharma|first5=K.|last6=Semenko|first6=E.|last7=Pandey|first7=G.|last8=Chakradhari|first8=N. K.|last9=Mkrtichian|first9=David|last10=Hema|first10=B. P.|last11=Nemec|first11=J. M.|year=2016|doi=10.1093/mnras/stw1038|s2cid=119164509}}</ref>
| temperature = 10225
| gravity=3.5<ref name=gray/>
| luminosity = 240<!-- log(L) = 2.380 -->
| metal=−0.20<ref name=gray/>
| rotational_velocity = 25.4
| rotation=26.2<ref name=gray>{{Cite journal|bibcode=2014AJ....147...81G|title=Precise Rotation Rates for Five Slowly Rotating a Stars|journal=The Astronomical Journal|volume=147|issue=4|pages=81|last1=Gray|first1=David F.|year=2014|doi=10.1088/0004-6256/147/4/81}}</ref>
| component2 = α Dra B
| age_myr = 280
| component2 = α Draconis B<br />Alpha Draconis B
| mass2 = 2.6<ref name=behr/>
| mass2 = 2.431
⚫
| luminosity2 = 40<ref name=behr/>
| age_gyr =
| radius2 = 2.326
| gravity2 = 4.090
| temperature2 = 9930
⚫
| luminosity2 = 47.5<!-- log(L) = 1.677 -->
| rotational_velocity2 = 168
| age_myr2 = 345
}}
}}
{{Starbox catalog
{{Starbox catalog
Line 84: Line 92:
The traditional name ''Thuban'' is derived from the [[Arabic]] word {{lang|ar|ثعبان}} ''{{transl|ar|DIN|thuʿbān}}'' ('large snake' (e.g. a python or a legendary draconian serpent)). It is sometimes known as the ''Dragon's Tail'' and as ''Adib'' {{IPAc-en|@|'|d|iː|b}}.<ref name=Kunitzsch/> In 2016, the [[International Astronomical Union]] organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> included a table of the first two batches of names approved by the WGSN; which included ''Thuban'' for this star. It is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref>
The traditional name ''Thuban'' is derived from the [[Arabic]] word {{lang|ar|ثعبان}} ''{{transl|ar|DIN|thuʿbān}}'' ('large snake' (e.g. a python or a legendary draconian serpent)). It is sometimes known as the ''Dragon's Tail'' and as ''Adib'' {{IPAc-en|@|'|d|iː|b}}.<ref name=Kunitzsch/> In 2016, the [[International Astronomical Union]] organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> included a table of the first two batches of names approved by the WGSN; which included ''Thuban'' for this star. It is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref>


In [[Chinese astronomy|Chinese]], {{lang|zh|紫微右垣}} ({{lang|zh-Latn|Zǐ Wēi Yòu Yuán}}), meaning ''[[Purple Forbidden enclosure|Right Wall of Purple Forbidden Enclosure]]'', refers to an [[Asterism (astronomy)|asterism]] consisting of Alpha Draconis, [[Kappa Draconis]], [[Lambda Draconis]], [[24 Ursae Majoris]], [[43 Camelopardalis]], [[Alpha Camelopardalis]] and [[BK Camelopardalis]].<ref>{{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}}.</ref> Consequently, the [[Chinese star name|Chinese name]] for Alpha Draconis itself is {{lang|zh|紫微右垣一}} ({{lang|zh-Latn|Zǐ Wēi Yòu Yuán yī}}, {{lang-en|the First Star of Right Wall of Purple Forbidden Enclosure}}),<ref>{{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=2010-08-19 }}, Hong Kong Space Museum. Retrieved 2010-11-23.</ref> representing {{lang|zh|右樞}} ({{lang|zh-Latn|Yòushū}}), meaning ''Right Pivot''.<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name] {{webarchive|url=https://web.archive.org/web/20100810114313/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm |date=2010-08-10 }}, Hong Kong Space Museum. Retrieved 2010-11-23.</ref> 右樞 (Yòushū) is westernized into ''Yu Choo'' by R.H. Allen with the same meaning.<ref name="ALLEN">{{Cite web
In [[Chinese astronomy|Chinese]], {{lang|zh|紫微右垣}} ({{lang|zh-Latn|Zǐ Wēi Yòu Yuán}}), meaning ''[[Purple Forbidden enclosure|Right Wall of Purple Forbidden Enclosure]]'', refers to an [[Asterism (astronomy)|asterism]] consisting of Alpha Draconis, [[Kappa Draconis]], [[Lambda Draconis]], [[24 Ursae Majoris]], [[43 Camelopardalis]], [[Alpha Camelopardalis]] and [[BK Camelopardalis]].<ref>{{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}}.</ref> Consequently, the [[Chinese star name|Chinese name]] for Alpha Draconis itself is {{lang|zh|紫微右垣一}} ({{lang|zh-Latn|Zǐ Wēi Yòu Yuán yī}}, {{langx|en|the First Star of Right Wall of Purple Forbidden Enclosure}}),<ref>{{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=2010-08-19 }}, Hong Kong Space Museum. Retrieved 2010-11-23.</ref> representing {{lang|zh|右樞}} ({{lang|zh-Latn|Yòushū}}), meaning ''Right Pivot''.<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm#PrupleForbiddenEnclosure English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name] {{webarchive|url=https://web.archive.org/web/20100810114313/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/e_research_chinengstarzone_b.htm |date=2010-08-10 }}, Hong Kong Space Museum. Retrieved 2010-11-23.</ref>
| title=Star Names: Their Lore and Meaning
| work=Dover Publications
| author=Richard Hinckley Allen
| page=210
| year=1963
| access-date=2010-12-17
|url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html
| author-link=Richard Hinckley Allen}}</ref>


== Visibility ==
== Visibility ==
Given good viewing conditions, Thuban is relatively easy to spot in the night sky, due to its location in relation to the [[Big Dipper]] (aka the Plough) [[Asterism (astronomy)|asterism]] of [[Ursa Major]]. While it is well known that the two outer stars of the 'dipper' point to the modern-day [[pole star]] [[Polaris]], it is less well known that the two inner stars, [[Gamma Ursae Majoris|Phecda]] and [[Delta Ursae Majoris|Megrez]], point to Thuban, just 15 degrees of arc from Megrez. Thuban is not bright enough to be viewed from badly [[light pollution|light-polluted]] areas.
Given good viewing conditions, Thuban is relatively easy to spot in the night sky, due to its location in relation to the [[Big Dipper]] (aka the Plough) [[Asterism (astronomy)|asterism]] of [[Ursa Major]]. While it is well known that the two outer stars of the 'dipper' point to the modern-day [[pole star]] [[Polaris]], it is less well known that the two inner stars, [[Phecda]] and [[Megrez]], point to Thuban, just 15 degrees of arc from Megrez. Thuban is not bright enough to be viewed from badly [[light pollution|light-polluted]] areas.


=== Pole star ===
=== Pole star ===
[[File:Precession N.gif|thumb|left|Precession of the equinoxes for the Pole Star. Thuban is toward the right of the image, below the -2000 mark.]]
[[File:Precession N.gif|thumb|left|Precession of the equinoxes for the Pole Star. Thuban is toward the right of the image, below the −2000 mark.]]
Due to the [[Precession (astronomy)|precession]] of [[Earth]]'s rotational axis, Thuban was the naked-eye star closest to the [[north pole]] from 3942 BC, when it superseded [[Tau Herculis]] as the pole star, until 1793 BC, when it was superseded by [[Kappa Draconis]]. It was closest to the pole in 2830 BC, when it was less than ten [[arcminutes]] away from the pole.<ref name="MOORE">{{Cite book|doi=10.1007/978-1-4471-3613-2|title=The Observer's Year|year=1998|last1=Moore|first1=Patrick|isbn=978-3-540-76147-1|url-access=registration|url=https://archive.org/details/observersyear36600moor}}</ref> It remained within one degree of celestial north for nearly 200 years afterwards, and even 900 years after its closest approach, was just five degrees off the pole. Thuban was considered the pole star until about 1800 BC, when the much brighter [[Beta Ursae Minoris]] (Kochab) began to approach the pole as well.
Due to the [[Precession (astronomy)|precession]] of [[Earth]]'s rotational axis, Thuban was the naked-eye star closest to the [[north pole]] from 3942&nbsp;BC, when it superseded [[Tau Herculis]] as the pole star, until 1793&nbsp;BC, when it was superseded by [[Kappa Draconis]]. It was closest to the pole in 2830&nbsp;BC, when it was less than 10&nbsp;[[arcminutes]] away from the pole.<ref name="MOORE">{{Cite book |doi=10.1007/978-1-4471-3613-2 |title=The Observer's Year |year=1998 |last1=Moore |first1=Patrick |isbn=978-3-540-76147-1 |url-access=registration |url=https://archive.org/details/observersyear36600moor}}</ref> It remained within one degree of celestial north for nearly 200 years afterwards, and even 900 years after its closest approach, was just 5° off the pole. Thuban was considered the pole star until about 1800&nbsp;BC, when the much brighter [[Beta Ursae Minoris]] (Kochab) began to approach the pole as well.


Having gradually drifted away from the pole over the last 4,800 years, Thuban is now seen in the night sky at a [[declination]] of 64° 20' 45.6", [[Right ascension|RA]] 14h 04m 33.58s. After moving nearly 47 degrees off the pole by [[List of future astronomical events#After 10,000 AD|10,000 AD]], Thuban will gradually move back toward the north celestial pole. In [[List of future astronomical events#After 10,000 AD|20,346 AD]], it will again be the pole star, that year reaching a maximum declination of {{DEC|88|43|17.3}}, at right ascension {{RA|19|08|54.17}}.{{citation needed|date=July 2015}}
Having gradually drifted away from the pole over the last 4800 years, Thuban is now seen in the night sky at a [[declination]] of {{DEC|64|20|45.6}}, [[Right ascension|RA]] {{RA|14|04|33.58}}. After moving nearly 47° off the pole by [[List of future astronomical events#After 10,000 AD|10,000&nbsp;AD]], Thuban will gradually move back toward the north celestial pole. In [[List of future astronomical events#After 10,000 AD|20,346&nbsp;AD]], it will again be the pole star, that year reaching a maximum declination of {{DEC|88|43|17.3}}, at right ascension {{RA|19|08|54.17}}.{{citation needed|date=July 2015}}


{| class="wikitable" style="margin: 1em auto 1em auto;"
{| class="wikitable" style="margin: 1em auto 1em auto; text-align:center;"
! width="120" align="center"|Preceded by
! Preceded by
! width="160" align="center"|[[Pole star]]
! [[Pole star]]
! width="120" align="center"|Succeeded by
! Succeeded by
|-
|-
|align="center"|[[Tau Herculis]]
| [[Tau Herculis]]
| c. 3900–1800 BC
|align="center"|3942–1793 BC
|align="center"|[[Kochab]]
| [[Kochab]]
|}
|}


==Binary system==
==Binary system==
[[File:AlphaDraLightCurve.png|thumb|left|A [[light curve]] for Thuban, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data.<ref name=MAST>{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=16 October 2022}}</ref> The main plot shows the entire light curve, and the inset plots show the primary and secondary minima with an expanded scale.]]
Thuban is a single-lined [[spectroscopic binary]]. Only the primary star can be detected in the [[stellar spectrum|spectrum]]. The radial velocity variations of the primary can be measured and the pair have a somewhat eccentric orbit of 51.4 days. Making some assumptions based on the faintness of the secondary, the stars are likely to be about 0.46 [[astronomical unit]] apart and the secondary is a little less massive than the primary.<ref name=kallinger/> The secondary is likely to be a [[main-sequence star]] slightly cooler than the primary, possibly an A2 spectral class.<ref name=behr/>
Thuban is a single-lined [[spectroscopic binary]]. For a long time, only the primary star could be detected in the [[stellar spectrum|spectrum]]. The radial velocity variations of the stars can be measured and the pair have a somewhat eccentric orbit of 51.4 days.<ref name=Pavlovski/> The secondary is a [[main-sequence star]] slightly cooler than the primary, with an A1 spectral class.<ref name=Pavlovski/>


The secondary star was detected in high spatial resolution observations using the [[Navy Precision Optical Interferometer]]. The secondary star is 1.8 magnitudes (at 700 [[Nanometre|nm]]) fainter than the primary star and was detected at separations ranging from 6.2 to 2.6 [[milliarcseconds]].<ref>{{Cite journal|last1=Hutter|first1=D. J.|last2=Zavala|first2=R. T.|last3=Tycner|first3=C.|last4=Benson|first4=J. A.|last5=Hummel|first5=C. A.|last6=Sanborn|first6=J.|last7=Franz|first7=O. G.|last8=Johnston|first8=K. J.|date=2016-11-01|title=Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F-K|journal=The Astrophysical Journal Supplement Series|volume=227|issue=1|pages=4|doi=10.3847/0067-0049/227/1/4|issn=0067-0049|bibcode=2016ApJS..227....4H|arxiv = 1609.05254 |s2cid=118803592}}</ref> Eclipses were detected using data obtained with the [[Transiting Exoplanet Survey Satellite]] (TESS).<ref>{{Cite journal|last1=Bedding|first1=Timothy R.|last2=Hey|first2=Daniel R.|last3=Murphy|first3=Simon J.|date=2019-10-31|title=A Dance with Dragons: TESS Reveals α Draconis is a Detached Eclipsing Binary|journal=Research Notes of the AAS|language=en|volume=3|issue=10|pages=163|doi=10.3847/2515-5172/ab5112|arxiv=1910.12449|bibcode=2019RNAAS...3..163B|issn=2515-5172}}</ref> The presence of eclipses places Thuban into the class of binaries known as [[eclipsing binaries]].
The secondary star was detected in high spatial resolution observations using the [[Navy Precision Optical Interferometer]]. The secondary star is 1.8 magnitudes (at 700 [[Nanometre|nm]]) fainter than the primary star and was detected at separations ranging from 6.2 to 2.6 [[milliarcseconds]].<ref>{{Cite journal|last1=Hutter|first1=D. J.|last2=Zavala|first2=R. T.|last3=Tycner|first3=C.|last4=Benson|first4=J. A.|last5=Hummel|first5=C. A.|last6=Sanborn|first6=J.|last7=Franz|first7=O. G.|last8=Johnston|first8=K. J.|date=2016-11-01|title=Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F-K|journal=The Astrophysical Journal Supplement Series|volume=227|issue=1|pages=4|doi=10.3847/0067-0049/227/1/4|issn=0067-0049|bibcode=2016ApJS..227....4H|arxiv = 1609.05254 |s2cid=118803592 |doi-access=free }}</ref> Eclipses were detected using data obtained with the [[Transiting Exoplanet Survey Satellite]] (TESS).<ref>{{Cite journal|last1=Bedding|first1=Timothy R.|last2=Hey|first2=Daniel R.|last3=Murphy|first3=Simon J.|date=2019-10-31|title=A Dance with Dragons: TESS Reveals α Draconis is a Detached Eclipsing Binary|journal=Research Notes of the AAS|language=en|volume=3|issue=10|pages=163|doi=10.3847/2515-5172/ab5112|arxiv=1910.12449|bibcode=2019RNAAS...3..163B|s2cid=213224065 |issn=2515-5172 |doi-access=free }}</ref> The presence of eclipses places Thuban into the class of binaries known as [[eclipsing binaries]].<ref name=Pavlovski/>


== Properties ==
== Properties ==
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Thuban is not a main-sequence star; it has now ceased [[hydrogen]] [[nuclear fusion|fusion]] in its core. That makes it a white [[giant star]], being 120 times more [[Solar luminosity|luminous than the Sun]]. It is 300 light-years away and its brightness is only decreased by 0.003 of a magnitude by intervening gas and dust.<ref name=murphy/>
Thuban is not a main-sequence star; it has now ceased [[hydrogen]] [[nuclear fusion|fusion]] in its core. That makes it a white [[giant star]], being 120 times more [[Solar luminosity|luminous than the Sun]]. It is 300 light-years away and its brightness is only decreased by 0.003 of a magnitude by intervening gas and dust.<ref name=murphy/>

==Popular culture==
The [[United States Navy]] ship {{USS|Thuban|AKA-19}} was built in 1943 and decommissioned in 1967.

Thuban has featured in multiple [[Stars and planetary systems in fiction#Alpha Draconis (Thuban)|works of fiction]].


==References==
==References==
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{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}
{{Authority control}}
{{Authority control}}
{{Pole star}}

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{{DEFAULTSORT:Thuban}}
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[[Category:Henry Draper Catalogue objects|123299]]
[[Category:Henry Draper Catalogue objects|123299]]
[[Category:Hipparcos objects|068756]]
[[Category:Hipparcos objects|068756]]
[[Category:HR objects|5291]]
[[Category:Bright Star Catalogue objects|5291]]
[[Category:Northern pole stars]]
[[Category:Northern pole stars]]
[[Category:Stars with proper names]]

Latest revision as of 19:04, 26 October 2024

This article is about the star. For AMD's Thuban processor core, see Phenom II.
Thuban
Location of Thuban (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 14h 04m 23.3500s[1]
Declination 64° 22′ 33.062″[1]
Apparent magnitude (V) 3.67[2]
Characteristics
Spectral type A0IV + A1V[3]
U−B color index −0.08
B−V color index −0.049±0.005[2]
Variable type suspected Maia[4]
Astrometry
Radial velocity (Rv)−13.0 km/s
Proper motion (μ) RA: −56.34[1] mas/yr
Dec.: 17.21[1] mas/yr
Parallax (π)10.76 ± 0.17 mas[1]
Distance303 ± 5 ly
(93 ± 1 pc)
Absolute magnitude (MV)−1.20[5]
Orbit[3]
Period (P)51.417350 d
Semi-major axis (a)5.52 mas
Eccentricity (e)0.43
Inclination (i)85.4°
Longitude of the node (Ω)252.6°
Periastron epoch (T)JD 2453498.8
Argument of periastron (ω)
(secondary)		22.4°
Semi-amplitude (K1)
(primary)		48.512 km/s
Semi-amplitude (K2)
(secondary)		63.58 km/s
Details[3]
α Draconis A
Alpha Draconis A
Mass3.186 M☉
Radius4.932 R☉
Luminosity240 L☉
Surface gravity (log g)3.555 cgs
Temperature10225 K
Rotational velocity (v sin i)25.4 km/s
Age280 Myr
α Draconis B
Alpha Draconis B
Mass2.431 M☉
Radius2.326 R☉
Luminosity47.5 L☉
Surface gravity (log g)4.090 cgs
Temperature9930 K
Rotational velocity (v sin i)168 km/s
Age345 Myr
Other designations
Alpha Dra, α Dra, 11 Dra, AG+64° 666, BD+65° 978, FK5 521, GC 19019, HD 123299, HIP 68756, HR 5291, SAO 16273, PPM 18861, PLX 3209, TYC 4174-1262-1, GSC 04174-01262, IRAS 14030+6436, 2MASS J14042335+6422331
Database references
SIMBADdata

Thuban (/ˈθjuːbæn/),[6] with Bayer designation Alpha Draconis or α Draconis, is a binary star system in the northern constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star from the 4th to 2nd millennium BC.

Johann Bayer gave Thuban the designation Alpha and placed it as the only member of his secundae magnitude class in Draco, although its current apparent magnitude of 3.65 means it is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis (Eltanin), which Bayer placed in his tertiae magnitude class although its current apparent magnitude is 2.24.[7]

Nomenclature

[edit]

α Draconis (Latinised to Alpha Draconis) is the star's Bayer designation.

The traditional name Thuban is derived from the Arabic word ثعبان thuʿbān ('large snake' (e.g. a python or a legendary draconian serpent)). It is sometimes known as the Dragon's Tail and as Adib /əˈdiːb/.[6] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[8] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[9] included a table of the first two batches of names approved by the WGSN; which included Thuban for this star. It is now so entered in the IAU Catalog of Star Names.[10]

In Chinese, 紫微右垣 (Zǐ Wēi Yòu Yuán), meaning Right Wall of Purple Forbidden Enclosure, refers to an asterism consisting of Alpha Draconis, Kappa Draconis, Lambda Draconis, 24 Ursae Majoris, 43 Camelopardalis, Alpha Camelopardalis and BK Camelopardalis.[11] Consequently, the Chinese name for Alpha Draconis itself is 紫微右垣一 (Zǐ Wēi Yòu Yuán yī, English: the First Star of Right Wall of Purple Forbidden Enclosure),[12] representing 右樞 (Yòushū), meaning Right Pivot.[13]

Visibility

[edit]

Given good viewing conditions, Thuban is relatively easy to spot in the night sky, due to its location in relation to the Big Dipper (aka the Plough) asterism of Ursa Major. While it is well known that the two outer stars of the 'dipper' point to the modern-day pole star Polaris, it is less well known that the two inner stars, Phecda and Megrez, point to Thuban, just 15 degrees of arc from Megrez. Thuban is not bright enough to be viewed from badly light-polluted areas.

Pole star

[edit]
Precession of the equinoxes for the Pole Star. Thuban is toward the right of the image, below the −2000 mark.

Due to the precession of Earth's rotational axis, Thuban was the naked-eye star closest to the north pole from 3942 BC, when it superseded Tau Herculis as the pole star, until 1793 BC, when it was superseded by Kappa Draconis. It was closest to the pole in 2830 BC, when it was less than 10 arcminutes away from the pole.[14] It remained within one degree of celestial north for nearly 200 years afterwards, and even 900 years after its closest approach, was just 5° off the pole. Thuban was considered the pole star until about 1800 BC, when the much brighter Beta Ursae Minoris (Kochab) began to approach the pole as well.

Having gradually drifted away from the pole over the last 4800 years, Thuban is now seen in the night sky at a declination of 64° 20′ 45.6″, RA 14h 04m 33.58s. After moving nearly 47° off the pole by 10,000 AD, Thuban will gradually move back toward the north celestial pole. In 20,346 AD, it will again be the pole star, that year reaching a maximum declination of 88° 43′ 17.3″, at right ascension 19h 08m 54.17s.[citation needed]

Preceded by Pole star Succeeded by
Tau Herculis c. 3900–1800 BC Kochab

Binary system

[edit]
A light curve for Thuban, plotted from TESS data.[15] The main plot shows the entire light curve, and the inset plots show the primary and secondary minima with an expanded scale.

Thuban is a single-lined spectroscopic binary. For a long time, only the primary star could be detected in the spectrum. The radial velocity variations of the stars can be measured and the pair have a somewhat eccentric orbit of 51.4 days.[3] The secondary is a main-sequence star slightly cooler than the primary, with an A1 spectral class.[3]

The secondary star was detected in high spatial resolution observations using the Navy Precision Optical Interferometer. The secondary star is 1.8 magnitudes (at 700 nm) fainter than the primary star and was detected at separations ranging from 6.2 to 2.6 milliarcseconds.[16] Eclipses were detected using data obtained with the Transiting Exoplanet Survey Satellite (TESS).[17] The presence of eclipses places Thuban into the class of binaries known as eclipsing binaries.[3]

Properties

[edit]
Thuban (α Dra) in optical light

Thuban has a spectral class of A0III, indicating its similarity to Vega in temperature and spectrum, but more luminous and more massive. It has been used as an MK spectral standard for the A0III type.[18]

Thuban is not a main-sequence star; it has now ceased hydrogen fusion in its core. That makes it a white giant star, being 120 times more luminous than the Sun. It is 300 light-years away and its brightness is only decreased by 0.003 of a magnitude by intervening gas and dust.[5]

References

[edit]
  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. ^ a b Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. ^ a b c d e f Pavlovski, K.; Hummel, C. A.; Tkachenko, A.; Dervişoğlu, A.; Kayhan, C.; Zavala, R. T.; Hutter, D. J.; Tycner, C.; Şahin, T.; Audenaert, J.; Baeyens, R.; Bodensteiner, J.; Bowman, D. M.; Gebruers, S.; Jannsen, N. E.; Mombarg, J. S. G. (2022). "Dynamical parallax, physical parameters, and evolutionary status of the components of the bright eclipsing binary α Draconis". Astronomy & Astrophysics. 658: A92. arXiv:2111.03887. Bibcode:2022A&A...658A..92P. doi:10.1051/0004-6361/202142292. S2CID 243847585.
  4. ^ Kallinger, T.; Iliev, I.; Lehmann, H.; Weiss, W. W. (2005). "The puzzling Maia candidate star α Draconis". Proceedings of the International Astronomical Union. 2004: 848–852. Bibcode:2004IAUS..224..848K. doi:10.1017/S1743921305009865.
  5. ^ a b Murphy, Simon J.; Paunzen, Ernst (2017). "Gaia's view of the λ Boo star puzzle". Monthly Notices of the Royal Astronomical Society. 466 (1): 546. arXiv:1612.01528. Bibcode:2017MNRAS.466..546M. doi:10.1093/mnras/stw3141. S2CID 119328659.
  6. ^ a b 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.
  7. ^ Johann Bayer (1603). Uranometria: Omnivm Asterismorvm Continens Schemata, Nova Methodo Delineata, Aereis Laminis Expressa.
  8. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  9. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  10. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  11. ^ (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.
  12. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-19 at the Wayback Machine, Hong Kong Space Museum. Retrieved 2010-11-23.
  13. ^ (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived 2010-08-10 at the Wayback Machine, Hong Kong Space Museum. Retrieved 2010-11-23.
  14. ^ Moore, Patrick (1998). The Observer's Year. doi:10.1007/978-1-4471-3613-2. ISBN 978-3-540-76147-1.
  15. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 16 October 2022.
  16. ^ Hutter, D. J.; Zavala, R. T.; Tycner, C.; Benson, J. A.; Hummel, C. A.; Sanborn, J.; Franz, O. G.; Johnston, K. J. (2016-11-01). "Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F-K". The Astrophysical Journal Supplement Series. 227 (1): 4. arXiv:1609.05254. Bibcode:2016ApJS..227....4H. doi:10.3847/0067-0049/227/1/4. ISSN 0067-0049. S2CID 118803592.
  17. ^ Bedding, Timothy R.; Hey, Daniel R.; Murphy, Simon J. (2019-10-31). "A Dance with Dragons: TESS Reveals α Draconis is a Detached Eclipsing Binary". Research Notes of the AAS. 3 (10): 163. arXiv:1910.12449. Bibcode:2019RNAAS...3..163B. doi:10.3847/2515-5172/ab5112. ISSN 2515-5172. S2CID 213224065.
  18. ^ Morgan, W. W.; Abt, Helmut A.; Tapscott, J. W. (1978). "Revised MK Spectral Atlas for stars earlier than the sun". Williams Bay: Yerkes Observatory. Bibcode:1978rmsa.book.....M.
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