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en>Rjwilmsi: Journal cites, added 1 DOI using AWB (9904)

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{{Starbox begin
| name = Alpha Herculis
}}
{{Starbox image
| image = [[File:Hercules Historical View.png|250px]]
| caption = Historical view of the [[Hercules (constellation)|Hercules]] constellation showing Rasalgethi as the '''α''' star and "Head of the Kneeler"
}}
{{Starbox observe
| epoch = J2000
| ra = {{RA|17|14|38.80}}<ref name=aaa323_L49/><ref name="LEEUWEN"/><ref name="SIMBAD"/>
| dec = {{DEC| +14|23|25.0}}<ref name=aaa323_L49/><ref name="LEEUWEN"/><ref name="SIMBAD"/>
| appmag_v = 2.9137 / 5.4<ref name=aaa323_L49/><ref name="LEEUWEN"/>
| constell = [[Hercules (constellation)|Hercules]]
}}
{{Starbox character
| class = M5IIvar / (G5III+F2V)
| b-v = 1.45<ref name="JOHNSON"/>
| u-b = 1.01<ref name="JOHNSON"/>
| variable = Semiregular
}}
{{Starbox astrometry
| prop_mo_ra = -6.71<ref name=aaa323_L49/><ref name="LEEUWEN"/><ref name="SIMBAD"/>
| prop_mo_dec = 32.78<ref name=aaa323_L49/><ref name="LEEUWEN"/><ref name="SIMBAD"/>
| parallax = 9.07
| p_error = 1.32
| parallax_footnote = <ref name=aaa323_L49/><ref name="LEEUWEN"/>
|absmag_v = -2.30
}}
{{Starbox detail
| mass = {{nowrap|2.15 ± 0.22}}<ref name=aaa465_2_593/>
| radius = 387<ref name=aaa465_2_593/>
| luminosity = 8,300<ref name=aaa465_2_593/>
| temperature = 2,800<ref name=aaa465_2_593/>
| metal =
| gravity = {{nowrap|−0.41 ± 0.19}}<ref name=aaa465_2_593/>
| rotational_velocity =
| age =
}}
{{Starbox catalog
|names=Ras Algethi, Rasalgethi, [[Bayer designation|α Her]], [[Flamsteed designation|64 Her]], [[Harvard Revised catalogue|HR]] 6406, [[Bonner Durchmusterung|BD]] +14° 3207, [[Henry Draper Catalogue|HD]] 156014J, [[Hipparcos catalogue|HIP]] 84345, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 102680, [[Catalog of Components of Double and Multiple Stars|CCDM]] J17146+1424AB, [[American Association of Variable Star Observers|AAVSO]] 1710+14
}}
{{Starbox reference
| Simbad=HD+156014J
}}
{{Starbox end}}
'''Alpha Herculis''' (α Her, α Herculis) is a multiple [[star system]] in the [[constellation]] [[Hercules (constellation)|Hercules]]. It has the traditional name '''Rasalgethi''' or '''Ras Algethi''' ({{lang-ar|رأس الجاثي ra's al-jaθiyy}} ''Head of the Kneeler''), and the [[Flamsteed designation]] '''64 Herculis'''.<ref name="BBC1">{{cite web
|title=Constellations: Hercules 'the Strongman'
|publisher=The BBC (British Broadcasting Corporation)
|author=Kurt Vonnegut
|url=http://www.bbc.co.uk/dna/h2g2/A29778916
|accessdate=2010-11-14}}</ref> The traditional name "Head" comes from the fact that in antiquity Hercules was depicted upside down on the constellation maps.

The term ''ra's al-jaθiyy'' or '''Ras al Djathi''' was appeared in the catalogue of stars in the ''Calendarium'' of [[Al Achsasi al Mouakket]], which was translated into [[Latin]] as '''Caput Ingeniculi'''.<ref>{{cite journal
| last=Knobel | first=E. B.
| title=Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket
| journal=Monthly Notices of the Royal Astronomical Society
| volume=55 | page=429 |date=June 1895
| bibcode=1895MNRAS..55..429K }}</ref>

In [[Chinese astronomy]], Rasalgethi is called 帝座, [[Pinyin]]: Dìzuò, meaning '' Emperor's Seat'', because this star is marking itself and stand alone in ''Emperor's Seat'' asterism, [[Heavenly Market enclosure]] (see : [[Chinese constellation]]).<ref>{{zh icon}} [http://aeea.nmns.edu.tw/2006/0606/ap060625.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 25 日]</ref> 帝座 (Dìzuò) was westernized into '''Ti Tso''' by R.H. Allen, with the same meaning <ref>[http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Hercules*.html Richard Hinckley Allen: Star Names — Their Lore and Meaning: Hercules]</ref>

== Properties ==
The angular diameter of the red giant, α1 Her, has been measured with an [[interferometer]] as
34 ± 0.8 [[arcsecond|mas]], or 0.034 arcseconds.<ref name="BENSON">{{cite journal
| author=Benson, J. A.; Dyck, H. M.; Mason, W. L.; Howell, R. R.; Ridgway, S. T.; Dixon, D. J.
| title=The infrared angular diameter of Alpha Herculis measured with a Michelson interferometer
| journal=Astronomical Journal
|date=December 1991
| volume=102
| pages=2091–2097
| doi= 10.1086/116033
| bibcode=1991AJ....102.2091B }}</ref> At an estimated distance of 110 [[parsec]]s from [[Hipparcos]],<ref name=aaa323_L49/><ref name="LEEUWEN"/><ref name=GSM/> this corresponds to a radius of about 280 million kilometers (or 170 million miles), which is roughly 400[[Solar radius|R☉]] or 1.87 [[astronomical unit|AU]].<ref name="NOTERADIUS" group="note">To determine the Rasalgheti's radius in terms of solar units, the calculations begin with the formula for [[angular diameter]] as follows:

:<math>\begin{smallmatrix} {\delta} = \frac{d_R}{D_R}\end{smallmatrix}</math>

where '''''δ''''' equals Rasalgheti's angular diameter in [[arcseconds]], '''''dR''''' the star's '''d'''iameter in [[Astronomical Unit|AU]], and '''''DR''''' the '''D'''istance from Earth in parsecs. If we know the angular diameter and the Distance, then we can solve for '''''dR''''' as follows:

:<math>\begin{smallmatrix}d_R = \delta \cdot D_R = {0.034} \cdot 110.0 = 3.740 AU \end{smallmatrix}</math>.

To obtain Rasalgheti's radius:

:<math>\begin{smallmatrix}R_R = {\left ( {\frac {d_R}{2}} \right )} = {\left ( {\frac {3.740}{2}} \right )} = 1.870 AU \end{smallmatrix}</math>.
Converting into Solar units, 1 [[Astronomical Unit|AU]] = 149,597,871 km and the mean radius of the [[Sun]] = 696,000 km, hence the calculation:

:<math>\begin{smallmatrix}d_B = {\left ( 1.87 AU \right )} {\left ( {\frac {149,597,871 km}{696,000 km}} \right )} = 280,000,000 km = 402 R_{\odot} \end{smallmatrix}</math> (rounded).</ref> If Rasalgheti were at the center of our [[Solar System]] its radius would extend past the orbit of [[Mars]] at 1.5 [[astronomical unit|AU]] but not quite as far as the [[asteroid belt]]. The red giant is estimated to have started its life with about 7-8 [[solar mass]]es.<ref name="KALER"/> Like most [[Stellar classification#Class M|type M]] stars near the end of their lives, Rasalgethi is experiencing a high degree of [[stellar mass loss]] creating a sparse, gaseous envelope that extends at least 90 [[astronomical unit]]s.<ref>{{cite journal
| last=Deutsch
| first=Armin J.
| title=The Circumstellar Envelope of Alpha Herculis
| journal=Astrophysical Journal
|date=March 1956
| volume=123
| pages=210–227
| doi=10.1086/146152
| bibcode=1956ApJ...123..210D}}</ref>

== Star system ==
When viewed through a telescope, this system is resolved into two components designated α1 and α2. These two components are more than 500 [[astronomical units]] apart, with an estimated orbital period of approximately 3600 years. α1 is a relatively massive red [[bright giant]]. α2 is actually a [[double star]] system with a primary yellow giant star and a secondary, yellow-white dwarf star. (These components are sometimes designated α Herculis A, Ba and Bb, respectively.)

==See also==
*[[List of largest known stars]]
*[[Lists of stars]] in the constellation [[List of stars in Hercules|Hercules]]
*[[Betelgeuse#Circumstellar dynamics|Betelgeuse mass loss]]
*[[Stellar classification#Spectral types|Spectral types F, G & M]]

== Notes ==
<references group="note" />

== References ==
{{reflist|refs=

<ref name=aaa465_2_593>{{citation | last1=Schröder | first1=K.-P. | last2=Cuntz | first2=M. | title=A critical test of empirical mass loss formulas applied to individual giants and supergiants | journal=Astronomy and Astrophysics | volume=465 | issue=2 | pages=593–601 |date=April 2007 | doi=10.1051/0004-6361:20066633 | bibcode=2007A&A...465..593S |arxiv = astro-ph/0702172 }}</ref>

<ref name="KALER">{{cite web | title=RASALGETHI (Alpha Herculis) | publisher=University of Illinois | first1=James B. | last1=Kaler | url=http://stars.astro.illinois.edu/sow/rasalgethi.html | accessdate=2007-03-07 }}</ref>

<ref name="JOHNSON">{{cite journal | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewski | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Comm. Lunar Plan. Lab. | volume=4 | pages=99 | year=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name="SIMBAD">{{cite web | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=alpha+her&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id | title =SIMBAD query result:NAME RASALGETHI -- Semi-regular pulsating Star | publisher =Centre de Données astronomiques de Strasbourg | accessdate = 2010-09-26 }}</ref>

<ref name=aaa323_L49>{{citation | last1=Perryman | first1=M. A. C. | last2=Lindegren | first2=L. | last3=Kovalevsky | first3=J. | last4=et al. | title=The Hipparcos Catalogue | journal=Astronomy and Astrophysics | volume=323 |date=July 1997 | pages=L49–L52 | bibcode=1997A&A...323L..49P}}</ref>

<ref name="LEEUWEN">{{cite journal | title=Hipparcos, the New Reduction | last1=van Leeuwen | first1=F |date=November 2007 | publisher=[[Centre de Données astronomiques de Strasbourg]] | pages=653 | issue=2 | volume=474 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V |arxiv = 0708.1752 }}</ref>

<ref name=GSM>{{citation | last=Perryman | first=Michael | title=The Making of History's Greatest Star Map | location=Heidelberg | publisher=Springer-Verlag | year=2010 | doi=10.1007/978-3-642-11602-5}}</ref>

}}

==External links==
*An Atlas of the Universe: [http://www.atlasoftheuniverse.com/orbits.html Multiple Star Orbits]
*Upside down Hercules showing Rasalgethi as the head: [http://www.ne.jp/asahi/stellar/scenes/seiza_e/her.htm Hercules]

{{Sky|17|14|38.858|+|14|23|25.20|1000000}}
{{Stars of Hercules}}

[[Category:Double stars]]
[[Category:Hercules (constellation)]]
[[Category:Bayer objects|Herculis, Alpha]]
[[Category:Flamsteed objects|Herculis, 64]]
[[Category:Triple star systems]]
[[Category:Stars with proper names]]
[[Category:M-type bright giants]]
[[Category:G-type giants]]
[[Category:F-type main-sequence stars]]
[[Category:Objects within 1000 ly of Earth]]

Tensegrity - Revision history

en>Monkbot: /* Bibliography */Task 6h: add |script-title=; replace {{xx icon}} with |language= in CS1 citations; clean up language icons;

en>Rjwilmsi: Journal cites, added 1 DOI using AWB (9904)