View source for Hercules (constellation)

{{Short description|Constellation in the northern celestial hemisphere}}
{{Infobox constellation
| name = Hercules
| abbreviation = Her
| genitive = Herculis<ref name=thompson2/>
| pronounce = {{IPAc-en|ˈ|h|ɜːr|k|j|ʊ|l|iː|z}},<br />genitive {{IPAc-en|ˈ|h|ɜːr|k|j|ʊ|l|ɪ|s}} |
| symbolism = [[Heracles]]
| RA = {{RA|17}}
| dec= {{DEC|+30}}
| family = [[Hercules Family|Hercules]]
| quadrant = NQ3
| areatotal = 1225
| arearank = 5th
| numbermainstars = 14, 22
| numberbfstars = 102
| numberstarsplanets = 15
| numberbrightstars = 2
| numbernearbystars = 9
| brighteststarname = [[Beta Herculis|β Her]] (Kornephoros)
| starmagnitude = 2.78
| neareststarname = [[Gliese 661]]
| stardistancely = 20.62
| stardistancepc = 6.32
| numbermessierobjects = 2
| meteorshowers = [[Tau Herculids]]
| bordering = [[Draco (constellation)|Draco]]<br />[[Boötes]]<br />[[Corona Borealis]]<br />[[Serpens|Serpens Caput]]<br />[[Ophiuchus]]<br />[[Aquila (constellation)|Aquila]]<br />[[Sagitta]]<br />[[Vulpecula]]<br />[[Lyra]]<ref name=thompson2/>
| latmax = [[North Pole|90]]
| latmin = [[50th parallel south|50]]
| month = [[July]]
| notes =
}}

'''Hercules''' is a [[constellation]] named after [[Hercules]], the [[Roman mythology]] hero adapted from the [[Greek mythology|Greek]] hero [[Heracles]]. Hercules was one of the 48 constellations listed by the second-century [[astronomer]] [[Ptolemy]], and it remains one of the [[IAU designated constellations|88 modern constellations]] today. It is the fifth-largest of the modern constellations and is the largest of [[List of brightest stars|the 50]] which have no stars brighter than apparent [[Magnitude (astronomy)|magnitude]] +2.5.

==Characteristics==
[[File:HerculesCC.jpg|thumb|left|200px|The constellation Hercules as it may appear to the [[naked eye]].]]
Hercules is bordered by [[Draco (constellation)|Draco]] to the north; [[Boötes]], [[Corona Borealis]], and [[Serpens|Serpens Caput]] to the west; [[Ophiuchus]] to the south; [[Aquila (constellation)|Aquila]] to the southwest; and [[Sagitta]], [[Vulpecula]], and [[Lyra]] to the east. Covering 1225.1&nbsp;square degrees and 2.970% of the night sky, it ranks fifth among the 88 constellations in size.<ref name=tirionconst>{{cite web |url=http://www.ianridpath.com/constellations1.html |title=Constellations: Andromeda–Indus |work=Star Tales |last1=Ridpath |first1=Ian |author-link=Ian Ridpath |access-date=2016-09-12}}</ref> The three-letter abbreviation for the constellation, as adopted by the [[International Astronomical Union]] in 1922, is 'Her'.<ref name="pa30_469">{{cite magazine |last=Russell |first=Henry Norris |author-link=Henry Norris Russell |title=The New International Symbols for the Constellations |magazine=[[Popular Astronomy (US magazine)|Popular Astronomy]] |volume=30 |page=469 |bibcode=1922PA.....30..469R |date=1922}}</ref> The official constellation boundaries, as set by [[Eugène Joseph Delporte|Eugène Delporte]] in 1930, are defined by a polygon of 32 segments (''illustrated in infobox''). In the [[equatorial coordinate system]], epoch 2000, the [[right ascension]] coordinates of these borders lie between {{RA|16|00|26.64}} and {{RA|18|57|49.50}}, while the [[declination]] coordinates are between +3.67° and +51.32°.<ref name="boundary">{{cite journal |title=Hercules, Constellation Boundary |journal=The Constellations |publisher=[[International Astronomical Union]] |url=https://www.iau.org/public/themes/constellations/#her |access-date=2016-09-12}}</ref> In mid-northern latitudes, Hercules is best observed from mid-spring until early autumn, [[culmination|culminating]] at midnight on June 13.<ref name=thompson2>{{cite book |title=Illustrated Guide to Astronomical Wonders: From Novice to Master Observer |last1=Thompson |first1=Robert Bruce |first2=Barbara |last2=Fritchman |year=2007 |url=https://books.google.com/books?id=ymt9nj_uPhwC&pg=PA256 |pages=256–63 |isbn=978-0-596-52685-6 |publisher=[[O'Reilly Media, Inc.]] |location=Sebastopol, California}}</ref>

The [[solar apex]] is the direction of the open motion with respect to the [[Local Standard of Rest]]. This is located within the constellation of Hercules, around coordinates right ascension {{RA|18|00}} and declination {{DEC|30|00}}.<ref>{{cite book |title=Fundamental Astronomy |chapter=The Milky Way |editor1-first=Hannu |editor1-last=Karttunen |editor2-first=Pekka |editor2-last=Kröger |editor3-first=Heikki |editor3-last=Oja |editor4-first=Markku |editor4-last=Poutanen |editor5-first=Karl J. |editor5-last=Donner |edition=3rd |publisher=[[Springer Science & Business Media]] |page=392 |year=2013 |isbn=978-3662032152 |chapter-url=https://books.google.com/books?id=IyjrCAAAQBAJ&pg=PA392}}</ref> The north pole of the [[supergalactic coordinate system]] is located within this constellation at right ascension {{RA|18|55|01}} and declination {{DEC|+15|42|32}}.<ref name=SGNP>{{cite encyclopedia |first1=David |last1=Darling |title=supergalactic plane |encyclopedia=Encyclopedia of Science |access-date=2016-09-12 |url=http://www.daviddarling.info/encyclopedia/S/supergalactic_plane.html}}</ref>

==Stars==

{{See also|List of stars in Hercules}}
Hercules has no [[apparent magnitude|first or second magnitude]] stars. However, it does have several stars above magnitude 4. [[Alpha Herculis]], traditionally called Rasalgethi, is a [[triple star]] system, partly resolvable in small amateur telescopes, 359 light-years from Earth. Its common name means "the kneeler's head".<ref>{{cite web|url=http://stars.astro.illinois.edu/sow/rasalgethi.html |title=Rasalgethi |last=Kaler |first=Jim |date=4 May 2007 |access-date=6 July 2019 |website=STARS, University of Illinois}}</ref> The primary is an irregular [[variable star]]; it is a [[bright giant]] with a minimum magnitude of 4 and a maximum magnitude of 3. It has a diameter of roughly 400 [[solar diameter]]s.<ref>{{citation
| title=The Age and Mass of the α Herculis Triple-star System from a MESA Grid of Rotating Stars with 1.3 <= M/M ⊙ <= 8.0
| last1=Moravveji | first1=Ehsan | last2=Guinan | first2=Edward F.
| last3=Khosroshahi | first3=Habib | last4=Wasatonic | first4=Rick
| journal=The Astronomical Journal | date=December 2013
| volume=146 | issue=6 | id=148 | pages=13
| doi=10.1088/0004-6256/146/6/148 | bibcode=2013AJ....146..148M
| arxiv=1308.1632 | s2cid=117872505 | postscript=.
}}</ref> The secondary, a [[spectroscopic binary]] that orbits the primary every 3600 years, is a blue-green hued star of magnitude 5.6. [[Beta Herculis]], also called Kornephoros, is the brightest star in Hercules. It is a [[yellow giant]] of magnitude 2.8, 148 light-years from Earth; kornephoros means club-bearer.<ref>{{cite web|url=http://stars.astro.illinois.edu/sow/kornephoros.html |title=Kornephoros |last=Kaler |first=Jim |access-date=6 July 2019 |website=STARS, University of Illinois}}</ref> [[Delta Herculis]] A is a double star divisible in small amateur telescopes. The primary is a blue-white star of magnitude 3.1, and is 78 light-years from Earth. The optical companion is of magnitude 8.2. [[Gamma Herculis]] is also a double star divisible in small amateur telescopes. The primary is a [[white giant]] of magnitude 3.8, 195 light-years from Earth. The optical companion, widely separated, is 10th magnitude. [[Zeta Herculis]] is a binary star that is becoming divisible in medium-aperture amateur telescopes, as the components widen to their peak in 2025. The system, 35 light-years from Earth, has a period of 34.5 years. The primary is a yellow-tinged star of magnitude 2.9 and the secondary is an orange star of magnitude 5.7.<ref name=rid>{{citation |title = Stars and Planets Guide |last1 = Ridpath |first1 = Ian |last2 = Tirion |first2 = Wil |date = 2001 |publisher = [[Princeton University Press]] |isbn = 0-691-08913-2|pages=154–156}}</ref>

Hercules hosts further quite bright double stars and binary stars. [[Kappa Herculis]] is a double star divisible in small amateur telescopes. The primary is a yellow giant of magnitude 5.0, 388 light-years from Earth; the secondary is an [[orange giant]] of magnitude 6.3, 470 light-years from Earth. [[Rho Herculis]] is a binary star 402 light-years from Earth, divisible in small amateur telescopes. Both components are blue-green giant stars; the primary is magnitude 4.5 and the secondary is magnitude 5.5. [[95 Herculis]] is a binary star divisible in small telescopes, 470 light-years from Earth. The primary is a silvery giant of magnitude 4.9, and the secondary is an old, reddish giant star of magnitude 5.2. The star HD164669 near the primary may be an optical double. [[100 Herculis]] is a double star easily divisible in small amateur telescopes. Both components are magnitude 5.8 blue-white stars; they are 165 and 230 light-years from Earth.<ref name=rid/>

There are several dimmer [[variable star]]s in Hercules. [[30 Herculis]], also called g Herculis, is a [[semiregular variable|semiregular]] [[red giant]] with a period of 3 months. 361 light-years from Earth, it has a minimum magnitude of 6.3 and a maximum magnitude of 4.3. [[68 Herculis]], also called u Herculis, is a [[Beta Lyrae variable|Beta Lyrae-type]] [[eclipsing binary]] star. 865 light-years from Earth, it has a period of 2 days; its minimum magnitude is 5.4 and its maximum magnitude is 4.7.<ref name=rid/>

[[Mu Herculis]] is 27.4 [[light-year]]s from Earth. The [[solar apex]], i.e., the point on the sky which marks the direction that the Sun is moving in its orbit around the center of the [[Milky Way]], narrowly figures in Hercules,<ref name=Struve>{{cite book |last1=Struve|first1=Otto |author-link=Otto Struve |last2=Lynds|first2=Beverly |last3=Pillans|first3=Helen | title=Elementary Astronomy | publisher=[[Oxford University Press]] | date=1959 | location=New York | pages=150 }}</ref> between Hercules' left elbow (near [[Omicron Herculis]]) and [[Vega]] (in neighboring [[Lyra]]).

==Planetary systems==

Fifteen stars in Hercules are known to be orbited by [[extrasolar planet]]s.
* [[14 Herculis]] has two planets. The planet [[14 Herculis b]] had the longest period (4.9 years)<ref>{{cite journal | display-authors=1 |first1=Robert A. | last1=Wittenmyer | last2=Endl | first2=Michael | last3=Cochran | first3=William D. | date=January 2007 | title=Long-Period Objects in the Extrasolar Planetary Systems 47 Ursae Majoris and 14 Herculis | journal=The Astrophysical Journal | volume=654 | issue=1 | pages=625–632 | arxiv=astro-ph/0609117 | bibcode=2007ApJ...654..625W | bibcode-access=free | doi=10.1086/509110 | doi-access=free | s2cid=14707902 }}</ref> and widest orbit (2.8 [[Astronomical unit|AU]]) at the time of discovery. The planet [[14 Herculis c]] orbits much further out with very low eccentricity. It was discovered in 2005 but was only confirmed in 2021.<ref>{{cite journal |bibcode=2006ApJ...645..688G |author=Goździewski, K. |author2=Konacki, M. |author3=Maciejewski, A. J.|title=Orbital Configurations and Dynamical Stability of Multiplanet Systems around Sun-like Stars HD 202206, 14 Herculis, HD 37124, and HD 108874|journal=[[The Astrophysical Journal]]|volume=645|issue=1|pages=688–703|date=2006|doi=10.1086/504030|arxiv = astro-ph/0511463 |s2cid=15012577 |url=http://authors.library.caltech.edu/5547/1/GOZapj06.pdf}}</ref><ref name=Rosenthal>{{citation|arxiv=2105.11583|year=2021|title=The California Legacy Survey. I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades|doi=10.3847/1538-4365/abe23c |last1=Rosenthal |first1=Lee J. |last2=Fulton |first2=Benjamin J. |last3=Hirsch |first3=Lea A. |last4=Isaacson |first4=Howard T. |last5=Howard |first5=Andrew W. |last6=Dedrick |first6=Cayla M. |last7=Sherstyuk |first7=Ilya A. |last8=Blunt |first8=Sarah C. |last9=Petigura |first9=Erik A. |last10=Knutson |first10=Heather A. |last11=Behmard |first11=Aida |last12=Chontos |first12=Ashley |last13=Crepp |first13=Justin R. |last14=Crossfield |first14=Ian J. M. |last15=Dalba |first15=Paul A. |last16=Fischer |first16=Debra A. |last17=Henry |first17=Gregory W. |last18=Kane |first18=Stephen R. |last19=Kosiarek |first19=Molly |last20=Marcy |first20=Geoffrey W. |last21=Rubenzahl |first21=Ryan A. |last22=Weiss |first22=Lauren M. |last23=Wright |first23=Jason T. |journal=The Astrophysical Journal Supplement Series |volume=255 |issue=1 |page=8 |bibcode=2021ApJS..255....8R |s2cid=235186973 |doi-access=free }}</ref>
* [[HD 149026]] has a [[transit (astronomy)|transiting]] [[hot Jupiter]] [[HD 149026 b|planet]].<ref>{{cite journal | title=The N2K Consortium. II. A Transiting Hot Saturn around HD 149026 with a Large Dense Core | last1=Sato | first1=Bun'ei | last2=Fischer | first2=Debra A. | last3=Henry | first3=Gregory W. | last4=Laughlin | first4=Greg | last5=Butler | first5=R. Paul | last6=Marcy | first6=Geoffrey W. | last7=Vogt | first7=Steven S. | last8=Bodenheimer | first8=Peter | last9=Ida | first9=Shigeru | last10=Toyota | first10=Eri | last11=Wolf | first11=Aaron | last12=Valenti | first12=Jeff A. | last13=Boyd | first13=Louis J. | last14=Johnson | first14=John A. | last15=Wright | first15=Jason T. | last16=Ammons | first16=Mark | last17=Robinson | first17=Sarah | last18=Strader | first18=Jay | last19=McCarthy | first19=Chris | last20=Tah | first20=K. L. | last21=Minniti | first21=Dante | display-authors=1 | journal=The Astrophysical Journal | volume=633 | issue=1 | pages=465–473 | year=2005 | arxiv=astro-ph/0507009 | bibcode=2005ApJ...633..465S | doi=10.1086/449306 | s2cid=629648 }}</ref>
* [[HD 154345]] has the planet [[HD 154345 b]], a long period (9.095 years) and wide orbit (4.18 AU).
* [[HD 164922]] has the first long period Saturn-like [[HD 164922 b|planet]] discovered. The [[mass]] is 0.36 M<sub>J</sub> and [[semimajor axis]] of 2.11 AU.<ref>{{cite journal | title=Catalog of Nearby Exoplanets | last1=Butler | first1=R. P. | last2=Wright | first2=J. T. | last3=Marcy | first3=G. W. | last4=Fischer | first4=D. A. | last5=Vogt | first5=S. S. | last6=Tinney | first6=C. G. | last7=Jones | first7=H. R. A. | last8=Carter | first8=B. D. | last9=Johnson | first9=J. A. | last10=McCarthy | first10=C. | last11=Penny | first11=A. J. | display-authors=1 | journal=The Astrophysical Journal | volume=646 | issue=1 | pages=505–522 | date=2006 | arxiv=astro-ph/0607493 | bibcode=2006ApJ...646..505B | doi=10.1086/504701 | s2cid=119067572 }}</ref> More planets have been discovered since.<ref>{{cite journal|arxiv=2005.03368|last1=Benatti|first1=S.|last2=Damasso|first2=M.|last3=Desidera|first3=S.|last4=Marzari|first4=F.|last5=Biazzo|first5=K.|last6=Claudi|first6=R.|last7=Di Mauro|first7=M. P.|last8=Lanza|first8=A. F.|last9=Pinamonti|first9=M.|last10=Barbato|first10=D.|last11=Malavolta|first11=L.|last12=Poretti|first12=E.|last13=Sozzetti|first13=A.|last14=Affer|first14=L.|last15=Bignamini|first15=A.|last16=Bonomo|first16=A. S.|last17=Borsa|first17=F.|last18=Brogi|first18=M.|last19=Bruno|first19=G.|last20=Carleo|first20=I.|last21=Cosentino|first21=R.|last22=Covino|first22=E.|last23=Frustagli|first23=G.|last24=Giacobbe|first24=P.|last25=Gonzalez|first25=M.|last26=Gratton|first26=R.|last27=Harutyunyan|first27=A.|last28=Knapic|first28=C.|last29=Leto|first29=G.|last30=Lodi|first30=M.|title=The GAPS programme at TNG|journal=Astronomy & Astrophysics|year=2020|volume=639|pages=A50|doi=10.1051/0004-6361/202037939|s2cid=218538033|display-authors=29}}</ref><ref name=Rosenthal />
* [[HD 147506]] has the most massive transiting planet [[HAT-P-2b]] at the time of discovery.<ref>{{cite journal | title=HD 147506b: A Supermassive Planet in an Eccentric Orbit Transiting a Bright Star | last1=Bakos | first1=G. Á. | last2=Kovács | first2=G | last3=Torres | first3=G. | last4=Fischer | first4=D. A. | last5=Latham | first5=D. W. | last6=Noyes | first6=R. W. | last7=Sasselov | first7=D. D. | last8=Mazeh | first8=T. | last9=Shporer | first9=A. | last10=Butler | first10=R. P. | last11=Stefanik | first11=R. P. | last12=Fernández | first12=J. M. | last13=Sozzetti | first13=A. | last14=Pál | first14=A. | last15=Johnson | first15=J. | last16=Marcy | first16=G. W. | last17=Winn | first17=J. N. | last18=Sipőcz | first18=B. | last19=Lázár | first19=J. | last20=Papp | first20=I. | last21=Sári | first21=P. | display-authors=1 | journal=The Astrophysical Journal | volume=670 | issue=1 | pages=826–832 | year=2007 | arxiv=0705.0126 | bibcode=2007ApJ...670..826B | bibcode-access=free | doi=10.1086/521866 | doi-access=free | s2cid=18286425 }}</ref> The mass is 8.65 M<sub>J</sub>.
* [[HD 155358]] has two planets around the lowest [[metallicity]] planet-harboring star (21% Sun). Both planets orbit in mild eccentricities.<ref>{{cite journal | url=http://www.iop.org/EJ/article/0004-637X/665/2/1407/71793.html | title=A Planetary System Around HD 155358: The Lowest Metallicity Planet Host Star | author=Cochran, W. | display-authors=etal | date=2007 | journal=The Astrophysical Journal | volume=665 | issue=2 | pages=1407–1412 | doi=10.1086/519555 | bibcode=2007ApJ...665.1407C|arxiv = 0705.3228 | s2cid=14591389 }}</ref>
* [[GSC 03089-00929]] has a short transiting planet [[TrES-3b]]. The [[orbital period|period]] was 31 hours.
* [[Gliese 649]] has a [[Gliese 649 b|saturnian planet]] around the red dwarf star.<ref>{{cite journal | title=The California Planet Survey II. A Saturn-Mass Planet Orbiting the M Dwarf Gl649 | last1=Johnson | first1=John Asher | last2=Howard | first2=Andrew W. | last3=Marcy | first3=Geoffrey W. | last4=Bowler | first4=Brendan P. | last5=Henry | first5=Gregory W. | last6=Fischer | first6=Debra A. | last7=Apps | first7=Kevin | last8=Isaacson | first8=Howard | last9=Wright | first9=Jason T. | display-authors=1 | journal=The Publications of the Astronomical Society of the Pacific | volume=122 | issue=888 | pages=149–155 | date=2010 | arxiv=0912.2730 | bibcode=2010PASP..122..149J | doi=10.1086/651007 | s2cid=119254409 }}</ref>
* [[HD 156668]] has an [[HD 156668 b|Earth mass planet]] with a minimum mass of four Earth masses.<ref>{{citation | display-authors=1 | last1=Howard | first1=Andrew W. | last2=Johnson | first2=John Asher | last3=Marcy | first3=Geoffrey W. | last4=Fischer | first4=Debra A. | last5=Wright | first5=Jason T. | last6=Henry | first6=Gregory W. | last7=Isaacson | first7=Howard | last8=Valenti | first8=Jeff A. | last9=Anderson | first9=Jay | last10=Piskunov | first10=Nikolai E. | title=The NASA-UC Eta-Earth Program. II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses | journal=The Astrophysical Journal | volume=726 | issue= 2 | page=73 |date=January 2011 | doi=10.1088/0004-637X/726/2/73 | bibcode=2011ApJ...726...73H |arxiv = 1003.3444 | s2cid=15559379 }}</ref>
* [[HD 164595]] is a G-type star with one known planet, [[HD 164595 b]].<ref>{{cite web
 | url=http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=HD+164595+b&type=CONFIRMED_PLANET| title=HD 164595 b Confirmed Planet Overview Page| website=[[NASA]] | access-date=31 August 2016
}}</ref><ref>{{Cite journal |doi=10.1051/0004-6361/201526329 |last1=Courcol |first1=Bastien |last2=Bouchy |first2=François |last3=Pepe |first3=Francesco |last4=Santerne |first4=Alexandre |last5=Delfosse |first5=Xavier |last6=Arnold |first6=Luc |last7=Astudillo-Defru |first7=Nicola |last8=Boisse |first8=Isabelle |last9=Bonfils |first9=Xavier |date=2015-09-01 |title=The SOPHIE search for northern extrasolar planets |url=http://www.aanda.org/10.1051/0004-6361/201526329 |journal=Astronomy & Astrophysics |language=en |volume=581 |pages=A38 |issn=0004-6361 |arxiv=1506.07144 |bibcode=2015A&A...581A..38C |s2cid=119181352 }}</ref>
* [[TOI-561]] has four, or possibly five planets. The innermost of which, [[TOI-561 b]], is notable because it is an [[ultra-short period planet]].

==Deep-sky objects==

Hercules contains two bright [[globular cluster]]s: [[Globular Cluster M13|M13]], the brightest globular cluster in the northern hemisphere{{dubious|date=June 2023}}, and [[Globular Cluster M92|M92]]. It also contains the nearly spherical [[planetary nebula]] [[Abell 39]]. M13 lies between the stars [[Eta Herculis|η Her]] and [[Zeta Herculis|ζ Her]]; it is dim, but may be detected by the unaided eye on a very clear night.

M13, visible to both the naked eye and binoculars, is a globular cluster of the 6th magnitude that contains more than 300,000 stars and is 25,200 light-years from Earth. It is also very large, with an apparent diameter of over 0.25 degrees, half the size of the [[full moon]]; its physical diameter is more than 100 light-years. Individual stars in M13 are resolvable in a small amateur telescope.<ref name=rid/>

[[Messier 92|M92]] is a globular cluster of magnitude 6.4, 26,000 light-years from earth. It is a Shapley class IV cluster, indicating that it is quite concentrated at the center; it has a very clear nucleus.<ref>{{cite book |first = David H. |last = Levy |title = Deep Sky Objects |publisher = [[Prometheus Books]] |date = 2005 |isbn = 1-59102-361-0 |page = [https://archive.org/details/deepskyobjects00davi/page/150 150] |url-access = registration |url = https://archive.org/details/deepskyobjects00davi/page/150 }}</ref> M92 is visible as a fuzzy star in binoculars, like M13; it is denser and smaller than the more celebrated cluster. The oldest globular cluster known at 14 billion years, its stars are resolvable in a medium-aperture amateur telescope.<ref name=rid/>

[[NGC 6229]] is a dimmer globular cluster, with a magnitude of 9.4, it is the third-brightest globular in the constellation. 100,000 light-years from Earth, it is a Shapley class IV cluster, meaning that it is fairly rich in the center and quite concentrated at the nucleus.<ref>{{cite book |first = David H. |last = Levy |title = Deep Sky Objects |publisher = Prometheus Books |date = 2005 |isbn = 1-59102-361-0 |page = [https://archive.org/details/deepskyobjects00davi/page/154 154] |url-access = registration |url = https://archive.org/details/deepskyobjects00davi/page/154 }}</ref>

[[NGC 6210]] is a [[planetary nebula]] of the 9th magnitude, 4000 light-years from Earth visible as a blue-green elliptical disk in amateur telescopes larger than 75&nbsp;mm in aperture.<ref name=rid/>

[[AT2018cow]], a large astronomical explosion detected on 16 June 2018.<ref name="AT-20180617">{{cite web |author=Smartt, S.J.|display-authors=etal |title=ATLAS18qqn (AT2018cow) - a bright transient spatially coincident with CGCG 137-068 (60 Mpc) |url=http://www.astronomerstelegram.org/?read=11727 |date=17 June 2018 |work=[[The Astronomer's Telegram]] |access-date=22 June 2018 }}</ref><ref name="NS-20180621">{{cite web |last=Crane |first=Leah |title=We've just seen a huge space explosion and don't know what it is |url=https://www.newscientist.com/article/2172351-weve-just-seen-a-huge-space-explosion-and-dont-know-what-it-is/ |date=21 June 2018 |work=[[New Scientist]] |access-date=22 June 2018 }}</ref> As of 22 June 2018, this [[Transient astronomical event|astronomical event]] has generated a very large amount of interest among astronomers throughout the world<ref name="AT-20180622main">{{cite web |author=Staff |title=The Astronomer's Telegram - Main Page (22 June 2018) |url=http://astronomerstelegram.org/ |date=22 June 2018 |work=[[The Astronomer's Telegram]] |url-status=dead |archive-url=https://web.archive.org/web/20180622224952/http://astronomerstelegram.org/ |archive-date=22 June 2018 |access-date=22 June 2018 }}</ref> and may be, as of 22 June 2018, considered a supernova tentatively named [[Supernova 2018cow]].<ref name="RA-20180622a">{{cite web |last=Bishop |first=David |title=Latest SuperNovae |url=http://www.rochesterastronomy.org/supernova.html#2018cow |date=22 June 2018 |work=RochesterAstronomy.org |access-date=22 June 2018 }}</ref><ref name="RA-20180622b">{{cite web |last=Bishop |first=David |title=Supernovae 2018cow in CGCG 137-068 |url=http://www.rochesterastronomy.org/sn2018/sn2018cow.html |date=22 June 2018 |work=RochesterAstronomy.org |access-date=22 June 2018 }}</ref>

The [[Hercules Cluster]] (Abell 2151) is a cluster of galaxies in Hercules.

The brightest radio source in the constellation is [[Hercules A]], an [[elliptical galaxy]] located 2.1 billion light years away with a [[supermassive black hole]] with a mass of 2.5-billion-solar-mass that has [[astrophysical jet|radio jets]] that extend for one-and-a-half million light-years.<ref>{{cite web |title=A Multi-Wavelength View of Radio Galaxy Hercules A |url=https://hubblesite.org/contents/media/images/2012/47/3110-Image.html |website=hubblesite.org |date= 29 November 2012 |access-date=30 June 2023}}</ref> Another bright radio source in Hercules is the [[quasar]] [[3C 345]] which has a  [[astrophysical jet|jet]] that appears to [[Superluminal motion|move faster than the speed of light]].<ref name="Zensus1995">{{cite journal |last1=Zensus |first1=J. A. |last2=Cohen |first2=M. H. |last3=Unwin |first3=S. C. |title=The Parsec-scale jet in quasar 3C 345 |journal=The Astrophysical Journal |date=April 1995 |volume=443 |pages=35 |url=https://articles.adsabs.harvard.edu/pdf/1995ApJ...443...35Z |doi=10.1086/175501|doi-access=free |bibcode=1995ApJ...443...35Z }}</ref>

The [[Hercules–Corona Borealis Great Wall]], the largest structure in the universe, is in Hercules.

==Visualizations==

===Traditional===
[[Image:Hercules Historical View.png|thumb|right|200px|Traditional view of the Hercules constellation highlighting the [[Quadrilateral|quadrangle]] which forms the Keystone asterism.]]
The traditional visualization imagines [[Alpha Herculis|α Herculis]] as Hercules's head; its name, [[Rasalgethi]], literally means "head of the kneeling one". Hercules's left hand then points toward Lyra from his shoulder ([[Delta Herculis|δ Herculis]]), and [[Beta Herculis|β Herculis]], or Kornephoros ("club-bearer") forms his other shoulder. His narrow waist is formed by [[Epsilon Herculis|ε Herculis]] and [[Zeta Herculis|ζ Herculis]]. His right leg is kneeling. Finally, his left leg (with [[Theta Herculis|θ Herculis]] as the knee and [[Iota Herculis|ι Herculis]] the foot) is stepping on Draco's head, the dragon/snake whom Hercules has vanquished and perpetually gloats over for eternities.<ref>{{cite book |last=Chartrand III |first=Mark R. |date=1983 |title=Skyguide: A Field Guide for Amateur Astronomers |isbn=0-307-13667-1 |page=150|publisher=Golden Press }}</ref>

=== Keystone asterism ===
[[Image:Hercules constellation map visualization.PNG|thumb|200px|right|An alternative way to connect the stars of the constellation Hercules, suggested by [[H.A. Rey]]. Here, Hercules is shown with his head at the top.]]
[[Image:Sidney Hall - Urania's Mirror - Hercules and Corona Borealis.jpg|thumb|300px|Hercules as depicted in ''[[Urania's Mirror]]'', a set of constellation cards published in London c.1825. The figure appears upside down in the sky relative to neighbouring constellations. The [[former constellation]] of [[Cerberus (constellation)|Cerberus]] is held by Hercules before its stars were part of the constellation.|alt=]]
A common form found in modern star charts uses the quadrangle formed by [[Pi Herculis|π Her]], [[Eta Herculis|η Her]], [[Zeta Herculis|ζ Her]] and [[Epsilon Herculis|ε Her]] (known as the "Keystone" [[asterism (astronomy)|asterism]]) as the lower half (abdomen) of Hercules's torso.

===H.A. Rey===
[[H. A. Rey]] has suggested an alternative visualization in which the "Keystone" becomes Hercules's head. This quadrangle lies between two very bright stars: [[Vega]] in the constellation Lyra and [[Alpha Coronae Borealis|α CrB]] (Alphecca) in the constellation [[Corona Borealis]]. The hero's right leg contains two bright stars of the third magnitude: [[Alpha Herculis|α Her]] (Rasalgethi) and [[Delta Herculis|δ Her]] (Sarin). The latter is the right knee. The hero's left leg contains dimmer stars of the fourth magnitude which do not have [[Bayer designation]]s but which do have [[Flamsteed designation|Flamsteed numbers]]. The star [[Beta Herculis|β Her]] belongs to the hero's outstretched right hand, and is also called Kornephoros.

==History==
According to Gavin White, the Greek constellation of Hercules is a distorted version of the Babylonian constellation known as the "Standing Gods" (MUL.DINGIR.GUB.BA.MESH). White argues that this figure was, like the similarly named "Sitting Gods", depicted as a man with a serpent's body instead of legs (the serpent element now being represented on the Greek star map by the figure of [[Draco (constellation)|Draco]] that Hercules crushes beneath his feet). He further argues that the original name of Hercules – the 'Kneeler' (see below) – is a conflation of the two Babylonian constellations of the Sitting and Standing Gods.<ref>''Babylonian Star-lore'' by Gavin White, Solaria Pub[-0[-[], 2008, pp. 199ff</ref>

The constellation is also sometimes associated with [[Gilgamesh]], a [[Sumer]]ian mythological hero.<ref name=rid/> [[Phoenicia]]n tradition is said to have associated this constellation with their sun god, who slew a dragon (Draco).<ref name=Condos>{{cite book | translator-first=Theony | translator-last=Condos | chapter=Hercules | title=Star Myths of the Greeks and Romans: A Sourcebook | year=1997 | publisher=Phanes Press | publication-place=Grand Rapids | isbn=9781890482930 | chapter-url=https://archive.org/details/starmythsofgreek00theo/page/117 | pages=117 }}</ref>

The earliest Greek references to the constellation do not refer to it as Hercules. [[Aratus]] describes it as follows:
<blockquote>Right there in its [Draco's] orbit wheels a Phantom form, like to a man that strives at a task. That sign no man knows how to read clearly, nor what task he is bent, but men simply call him On His Knees. [{{lang|grc|Ἐγγόνασιν}} "the Kneeler"].<ref>"Ἐγγόνασιν (ἐν γόνασιν), Arat. 66, 669, Gal. 9. 936, etc." [https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D*%29eggo%2Fnasin] Henry George Liddell and Robert Scott. ''A Greek-English Lexicon''. Oxford. Clarendon Press, 1940.</ref></blockquote>

<blockquote>Now that Phantom, that toils on his knees, seems to sit on bended knee, and from both his shoulders his hands are upraised and stretch, one this way, one that, a fathom's length. Over the middle of the head of the crooked Dragon, he has the tip of his right foot. Here too that Crown [Corona], which glorious Dionysus set to be memorial of the dead Ariadne, wheels beneath the back of the toil-spent Phantom. To the Phantom's back the Crown is near, but by his head mark near at hand the head of Ophiuchus [...] Yonder, too, is the tiny Tortoise, which, while still beside his cradle, Hermes pierced for strings and bade it be called the Lyre [Lyra]: and he brought it into heaven and set it in front of the unknown Phantom. That Croucher on his Knees comes near the Lyre with his left knee, but the top of the Bird's head wheels on the other side, and between the Bird's head and the Phantom's knee is enstarred the Lyre.<ref>[[Aratus]] [http://www.theoi.com/Text/AratusPhaenomena.html ''Phaenomena''], trans. Mair, A. W. & G. R. Loeb Classical Library Volume 129. London: William Heinemann, 1921.</ref></blockquote>

The constellation is connected with Hercules in {{lang|la|[[De astronomia]]}} (probably 1st century BCE/CE, and attributed to [[Gaius Julius Hyginus|Hyginus]]), which describes several different myths about the constellation:
* [[Eratosthenes]] (3rd century BCE) is said to have described it as Hercules, placed above Draco (representing the dragon of the [[Hesperides]]) and preparing to fight it, holding his lion's skin in his left hand, and a club in his right (this can be found in the {{lang|grc-Latn|[[Catasterismi|Epitome Catasterismorum]]}}<ref name=Hard/>).
* [[Panyassis]]' {{lang|grc-Latn|Heracleia}} (5th century BCE) reportedly said [[Jupiter]] was impressed by this fight, and made it a constellation, with Hercules kneeling on his right knee, and trying to crush Draco's head with his left foot, while striking with his right hand and holding the lion skin in his left.
* [[Ariaethus of Tegea|Araethus]] (3rd/4th century BCE) is said to have described the constellation as depicting [[Ceteus]] son of [[Lycaon (king of Arcadia)|Lycaon]], imploring the gods to restore his daughter [[Callisto (mythology)|Megisto]] who had been transformed into a bear.
* Hegesianax (2nd/3rd century BCE), who it says describes it as [[Theseus]] lifting the stone at [[Troezen]].
* Anacreon of Alexandria, who it claims also supports the idea that it depicts Theseus, saying that the constellation [[Lyra (constellation)|Lyra]] (said to be Theseus' lyre in other sources) is near Theseus.
* [[Thamyris]] blinded by the [[Muses]], kneeling in supplication.
* [[Orpheus]] killed by the women of [[Thracia]] for seeing the sacred rituals of [[Liber]] ([[Dionysus]]).
* [[Aeschylus]]' lost play ''[[Prometheus Unbound (Aeschylus)|Prometheus Unbound]]'' (5th century BCE), which recounted that when Hercules drives the cattle of [[Geryon]] through [[Liguria]] (northern [[Italy]]), the Ligurians will join forces and attack him, attempting to steal the cattle. Hercules fights until his weapons break, before falling to his knees, wounded. Jupiter, taking pity on his son, provides many stones on the ground, which Hercules uses to fight off the Ligurians. In commemoration of this, Jupiter makes a constellation depicting Hercules in his fighting form. (A quote from this section of the play is preserved in [[Dionysius of Halicarnassus]]' ''Roman Antiquities'': "And thou shalt come to Liguria's dauntless host, Where no fault shalt thou find, bold though thou art, With the fray: 'tis fated thy missiles all shall fail."<ref>{{cite web | title=Dionysius of Halicarnassus, Roman Antiquities: 1.41.3 | website=Topos Text | url=https://topostext.org/work/139#1.41.3 | access-date=2024-05-05 }}</ref>)
* [[Ixion]] with his arms bound for trying to attack [[Juno (mythology)|Juno]].
* [[Prometheus]] bound on [[Caucasus Mountains|Mount Caucasus]].<ref>{{cite web | first=Mary | last=Grant | title=Hyginus, Astronomica: 2.6 'The Kneeler' | website=[[Theoi Project]] | access-date=2017-12-24 | url=http://www.theoi.com/Text/HyginusAstronomica.html#6 | archive-date=2017-12-24 | archive-url=https://web.archive.org/web/20171224042241/http://www.theoi.com/Text/HyginusAstronomica.html#6 }}</ref>

The [[Scholia]] to Aratus mention three more mythical figures in connection with this constellation: [[Sisyphus]] or [[Tantalus]], who suffered in [[Tartarus]] for having offended the gods, or [[Salmoneus]], who was struck down by [[Zeus]] for his hubris.<ref name=Hard>{{cite book | translator-first=Robin | translator-last=Hard | chapter=Hercules, originally known as Engonasin, the Kneeler | title=Constellation Myths | year=2015 | isbn=9780191026539 | publisher=Oxford University Press }}</ref> Another classical author associated the constellation with [[Atlas (mythology)|Atlas]].<ref name=Condos/>

==Equivalents==
In [[Chinese astronomy]], the stars that correspond to Hercules are located in two areas: the [[Purple Forbidden enclosure]] (紫微垣, ''Zǐ Wēi Yuán'') and the [[Heavenly Market enclosure]] (天市垣, ''Tiān Shì Yuán'').

Arab translators of Ptolemy named it in {{Langx|ar|الرقيس|links=no|lit=the player|translit=al-raqis}}{{citation needed|date=November 2020}} (not to be confused with {{langx|ar|الراقص|translit=al-rāqiṣ|lit=the trotting (camel), the dancing one
|links=no}}), the name for the star [[Mu Draconis]].<ref name="k&s">{{cite book
  |author= Kunitzsch, P. |author2=Smart, T. |date = 2006
  |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
  |edition = 2nd rev.
  |publisher = [[Sky Publishing Corporation|Sky Pub]]
  |location = [[Cambridge, Massachusetts|Cambridge]], [[Massachusetts|MA]]
  |isbn = 978-1-931559-44-7
  |page = 35}}</ref><ref name="allen">{{cite book|title=Star Names: Their Lore and Meaning|date=1963|publisher=[[Dover Publications]] Inc.|isbn=((978-0-486-21079-7))|edition=rep.|location=[[New York City|New York]], [[New York (state)|NY]]|page=[https://archive.org/details/starnamestheirlo00alle/page/211 211]|author=Allen, R. H.|author-link=Richard Hinckley Allen|title-link=Star Names: Their Lore and Meaning}}</ref>
Hence its Swahili name {{lang|sw|Rakisi}}.{{citation needed|date=November 2020}}

==See also==
* [[Hercules (Chinese astronomy)]]

==References==
{{Reflist|30em}}

==Further reading==
* [[H. A. Rey]], ''The Stars — A New Way To See Them''. Enlarged World-Wide Edition. Houghton Mifflin, Boston, 1997. {{ISBN|0-395-24830-2}}.
* Ian Ridpath and Wil Tirion (2007). ''Stars and Planets Guide'', Collins, London. {{ISBN|978-0-00-725120-9}}. Princeton University Press, Princeton. {{ISBN|978-0-691-13556-4}}.

== External links ==
{{Commons and category}}
* [http://www.allthesky.com/constellations/hercules/ The Deep Photographic Guide to the Constellations: Hercules]
* [http://astrojan.nhely.hu/hercules.htm The clickable Hercules]
* [http://www.ianridpath.com/startales/hercules.html Star Tales – Hercules]
* [https://iconographic.warburg.sas.ac.uk/category/vpc-taxonomy-017044 Warburg Institute Iconographic Database (ca 160 medieval and early modern images of Hercules)]

{{Stars of Hercules}}
{{Constellations}}
{{Portal bar|Astronomy|Stars|Outer space}}
{{Authority control}}
{{Sky|17|00|00|+|30|00|00|10}}

{{DEFAULTSORT:Hercules}}
[[Category:Hercules (constellation)| ]]
[[Category:Constellations]]
[[Category:Northern constellations]]
[[Category:Constellations listed by Ptolemy]]
[[Category:Hercules]]