Wikipedia

Hercules (constellation)

Herculesis astarnamed afterHercules,theRoman mythologyhero adapted from theGreekheroHeracles.Hercules was one of the 48 constellations listed by the second-centuryastronomerPtolemy,and it remains one of the88 modern constellationstoday. It is the fifth-largest of the modern constellations and is the largest ofthe 50which have no stars brighter than apparentmagnitude+2.5.

Hercules
Constellation
Hercules
List of stars in Hercules
AbbreviationHer
GenitiveHerculis[1]
Pronunciation/ˈhɜːrkjʊliːz/,
genitive/ˈhɜːrkjʊlɪs/
SymbolismHeracles
Right ascension17h
Declination+30°
QuadrantNQ3
Area1225 sq. deg. (5th)
Main stars14, 22
Bayer/Flamsteed
stars		1020
Stars withplanets15
Stars brighter than 3.00m2
Stars within 10.00 pc (32.62 ly)9
Brightest starβ Her(Kornephoros) (2.78m)
Messier objects2
Meteor showersTau Herculids
Bordering
constellations		Draco
Boötes
Corona Borealis
Serpens Caput
Ophiuchus
Aquila
Sagitta
Vulpecula
Lyra[1]
Visible at latitudes between +90° and −50°.
Best visible at 21:00 (9 p.m.) during the month ofJuly.

Characteristics

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The constellation Hercules as it may appear to thenaked eye.

Hercules is bordered byDracoto the north;Boötes,Corona Borealis,andSerpens Caputto the west;Ophiuchusto the south;Aquilato the southwest; andSagitta,Vulpecula,andLyrato the east. Covering 1225.1 square degrees and 2.970% of the night sky, it ranks fifth among the 88 constellations in size.[2]The three-letter abbreviation for the constellation, as adopted by theInternational Astronomical Unionin 1922, is 'Her'.[3]The official constellation boundaries, as set byEugène Delportein 1930, are defined by a polygon of 32 segments (illustrated in infobox). In theequatorial coordinate system,epoch 2000, theright ascensioncoordinates of these borders lie between16h00m26.64sand18h57m49.50s,while thedeclinationcoordinates are between +3.67° and +51.32°.[4]In mid-northern latitudes, Hercules is best observed from mid-spring until early autumn,culminatingat midnight on June 13.[1]

Thesolar apexis the direction of the open motion with respect to theLocal Standard of Rest.This is located within the constellation of Hercules, around coordinates right ascension18h00mand declination 30° 00′.[5]The north pole of thesupergalactic coordinate systemis located within this constellation at right ascension18h55m01sand declination +15° 42′ 32″.[6]

Stars

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See also:List of stars in Hercules

Hercules has nofirst or second magnitudestars. However, it does have several stars above magnitude 4.Alpha Herculis,traditionally called Rasalgethi, is atriple starsystem, partly resolvable in small amateur telescopes, 359 light-years from Earth. Its common name means "the kneeler's head".[7]The primary is an irregularvariable star;it is abright giantwith a minimum magnitude of 4 and a maximum magnitude of 3. It has a diameter of roughly 400solar diameters.[8]The secondary, aspectroscopic binarythat 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 ayellow giantof magnitude 2.8, 148 light-years from Earth; kornephoros means club-bearer.[9]Delta HerculisA 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 Herculisis also a double star divisible in small amateur telescopes. The primary is awhite giantof magnitude 3.8, 195 light-years from Earth. The optical companion, widely separated, is 10th magnitude.Zeta Herculisis 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.[10]

Hercules hosts further quite bright double stars and binary stars.Kappa Herculisis 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 anorange giantof magnitude 6.3, 470 light-years from Earth.Rho Herculisis 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 Herculisis 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 Herculisis 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.[10]

There are several dimmervariable starsin Hercules.30 Herculis,also called g Herculis, is asemiregularred giantwith 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 aBeta Lyrae-typeeclipsing binarystar. 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.[10]

Mu Herculisis 27.4light-yearsfrom Earth. Thesolar apex,i.e., the point on the sky which marks the direction that the Sun is moving in its orbit around the center of theMilky Way,narrowly figures in Hercules,[11]between Hercules' left elbow (nearOmicron Herculis) andVega(in neighboringLyra).

Planetary systems

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Fifteen stars in Hercules are known to be orbited byextrasolar planets.

Deep-sky objects

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Hercules contains two brightglobular clusters:M13,the brightest globular cluster in the northern hemisphere[dubious–discuss],andM92.It also contains the nearly sphericalplanetary nebulaAbell 39.M13 lies between the starsη Herandζ 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 thefull moon;its physical diameter is more than 100 light-years. Individual stars in M13 are resolvable in a small amateur telescope.[10]

M92is 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.[24]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.[10]

NGC 6229is 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.[25]

NGC 6210is aplanetary nebulaof the 9th magnitude, 4000 light-years from Earth visible as a blue-green elliptical disk in amateur telescopes larger than 75 mm in aperture.[10]

AT2018cow,a large astronomical explosion detected on 16 June 2018.[26][27]As of 22 June 2018, thisastronomical eventhas generated a very large amount of interest among astronomers throughout the world[28]and may be, as of 22 June 2018, considered a supernova tentatively namedSupernova 2018cow.[29][30]

TheHercules Cluster(Abell 2151) is a cluster of galaxies in Hercules.

The brightest radio source in the constellation isHercules A,anelliptical galaxylocated 2.1 billion light years away with asupermassive black holewith a mass of 2.5-billion-solar-mass that hasradio jetsthat extend for one-and-a-half million light-years.[31]Another bright radio source in Hercules is thequasar3C 345which has ajetthat appears tomove faster than the speed of light.[32]

TheHercules–Corona Borealis Great Wall,the largest structure in the universe, is in Hercules.

Visualizations

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Traditional

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Traditional view of the Hercules constellation highlighting thequadranglewhich forms the Keystone asterism.

The traditional visualization imaginesα Herculisas Hercules's head; its name,Rasalgethi,literally means "head of the kneeling one". Hercules's left hand then points toward Lyra from his shoulder (δ Herculis), andβ Herculis,or Kornephoros ( "club-bearer" ) forms his other shoulder. His narrow waist is formed byε Herculisandζ Herculis.His right leg is kneeling. Finally, his left leg (withθ Herculisas the knee andι Herculisthe foot) is stepping on Draco's head, the dragon/snake whom Hercules has vanquished and perpetually gloats over for eternities.[33]

Keystone asterism

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An alternative way to connect the stars of the constellation Hercules, suggested byH.A. Rey.Here, Hercules is shown with his head at the top.
Hercules as depicted inUrania's Mirror,a set of constellation cards published in London c.1825. The figure appears upside down in the sky relative to neighbouring constellations. Theformer constellationofCerberusis held by Hercules before its stars were part of the constellation.

A common form found in modern star charts uses the quadrangle formed byπ Her,η Her,ζ Herandε Her(known as the "Keystone"asterism) as the lower half (abdomen) of Hercules's torso.

H.A. Rey

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H. A. Reyhas suggested an alternative visualization in which the "Keystone" becomes Hercules's head. This quadrangle lies between two very bright stars:Vegain the constellation Lyra andα CrB(Alphecca) in the constellationCorona Borealis.The hero's right leg contains two bright stars of the third magnitude:α Her(Rasalgethi) andδ Her(Sarin). The latter is the right knee. The hero's left leg contains dimmer stars of the fourth magnitude which do not haveBayer designationsbut which do haveFlamsteed numbers.The starβ Herbelongs to the hero's outstretched right hand, and is also called Kornephoros.

History

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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 ofDracothat 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.[34]

The constellation is also sometimes associated withGilgamesh,aSumerianmythological hero.[10]Phoeniciantradition is said to have associated this constellation with their sun god, who slew a dragon (Draco).[35]

The earliest Greek references to the constellation do not refer to it as Hercules.Aratusdescribes it as follows:

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. [Ἐγγόνασιν"the Kneeler" ].[36]

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.[37]

The constellation is connected with Hercules inDe astronomia(probably 1st century BCE/CE, and attributed toHyginus), 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 theHesperides) 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 theEpitome Catasterismorum[38]).
  • Panyassis'Heracleia(5th century BCE) reportedly saidJupiterwas 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.
  • Araethus(3rd/4th century BCE) is said to have described the constellation as depictingCeteusson ofLycaon,imploring the gods to restore his daughterMegistowho had been transformed into a bear.
  • Hegesianax (2nd/3rd century BCE), who it says describes it asTheseuslifting the stone atTroezen.
  • Anacreon of Alexandria, who it claims also supports the idea that it depicts Theseus, saying that the constellationLyra(said to be Theseus' lyre in other sources) is near Theseus.
  • Thamyrisblinded by theMuses,kneeling in supplication.
  • Orpheuskilled by the women ofThraciafor seeing the sacred rituals ofLiber(Dionysus).
  • Aeschylus' lost playPrometheus Unbound(5th century BCE), which recounted that when Hercules drives the cattle ofGeryonthroughLiguria(northernItaly), 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 inDionysius 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."[39])
  • Ixionwith his arms bound for trying to attackJuno.
  • Prometheusbound onMount Caucasus.[40]

TheScholiato Aratus mention three more mythical figures in connection with this constellation:SisyphusorTantalus,who suffered inTartarusfor having offended the gods, orSalmoneus,who was struck down byZeusfor his hubris.[38]Another classical author associated the constellation withAtlas.[35]

Equivalents

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InChinese astronomy,the stars that correspond to Hercules are located in two areas: thePurple Forbidden enclosure( tử vi viên,Zǐ Wēi Yuán) and theHeavenly Market enclosure( thiên thị viên,Tiān Shì Yuán).

Arab translators of Ptolemy named it in Arabic:الرقيس,romanized:al-raqis,lit. 'the player'[citation needed](not to be confused with Arabic:الراقص,romanized:al-rāqiṣ,lit. 'the trotting (camel), the dancing one'), the name for the starMu Draconis.[41][42] Hence its Swahili nameRakisi.[citation needed]

See also

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References

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Further reading

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