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Hercules (constellation)

Hercules (constellation)

Overview
Hercules is a constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 named after Hercules
Hercules
Hercules is the Roman name for Greek demigod Heracles, son of Zeus , and the mortal Alcmene...

, the Roman mythological hero adapted from the Greek
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

 hero Heracles
Heracles
Heracles ,born Alcaeus or Alcides , was a divine hero in Greek mythology, the son of Zeus and Alcmene, foster son of Amphitryon and great-grandson of Perseus...

. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

, and it remains one of the 88 modern constellations today. It is the fifth largest of the modern constellations.


Hercules has no first magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 stars.

Mu Herculis
Mu Herculis
Mu Herculis is a nearby star system about 27.1 light years from Earth in the constellation Hercules. Its main star, Mu Herculis A is fairly similar to the Sun although more highly evolved with a...

 is 27.4 light years from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. The solar apex
Solar apex
The solar apex is the direction that the Sun travels with respect to the Local Standard of Rest. In lay terms, it's the "target" within the Milky Way that the Sun appears to be "chasing" as it orbits the galaxy...

, i.e., the point on the sky which marks the direction that the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 is moving in its orbit around the center of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

, is located within Hercules, close to Vega
Vega
Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...

 in neighboring Lyra
Lyra
Lyra is a small constellation. It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations recognized by the International Astronomical Union. Its principal star, Vega — a corner of the Summer Triangle — is one of the brightest...

.

Eleven stars in Hercules are known to be orbited by extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

s.
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Encyclopedia
Hercules is a constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 named after Hercules
Hercules
Hercules is the Roman name for Greek demigod Heracles, son of Zeus , and the mortal Alcmene...

, the Roman mythological hero adapted from the Greek
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

 hero Heracles
Heracles
Heracles ,born Alcaeus or Alcides , was a divine hero in Greek mythology, the son of Zeus and Alcmene, foster son of Amphitryon and great-grandson of Perseus...

. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

, and it remains one of the 88 modern constellations today. It is the fifth largest of the modern constellations.

Stars



Hercules has no first magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 stars.

Mu Herculis
Mu Herculis
Mu Herculis is a nearby star system about 27.1 light years from Earth in the constellation Hercules. Its main star, Mu Herculis A is fairly similar to the Sun although more highly evolved with a...

 is 27.4 light years from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. The solar apex
Solar apex
The solar apex is the direction that the Sun travels with respect to the Local Standard of Rest. In lay terms, it's the "target" within the Milky Way that the Sun appears to be "chasing" as it orbits the galaxy...

, i.e., the point on the sky which marks the direction that the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 is moving in its orbit around the center of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

, is located within Hercules, close to Vega
Vega
Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...

 in neighboring Lyra
Lyra
Lyra is a small constellation. It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations recognized by the International Astronomical Union. Its principal star, Vega — a corner of the Summer Triangle — is one of the brightest...

.

Planetary systems


Eleven stars in Hercules are known to be orbited by extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

s. These planets were discovered one in 1996, two in 2005, two in 2006, four in 2007, one in 2009, and one in 2010.
  • 14 Herculis
    14 Herculis
    14 Herculis or 14 Her is an orange dwarf star approximately 59 light-years away in the constellation Hercules. Because of its apparent magnitude, the star cannot be seen with the naked eye...

      has one confirmed and one unconfirmed planet. The planet 14 Herculis b
    14 Herculis b
    14 Herculis b or 14 Her b is an extrasolar planet approximately 59 light-years away in the constellation of Hercules. The planet was found orbiting the star 14 Herculis, with a mass that would likely make the planet a Jovian planet roughly the same size as Jupiter but much more massive. It was...

     had the longest period (4.9 years) and widest orbit (2.8 AU
    Astronomical unit
    An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....

    ) at the time of discovery. The planet 14 Herculis c
    14 Herculis c
    14 Herculis c or 14 Her c is an extrasolar planet approximately 59 light-years away in the constellation of Hercules. The planet was found orbiting the star 14 Herculis, with a mass that would likely make the planet a gas giant roughly the same size as Jupiter but much more massive. This planet...

     orbits much further out with very low eccentricity.

  • HD 149026
    HD 149026
    HD 149026 is a yellow subgiant star approximately 257 light-years away in the constellation of Hercules. The star is thought to be much more massive, larger, and brighter than the Sun. , an extrasolar planet has been confirmed to be orbiting the star...

     has a transiting hot Jupiter
    Hot Jupiter
    Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...

     planet
    HD 149026 b
    HD 149026 b is an extrasolar planet approximately 257 light-years away in the constellation of Hercules. The planet was discovered after it transited its parent star, HD 149026...

     and is one of the most prominent and studied.

  • HD 154345
    HD 154345
    HD 154345 is a G-type dwarf star located in northern Hercules. It is not visible to the naked eye since this star is below +6.50 magnitude, but using binoculars it is an easy target.-Planetary system:...

     has the planet HD 154345 b
    HD 154345 b
    HD 154345 b, is a Jupiter-sized extrasolar planet orbiting the star HD 154345.-Discovery:Wright et al. discovered the planet in March 2006 using the radial velocity method to detect the small wobbling movement of the star caused by the gravity of the planet...

    , a long period (9.095 years) and wide orbit (4.18 AU).

  • HD 164922
    HD 164922
    HD 164922 is a seventh magnitude star in the constellation of Hercules. It is an orange dwarf with a spectral type K0V. To view it, binoculars or a telescope are necessary, as it is too faint to be visible to the naked eye. It is 71.5 light years distant from the Earth. At an age of 13.4 billion...

     has the first long period Saturian planet
    HD 164922 b
    HD 164922 b is an extrasolar planet orbiting around orange dwarf star HD 164922, located in Hercules constellation at a distance of 71.5 light years from Earth. Its inclination is not known, and its true mass may be significantly greater than the radial velocity lower limit of 0.36 Jupiter masses...

     discovered. The mass
    Mass
    Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

     is 0.36 MJ and semimajor axis of 2.11 AU.

  • HD 147506
    HD 147506
    HD 147506 is a magnitude 8.7 F8 dwarf star that is somewhat larger and hotter than our sun. The star is 440 light years from Earth and is positioned near the keystone of Hercules.It is estimated to be 2 to 3 billion years old.- Planetary system :...

     has the most massive transiting planet HAT-P-2b
    HAT-P-2b
    HAT-P-2b is an extrasolar planet detected by the HATNet Project in May 2007. It orbits a class F star, , located about 440 light-years away in the constellation Hercules...

     at the time of discovery. The mass is 8.65 MJ.

  • HD 155358
    HD 155358
    HD 155358 is a low metallicity yellow dwarf star approximately 43 light years away in the constellation Hercules. This star is known to be orbited by two extrasolar planets.The star is 11.9 billion years old and has a mass 0.89 times that of the Sun...

     has two planets around the lowest metallicity
    Metallicity
    In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...

     planet-harboring star (21% Sun). Both planets orbit in mild eccentricities.

  • GSC 03089-00929
    GSC 03089-00929
    GSC 03089-00929 is a magnitude 12 star located approximately 1300 light-years away in the constellation of Hercules. This star is a G type main sequence star that is similar to but slightly cooler than our sun....

     has a short transiting planet TrES-3
    TrES-3
    TrES-3b is an extrasolar planet orbiting the star GSC 03089-00929. It has an orbital period of just 31 hours and is undergoing orbital decay due to tidal effects. It has nearly twice the mass of Jupiter....

    . The period
    Orbital period
    The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...

     was 31 hours and undergoing orbital decay
    Orbital decay
    Orbital decay is the process of prolonged reduction in the altitude of a satellite's orbit.This can be due to drag produced by an atmosphere due to frequent collisions between the satellite and surrounding air molecules. The drag experienced by the object is larger in the case of increased solar...

    .

  • Gliese 649
    Gliese 649
    Gliese 649 is a red dwarf star in the constellation of Hercules, located roughly 34 light years from Sun. The star has been found to host an extrasolar planet.- A planetary companion :...

     has a saturnian planet
    Gliese 649 b
    Gliese 649 b , or Gl 649 b is an extrasolar planet, orbiting the 10th magnitude M-type star Gliese 649, 10 parsecs from earth. This planet is a sub-Jupiter, massing 0.328 Jupiter mass and orbits at 1.135 AU....

     around the red dwarf star.

  • HD 156668
    HD 156668
    HD 156668 is an orange dwarf star found in the Hercules constellation which is approximately 78.4 light-years away from the earth. The star has only about 27% of the Sun’s bolometric luminosity including a mass approximately 72% less and about 75% of its diameter...

     has a 4.15 Earth mass planet
    HD 156668 b
    HD 156668 b is an extrasolar planet orbiting the star HD 156668 78.5 light-years away in the constellation Hercules. It has a minimum mass of 3.1 Earth masses. At the time of discovery it was the second least massive planet discovered by the radial velocity method, subject to the mass/inclination...

    , which is the second lightest planet detected by radial velocity.

Deep sky objects


Hercules contains two of the most conspicuous globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...

s: M13, the brightest globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...

 in the northern hemisphere (containing 300,000 stars), and M92. It also contains the nearly spherical planetary nebula
Planetary nebula
A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life...

 Abell 39
Abell 39
Abell 39 is a low surface brightness planetary nebula in the constellation of Hercules. It is the 39th entry in George Abell's 1966 Abell Catalog of Planetary Nebulae of 86 old planetary nebulae which either Abell or Albert George Wilson discovered before August 1955 as part of the National...

. M13 lies between the stars η Her
Eta Herculis
Eta Herculis is a fourth-magnitude star in the constellation Hercules. It has the traditional name Sophian, possibly from the Arabic نقي meaning "pure"" or from the Greek σοφία meaning "wisdom".- Properties :...

 and ζ Her; it is dim, but may be detected by the non-aided eye on a very clear night.

Traditional



The traditional visualization imagines α Herculis as Hercules's head; its name, Ras Algethi, literally means "head of the kneeling one". Hercules's left hand then points toward Lyra from his shoulder (Delta Herculis), and Beta Herculis forms his other shoulder. His narrow waist is formed by Epsilon and Zeta Herculis. Finally, his left leg (with Theta as the knee and Iota the foot) is stepping on Draco's head, the dragon/snake who Hercules has vanquished and perpetually gloats over for eternities.

Keystone asterism




A common form found in modern star charts uses the quadrangle formed by π Her
Pi Herculis
Pi Herculis is a fourth-magnitude star in the constellation Hercules. As one of the four stars in the Keystone asterism is one of the more easily recognized in the constellation.- Properties :...

, η Her
Eta Herculis
Eta Herculis is a fourth-magnitude star in the constellation Hercules. It has the traditional name Sophian, possibly from the Arabic نقي meaning "pure"" or from the Greek σοφία meaning "wisdom".- Properties :...

, ζ Her and ε Her
Epsilon Herculis
Epsilon Herculis is a fourth-magnitude spectroscopic binary star in the constellation Hercules. It has the traditional name Cujam....

 (known as the "Keystone" asterism
Asterism (astronomy)
In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one. Like constellations, asterisms are in most cases composed of stars which, while they are visible in the same general direction,...

) as 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
Vega
Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...

 in the constellation Lyra and α CrB (Gemma, or Alphecca) in the constellation Corona Borealis
Corona Borealis
Corona Borealis is a small constellation in the northern sky. Its name is Latin for "northern crown", a name inspired by its shape; its main stars form a semicircular arc. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy and remains one of the 88 modern...

. The hero's right leg contains two bright stars of the third magnitude: α Her
Alpha Herculis
Alpha Herculis is a multiple star system in the constellation Hercules. It has the traditional name Rasalgethi or Ras Algethi , and the Flamsteed designation 64 Herculis...

 (Ras Algethi) and δ Her
Delta Herculis
Delta Herculis is a fourth-magnitude star in the constellation Hercules. It has the traditional name Sarin....

 (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
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...

s but which do have Flamsteed numbers
Flamsteed designation
Flamsteed designations for stars are similar to Bayer designations, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation it lies in...

. The star β Her
Beta Herculis
Beta Herculis , which also has the name Kornephoros, is the brightest star in the constellation of Hercules. It has an apparent visual magnitude which varies between 2.76 and 2.81.Although β Herculis appears to the naked eye to be a single star, W. W...

 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
Draco
Draco was the first legislator of Athens in Ancient Greece. He replaced the prevailing system of oral law and blood feud by a written code to be enforced only by a court...

 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.

The earliest Greek references to the constellation do not refer to it as Hercules. Aratus
Aratus
Aratus was a Greek didactic poet. He is best known today for being quoted in the New Testament. His major extant work is his hexameter poem Phaenomena , the first half of which is a verse setting of a lost work of the same name by Eudoxus of Cnidus. It describes the constellations and other...

 describes 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 [ "the Kneeler"].


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 stings 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.


The story connecting Hercules with the constellation is recounted by Dionysius of Halicarnassus
Dionysius of Halicarnassus
Dionysius of Halicarnassus was a Greek historian and teacher of rhetoric, who flourished during the reign of Caesar Augustus. His literary style was Attistic — imitating Classical Attic Greek in its prime.-Life:...

:
On his way back to Mycenae
Mycenae
Mycenae is an archaeological site in Greece, located about 90 km south-west of Athens, in the north-eastern Peloponnese. Argos is 11 km to the south; Corinth, 48 km to the north...

 from Iberia
Iberia
The name Iberia refers to three historical regions of the old world:* Iberian Peninsula, in Southwest Europe, location of modern-day Portugal and Spain** Prehistoric Iberia...

 having obtained the Cattle of Geryon
Geryon
In Greek mythology, Geryon , son of Chrysaor and Callirrhoe and grandson of Medusa, was a fearsome giant who dwelt on the island Erytheia of the mythic Hesperides in the far west of the Mediterranean. A more literal-minded later generation of Greeks associated the region with Tartessos in southern...

 as his tenth labour Heracles came to Liguria
Liguria
Liguria is a coastal region of north-western Italy, the third smallest of the Italian regions. Its capital is Genoa. It is a popular region with tourists for its beautiful beaches, picturesque little towns, and good food.-Geography:...

 in North-Western Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 where he engaged in battle with two giants, Albion
Alebion
In Greek mythology, Alebion or Albion was a son of Poseidon and brother of Bergion who attacked Heracles with Dercynus when he passed through their country, Liguria in North-Western Italy, on his way back to Mycenae from Iberia having obtained the Cattle of Geryon as his tenth labour.The battle...

 and Bergion
Bergion
In Greek mythology, Bergion or Dercynus was a son of Poseidon and brother of Alebion. The two brothers engaged into battle with Heracles at Liguria of North-Western Italy.This version was mentioned in Aeschylus' play Promētheus Lyomenos, now lost....

 or Dercynus. The opponents were strong; Hercules was in a difficult position so he prayed to his father Zeus
Zeus
In the ancient Greek religion, Zeus was the "Father of Gods and men" who ruled the Olympians of Mount Olympus as a father ruled the family. He was the god of sky and thunder in Greek mythology. His Roman counterpart is Jupiter and his Etruscan counterpart is Tinia.Zeus was the child of Cronus...

 for help. With the aegis of Zeus, Heracles won the battle. It was this kneeling position of Heracles when prayed to his father Zeus that gave the name "the Kneeler". and Hyginus
Hyginus
Hyginus can refer to:People:*Gaius Julius Hyginus , Roman poet, author of Fabulae, reputed author of Poeticon astronomicon*Hyginus Gromaticus, Roman surveyor*Pope Hyginus, also a saint, Bishop of Rome about 140...


Equivalents


In Chinese astronomy
Chinese astronomy
Astronomy in China has a very long history, with historians considering that "they [the Chinese] were the most persistent and accurate observers of celestial phenomena anywhere in the world before the Arabs."...

, the stars that correspond to Hercules are located in two areas: the Purple Forbidden enclosure
Purple Forbidden enclosure
The Purple Forbidden enclosure is one of the San Yuan or Three enclosures. Stars and constellations of this group lie near the north celestial pole and visible all year from temperate latitudes in the Northern Hemisphere.-Asterisms:The asterisms are :...

 (紫微垣, Zǐ Wēi Yuán) and the Heavenly Market enclosure
Heavenly Market enclosure
Tian Shi Yuan, the Heavenly Market Enclosure , is one of the San Yuan or Three enclosures. Stars and constellations of this group are visible during late summer and early autumn in the Northern Hemisphere . The summer triangle lies directly to the northwest.-Asterisms:The asterisms are :...

(天市垣, Tiān Shì Yuán).

External links