Hercules Constellation aka the Kneeler
The Hercules Constellation is one of the largest constellations. It has an area of 1, 225 square degrees, occupying about 2.970% of the overall night sky. Among the 88 modern constellations, we have today, it ranks as the fifth in terms of size. It has been recognized in the night sky as early as Sumerian times. Astronomer Ptolemy included it in the Almagest, one of the earliest accounts of the sky, in the second century.
The name of this constellation is from Hercules, Roman translation of the Greek name Heracles. He is a demigod. His parents are the god Zeus and the human Alcmene. He is one of the most popular characters in Greek mythology. Another hero associated with this constellation is Gilgamesh, dating back to the Sumerian civilization.
Some people call the Hercules constellation “the Strong Man” in reference to his superhuman strength which helped him in his many conquests. One of these is the familiar story of his Twelve Labours. Others call it “the Kneeling One” or “the Kneeler,” from the Greek word Engonasin. It describes the demigod’s position in one of the many tales related to him. We can learn more about it in the mythology related to Hercules constellation.
Hercules belongs to a family of constellations named after it. The Hercules Family of constellations is made up of 19 members, making it the largest of the eight groups by Donald H. Menzel. They were not grouped mainly because of common origin or mythology. Rather, they are taken as one group because of their proximity or the closeness of their positions in the sky.
Hercules Family of Constellations
What Does Hercules Look Like?
We can easily identify the form of the hero Hercules in the night sky by first finding the Keystone asterism.
The Keystone Asterism
The Keystone asterism is a quadrangle (quadrilateral) that forms the torso or the head of Hercules, depending on sources. This asterism is made up of four stars in this constellation. These stars are Zeta Herculis, Epsilon Herculis, Eta Herculis, and Pi Herculis.
Hercules is often depicted in the night sky as if he is kneeling, holding a club in his left hand. He is stepping on the head of Draco the Dragon on his left foot like this:
The combination of shapes and lines makes us see a person’s form in the photo above. We can see two arms and feet as well as a body. The triangle forms the head of Hercules. It is marked by the star Alpha Herculis. The Keystone asterism forms Hercules’s torso.
A similar visualization of the constellation still has the Keystone asterism as the hero’s torso, this time just missing some lines. Its upside-down in the photo below:
In a newer one suggested by H. A. Rey, the Keystone asterism forms the head of Hercules. The shape of the club is also very noticeable in this version.
Some people confuse the Hercules constellation with the constellation of Orion. It might be because of the stars that seem to form their belts. One way to know the difference is that Orion’s Belt is made up of three stars while Hercules has two stars only from the Keystone.
Where To See the Hercules Constellation
The constellation of Hercules is located in the northern hemisphere of the celestial sphere. Specifically, it is in NQ3 or the third quadrant. It has the coordinates 17 hours right ascension and +30° declination. From here on Earth, it can be seen between latitudes +90° and −50°.
Hercules and His Neighbors
The Hercules constellation is surrounded by nine other constellations. We can use them as references to spot the Kneeling One. Starting near his head, these constellations are Ophiuchus the Serpent Bearer, Aquila the Eagle, Sagitta the Arrow, Vulpecula the Fox, Lyra the Lyre, Draco the Dragon, Boötes the Herdsman, Corona Borealis the Northern Crown, and Serpens Caput (Serpent Head).
In the picture above, we can see that Hercules is in the middle of two bright stars. These are Vega and Arcturus, both the brightest stars in the constellations of Lyra and Boötes respectively.
When To See the Hercules Constellation
Hercules is a seasonal constellation. Unlike circumpolar constellations like Ursa Major, it is not always visible in the night sky. Although the constellation of the Celestial Strongman lies in the Nothern Sky, it is still visible in some areas of the Southern Hemisphere.
When it does appear high in the night sky, we can enjoy stargazing outside because it is a summer constellation in the Northern Hemisphere. The time to see it best is in July at about 9 pm. During that time, it is winter in the Southern Hemisphere. Hercules looks upside down from observers below the equator.
Hercules and His Stars
The Hercules constellation occupies a big part of the sky but it does not have first or second magnitude stars. But even if the brightest stars are not from there, its stars are also marvels of their own. The International Astronomical Union (IAU) has formally given names to 11 stars in this constellation. On top of that, about 12 to 15 of its stars are discovered to have planets.
1. Alpha Herculis (α Herculis)
Alpha Herculis was traditionally known as Rasalgethi. It is a multiple star system 360 light-years away from us. The two components resolved are Alpha Herculis A and B. They complete their orbit at a period of about 3600 years.
● Alpha Herculis A (α Herculis A)
Alpha Herculis A is a semiregular variable M-type star. It is already in the late stages of its life. Because of its variability, its brightness can change between the third to the fourth magnitude.
As the primary star in this star system, Alpha Herculis A is formally named Rasalgethi. This name is Arabic in origin, which means “head of the kneeler.” It describes the position of this star in the constellation of Hercules.
● Alpha Herculis B (α Herculis B)
Alpha Herculis B is a binary star system. It is made up of two yellow stars with an orbital period of about 52 days.
2. Beta Herculis (β Herculis)
Beta Herculis is formally named Kornephoros We can see it in the naked eye because it has an apparent magnitude of 2.81. It is actually the brightest star in the constellation of Hercules, not Alpha Herculis. Kornephoros is a binary star system. It is made up of a giant G-type star and a component smaller than our Sun.
The name Kornephoros is from Greek. It means “club bearer,” which is a good description. We can see it as Hercules’s arm that holds the club. This star is located at a distance of 139 light-years.
3. Gamma Herculis (γ Herculis)
Gamma Herculis is a binary system. It has an apparent magnitude of 3.75. The primary of this spectroscopic binary has a stellar classification of A9III. Much is still unknown about its second component.
Gamma Herculis is a suspected variable star. Its apparent magnitude changes between 3.74 to 3.81. The distance of this star to us is about 193 light-years.
4. Delta Herculis (δ Herculis)
Delta Herculis is a star system with multiple stars. It marks the left shoulder of Hercules in the constellation. It has a distance of about 75 light-years from our Sun. The apparent magnitude of the system is 3.126 making it the third brightest star in the constellation of the Kneeler. The components are designated A, B, C, and D.
The component Delta Herculis A is a binary composed of Aa and Ab. Delta Herculis Aa is officially called Sarin.
5. Epsilon Herculis (ε Herculis)
Epsilon Herculis is a multiple star system. It is made up of spectral type A stars. This system is 155 light-years away, with an overall apparent magnitude of 3.9111. It is one of the stars that make up the Keystone asterism. We can see it forming Hercules’s hips together with the star Zeta Herculis.
6. Zeta Herculis (ζ Herculis)
Zeta Herculis is one of the stars forming the Keystone asterism, marking the hips of Hercules. It is the brightest of the four having an apparent magnitude of 2.81. It lies 35 light-years away from us. This multiple star system is made up of the primary Zeta Herculis A and the secondary component Zeta Herculis B. The primary is a subgiant star with a stellar classification of F9 IV.
7. Eta Herculis (η Herculis)
The main sequence star Eta Herculis has an apparent magnitude of 3.487. It is a double star with a stellar classification of G7.5IIIb. Though it is a G-type star like our Sun, it is more massive. It has a radius that is 9.8 times that of our Sun’s and 2.3 solar masses.
Eta Herculis is one of the stars in the Keystone asterism. It is also called by the name Sophian. It is about 112 light-years away from us.
8. Theta Herculis (θ Herculis)
Theta Herculis is formally named Rukbalgethi Genubi. This name means “the southern knee.” It describes the position of this star in the Hercules constellation. Rukbalgethi Genubi is a giant star whose apparent magnitude changes between 3.7 to 4.1 because it is an irregular variable. Its stellar classification is K1IIaCN2.
Rukbalgethi Genubi is said to be 130 million years old. It lies at a distance of about 750 light-years from the Sun.
9. Iota Herculis (ι Herculis)
Iota Herculis marks Hercules’s foot stepping on Draco the Dragon. It is a multiple star system composed of four stars. We can see it in the naked eye as its apparent magnitude is 3.7497. This subgiant star has a stellar classification of B3IV. Its mass is 6.5 times that of the Sun’s and it radiates with the brightness of 2,500 Suns. It is about 455 light-years away from our Sun.
Iota Herculis will become the pole star of the north in the future as it is near the Earth’s precessional path.
10. Kappa Herculis (κ Herculis)
Kappa Herculis is a double star that is about 390 light-years away. The primary component is a G-type giant star. It is formally called Marsic, the traditional name of the Kappa Herculis system. Marsic has an apparent magnitude of 5.0 while the secondary is a fainter star, with an apparent magnitude of about 6.25.
11. Lambda Herculis (λ Herculis)
Lambda Herculis is a K-type star with an apparent magnitude of about 4.4. It is formally named Maasym. The name has an Arabic origin, from the word miʽṣam meaning “wrist.” This red giant is 370 light-years away from our Sun.
12. Mu Herculis (μ Herculis)
Mu Herculis is a multiple star system that is 27.1 light-years from us. The primary is a subgiant that belongs in the G class. It has a low-mass companion. The secondary component is a binary with an orbital period of about 43 years.
Mu Herculis is also called Marfak Al Jathih Al Aisr. This traditional name means “the left elbow of the kneeling man.”
13. Nu Herculis (v Herculis)
Nu Herculis is a binary that lies at a distance of 860 light-years from us. Its spectral type is F2 II. This giant is nearly 800 times brighter than the Sun. The apparent magnitude of Nu Herculis is 4.4. It is likely a semiregular variable with a period of 29 days.
14. Xi Herculis (ξ Herculis)
Xi Herculis has an apparent magnitude of 3.70 so we can see it in the naked eye. This red clump star is 2.5 billion years old. Its mass equals two solar masses and it is more luminous than the Sun by more than 50 times. Xi Herculis lies 137 light-years away from the Sun.
15. Omicron Herculis (o Herculis)
Omicron Herculis is a multiple star system with a spectral class of B9.5V. It is a Gamma Cassiopeiae variable with an apparent magnitude of 3.83.
In the far future, at about 3 million years, its apparent magnitude will be -0.4, making it the brightest star in the night sky. This is because Omicron Herculis is close to the solar apex.
16. Pi Herculis (π Herculis)
Pi Herculis has a stellar classification of K3 II and an apparent magnitude of 3.15. The mass of this star is 4.5 times that of our Sun’s. It is 377 light-years away from the solar system and shines with the luminosity of 1,330 Suns.
Pi Herculis is one of the four stars that complete the Keystone asterism together with Epsilon Herculis, Eta Herculis, and Zeta Herculis.
17. Rho Herculis (ρ Herculis)
Rho Herculis is a binary star that is composed of an A-type giant and a B-type subgiant. The giant primary has an apparent magnitude of 4.510 while the secondary is fainter at 5.398. Rho Herculis is about 390 light-years away.
18. Tau Herculis (τ Herculis)
Tau Herculis is a luminous star of the spectral class B5IV. It has an apparent magnitude of 3.89 and radiates at a luminosity about 700 times that of the Sun. Its mass equates to 4.9 solar masses. This star is traditionally called Rukbalgethi Shemali. This name means “the northern knee” of Hercules.
A meteor shower called Tau Herculids appears to have its origin from this star. The shower occurs around the 19th of May to June.
19. Omega Herculis (ω Herculis)
Omega Herculis is a double star with a combined apparent magnitude of about 4.58. The primary is an Ap star, which has an overabundance of some metals. It is also a variable star. This primary star is formally named Cujam, meaning “the club.” Omega Herculis is 250 light-years away from the Sun.
Planets in the Kneeler’s Constellation
Extrasolar planets are discovered to be orbiting the stars 14 Herculis, HD 164595, HD 149026, HD 154345, HD 147506, HD 155358, GSC 03089-00929, and Gliese 649, among others in the constellation of the Kneeler. Let us learn about some of them and their hypothetical visualization from NASA’s Exoplanet Catalog.
14 Herculis b
The exoplanet 14 Herculis b is a gas giant that is 59 light-years away from our planet. It orbits the star 14 Herculis in the constellation of Hercules the Kneeler. This exoplanet has a mass of 4.66 Jupiters. It completes its orbit in a period of 4.9 years.
HD 149026 b
HD 149026 b is a giant exoplanet that is made up mostly of gas. It is also called Smertrios. It orbits the star HD 149026 in the northern constellation of Hercules. HD 149026 b has a mass of 0.38 Jupiters and a radius of 0.74 x Jupiter.
TrES-3 b is an extrasolar planet that orbits the G-type star GSC 03089-00929. They are in the constellation of Hercules. It is also called Umbäässa. This planet is a gas giant with an orbital period of 1.3 days and a mass nearly twice that of Jupiter’s. It was discovered in 2007.
Deep-sky Objects in Hercules Constellation
There are lots of interesting star clusters, nebulae, and galaxies in the constellation of Hercules. Some of them are NGC 6229, NGC 6210, NGC 6166, Hercules A, Abell 2199, Arp 272, and Hercules–Corona Borealis Great Wall among many others. Their curious colors and forms are what make our night sky even more exciting!
M13 is also known as The Great Globular Cluster in Hercules. It was discovered by Edmond Halley. This globular cluster is one of the brightest of its kind. We can see it in the northern sky using small telescopes. Its brightness comes from the hundreds of thousands of stars in this cluster. Overall, M13 is 150 light-years across and is 25,000 light-years away from Earth.
M92 (NGC 6341) was discovered by Johann Elert Bode. This globular cluster is 26,000 light-years away from us. It is one of the oldest and the brighter clusters in the Milky Way galaxy. The apparent magnitude of M92 is 6.3.
Abell 39 is a planetary nebula that is about five-light years in diameter. It was formed from the expelled outer atmosphere of a star. This spherical nebula is about 7,000 light-years away in the constellation of Hercules.
Hercules Cluster of Galaxies
The Hercules Cluster of Galaxies is made up of about 200 spiral galaxies and some elliptical ones. It is also known as Abell 2151. Its spiral galaxies are rich in gas and dust that are indications of star formation. It is 500 light-years away from us.
Mythology Related to Hercules Constellation
Right from the start, Hercules was born out of Zeus’s unfaithfulness to his wife Hera, which made the queen of the gods very angry.
Hercules is the son of Zeus, the king of the gods. His mother is Alcmene, a human. One night, Zeus used his powers to take on the form of Amphitryon, Alcmene’s husband, and visited her bed.
Hercules has exceptional strength which has saved him many times since his childhood when Hera devised all kinds of plans to kill him. At birth, the demigod’s name was Alcaeus. Later on, after he visited the oracle at Delphi, his name became Herakles which means “glory of Hera.” This is the start of the many challenges he has to go through in the hands of the queen god.
The hero Hercules has grown up to be a young and successful man. He has started his own family and was happy with his wife, Megara, and their children. Hera did not like what she saw so she made Hercules mad. The hero was overcome with madness that he killed his family. When Hercules recovered from this madness, grief and sadness overwhelmed him. He could not believe what he did!
Deeply sorry for his actions, Hercules went to the Oracle of Delphi to atone for his sins. Unfortunately, Hera also has her influence on the Oracle. Hercules was told that he can be forgiven for what he did by serving King Eurystheus, who is also his cousin. The king originally devised ten labours. But when Hercules completed them, Eurystheus added two more to make Hercules’s life more difficult.
The Twelve Labours of Hercules
1. Slaying Nemean Lion
The Nemean Lion was terrorizing the people of Nemea. Slaying it is next to impossible because no weapon pierces through its skin. Hercules made a plan to trap the lion in its cave. He blocked the other entrance so it would have no chance of escaping. When he entered the cave, he used a club to stun it and later on slew it using his bare hands through strangling.
Later on, Hercules skinned the Nemean Lion using its claws. The hero then wore the lion’s pelt.
2. Slaying Lernaean Hydra
The Lernaean Hydra was a nine-headed monster living in a swamp. Hercules had to think of a strategy to slay this monster because when one of its heads was cut, another two would spring from it! Good thing his cousin Iolaus helped him. Hercules cut off the heads which were seared by Iolaus so no new ones would grow. He dipped his arrows in the poisonous blood which he would use in his other conquests.
3. Capturing the Ceryneian Hind
The Ceryneian Hind was very difficult to catch. It took Hercules about a year to capture it. In addition to this, it is owned by the goddess Artemis. The goddess understood the labours Hercules need to fulfill. The hero then presented it to Eurystheus.
4. Capturing the Erymanthian Boar
The Erymanthian Boar was a big and wild boar with foaming jaws. It was challenging for Hercules to catch it. But still, he persisted and brought it back to Mycenae. It is also in this labour where Hercules met the Centaurs.
5. Cleaning the Augean stables in a one day
King Augeas has a large herd of cattle. Aside from the great number of animals, it was said that their feces contain poison. Even though it seemed impossible to finish everything in just a single day, Hercules had a bright idea. He dug ditches in the stables and diverted the flow of rivers Peneios and Alpheios into the stable to clean it.
6. Slaying the Stymphalian Birds
The Stymphalian Birds were unsatiable man-eating creatures. Athena saw that Hercules needed help so he gave him a rattle to scare off the birds. When they did fly, he shot them and brought some back to Eurystheus as proof that finished the labour.
7. Capturing the Cretan Bull
The Cretan Bull, father of Minotaur, was readily given by King Minos to Heracles. It serves no purpose to him anymore. It had been causing trouble on the crops in Crete. Hercules captured it and brought it back to Eurystheus.
8. Bringing Back the Mares of Diomedes
The mares of King Diomedes were no ordinary horses. Diomedes fed them human flesh so they were dangerous. Hercules was able to do this labour by feeding Diomedes to his mares.
9. Getting the Girdle of Hippolyta
Hippolyta was the queen of the Amazon. Hercules was initially welcomed by the Amazons but Hera told them that the hero’s plan is really to attack them. There are different versions of the story. The first one was that a fight broke and that killed Hippolyta. Another one was the girdle was given as a ransom because Hercules kidnapped Hippolyta’s sister.
10. Obtaining the Cattle of Geryon
Geryon was a giant. The herd was guarded by his dog and herdsman. He fought with them and had the cattle by himself. Hera intervened again by stinging them. The cattle scattered. The next challenge is to bring them all together as the labor will only be counted if they are complete. Hercules still succeeded in herding them.
The labours were supposed to be complete after the tenth one but Eurystheus added two more. He said that some labours did not count because Hercules received help in doing them.
By this time, he had already succeeded in obtaining the cattle of Geryon and was bringing it back to Eurystheus. Unfortunately, Hercules got into a battle with the giants Albion and Bergion (Dercynus). Seeing that defeating the giants is beyond his ability, Hercules kneeled and prayed to Zeus for guidance. When he succeeded, he continued to his next labours.
11. Stealing the Hesperides’ Golden Apples
Hercules previously helped Prometheus, so he asked his titan brother Atlas in stealing the fruits. This was great since the apples were protected by the dragon Ladon. Atlas tricked Hercules but the hero managed to succeed in the task.
In the night sky, the constellation of Draco at the feet of Hercules was said to be the dragon Ladon.
12. Capturing Cerberus
Cerberus was the three-headed dog of the underworld. Eurystheus thought that the last labour would be impossible to accomplish. But still, many adventures after, Hades allowed Hercules to take Cerberus as long as the hero did not hurt it. Hercules brought it to Mycenae which made Eurystheus afraid.
When Hercules died, his father Zeus placed him in the sky as a constellation. As we can see, the constellation of Hercules is also known as “the Kneeler.” It was the same position Hercules had when he prayed to Zeus after the tenth labour.