Most of the constellations in the sky are located and viewed depending upon their position and hemisphere. Amateur astronomers find it very exciting to view heavenly bodies through telescopes by themselves. However, they stated a fact that unlike the other constellations, the location of Hercules differs widely, depending on the hemisphere of the earth. Located in the northern sky, Hercules is the fifth largest constellation in the sky. Traditionally, it is depicted as a prominent asterism, the keystone that marks his torso as he stands victoriously on Draco’s head. The constellation was first catalogued by the Greek astronomer Ptolemy in the 2nd century. It is the name of a mythological character meaning ‘the glory of Hera’. It belongs to the Hercules family of constellations and is best visible in the month of July at 9 pm.
Some of the notable stars in this constellation are:
- ASTERISM (The Keystone): Asterism is formed by four bright stars in the constellation namely Pi, Eta, Zeta and Epsilon Herculis. It also represents Hercules’ torso.
- Kornephoros (Beta Herculis): It is the brightest star in this constellation. With a visual magnitude of about 2.81, it is about 139 light years away. The primary star in this system is basically a giant, which is three times as massive as the sun.
- Z Herculis (Zeta Herculis): It is basically a multiple star in this constellation. It has a combined magnitude of 2.81 and is about 35 light years away from the earth. It is the brightest of the four stars which form the Asterism. The primary star in this system is basically a sub giant star, which is six times brighter than the sun.
- Sarin (Delta Herculis): It is also a star system in this constellation which is composed of between 2 to 5 stars. It has a visual magnitude of about 3.126 and is about 75.1 light years away from the sun.
- π Herculis (Pi Herculis): It is another star in this constellation which forms the Asterism. It is a bright giant star. With a visual magnitude of 3.15, it is about 377 light years away from the solar system. Pi Herculis is about 1,330 times brighter than the sun.
- Rasalgethi (Ras Algethi) a Herculis (Alpha Herculis): It is a multiple star system in this constellation. Alpha–1 has a visual magnitude of 2.1937, whereas Alpha–2 has a visual magnitude of 5.4. This multiple star system is about 360 light years away from the earth. The primary star in this system is a bright red giant. Alpha–2 is basically a binary star system, composed of a yellow–white dwarf and a yellow giant.
- Marfak Al Jathih Al Aisr (Mu Herculis): It is also a star system in this constellation and has a primary component. With a visual magnitude of 3.417, it is about 27.11 light years away from the earth. The secondary component is a binary star, with an orbital period of 43.2 years.
- Sophian (Eta Herculis): Sophian is a main sequence star in this constellation. It has a visual magnitude of about 3.487 and is about 112 light years away. Sophian is 50 times brighter than the sun and is believed to be a billion years old. Eta Herculis is a double star, with a companion that has a visual magnitude of 12.5.
- ξ Herculis–(Xi Herculis): Xi Herculis has a visual magnitude of 3.70 and is about 160 light years away from the solar system. Xi Herculis is about 62 times brighter than the sun.
- y Herculis (Gamma Herculis): It is a spectroscopic binary system in this constellation. With a visual magnitude of 3.75, it is about 193 light years away. Its primary star is a giant and a rapid rotator with a projected rotational velocity of about 135 km/s.
- i Herculis (Iota Herculis): It is a sub giant star in this constellation, has a visual magnitude of 3.7497 and is about 455 light years away from the sun. Iota Herculis is about 2,500 times brighter than the sun.
- 109 Herculis: It is an orange giant with a visual magnitude of 3.84 and is about 119 light years away from the sun.
The other notable stars in this constellation are Atia (103 Herculis), Rukbalgethi Genubi (Theta Herculis), Rukbalgethi Shemali (Tau Herculis), Cujam (Epsilon Herculis), Maasym (Lambda Herculis), V Herculis (Nu Herculis), Kajam (Omega Herculis), Marfik (Kappa Herculis), 89 Herculis, 14 Herculis, Gliese 651 (HD 154345), HD 155358, HD 147506, Gliese 623, Gliese 649, Gliese 661, GSC 02620–00648 A and GSC 03089–00929.
Some of the deep sky objects of Hercules include:
- The Great Globular Cluster–Messier 13: Messier 13 is also known as the Great Globular Cluster as it consists of about 300,000 stars located in Hercules. The cluster has a visual magnitude of 5.8 and is about 22,200 light years away. The brightest star in this cluster is a variable star with a visual magnitude of 11.95. Under good conditions, it can be easily seen with small telescopes.
- Messier 92 (NGC 6341): It is a globular cluster in this constellation. Messier 92 is relatively bright, has a visual magnitude of 6.3 and is about 26,700 light years away from the sun. In the Milky Way, it is one of the oldest clusters. The estimated age of Messier 92 is believed to be 14.2 billion years.
- Hercules Cluster (Abell 2151): It is a galaxy cluster in this constellation, about 500 million light years away from the solar system. Hercules Cluster also comprises of about 200 galaxies.
- Abell 39: It is basically a planetary nebula in this constellation and is about 6,800 light years away. The central star in it has magnitude of 15.5 while the nebula has a magnitude of about 13.7.
- Abell 2199: It is basically a cluster of galaxies in this constellation. It contains over 290 galaxies.
- Arp 272 (NGC 6050 and IC 1179): Arp 272 is basically a name termed for a pair of colliding spiral galaxies in this constellation. NGC 6050 and IC 1179 are about 450 million light years away from the earth.
- NGC 6166: NGC 6166 is a giant elliptical galaxy comprising a large halo of stars in this constellation. It is about 490 million light years away. It also has a super massive black hole at its core. This giant elliptical galaxy has a visual magnitude of about 12.78.
- Hercules A: It is an active galaxy in this constellation which appears like an elliptical galaxy. Hercules A is about 2,100 million light years away from the earth.
- NGC 6210: It is a planetary nebula in this constellation and is formed when a star similar to the sun, during the end of its life, eject multiple shells of material into the space leaving behind a hot, white dwarf at the core of a newly formed planetary nebula. It is about 6,500 light years away from the earth.
Hercules lies in the third quadrant of the northern hemisphere and can be seen at latitudes between +90° and -50°.
It occupies an area of 1,225 square degrees, making it the fifth largest constellation in the sky.
According to the Greek mythology, Hercules is a hero whose adventures have provided the basis for several other constellations. Hercules is represented as an illegitimate child of Zeus, the King of Gods. In order to bed her mother Alcmene, Zeus disguised himself as Alcmene’s husband. As a result, she gave birth to twins, one of which was fathered by Zeus while the other by her husband. Hercules’ stepmother, Hera taunted him throughout his life, which eventually led to Hercules killing his own children in a fit of rage. He was ordered to carry out twelve labours as a way of atoning for his act of madness, which he eventually completed. Due to this courage and bravery shown by him throughout his life, Hercules became a god upon his death.
Hercules neighbours constellations like Aquila, Bootes, Corona Borealis, Draco, Lyra, Ophiuchus, Sagitta, Serpens Caput and Vulpecula.
