Hercules appears as a kneeling man, located between Draco and Ophiuchus. His foot is on Draco's head, as if ready to slay the dragon. Lyra is to the east, and Corona Borealis is to the west. Hercules is a major constellation of the spring and summer months in the northern hemisphere.
History and Mythology
Hercules was known for his tremendous strength. He was the son of a mortal mother, Alcmene, and the god Zeus. Hera, the jealous wife of Zeus, plotted to kill the baby Hercules. She sent serpents to kill the child, but Hercules strangled the creatures. As he grew, Hercules gained great strength, until he became the strongest man in the world.
Hercules was the personal servant of Omphale, the Queen of Lydia. To win his freedom, he had to perform twelve great labors. His accomplishments were compared with the Sun's annual journey through the twelve signs of the zodiac. When he died, Hercules was taken to join the gods on Mount Olympus where he was placed in the heavens.
Notable Stars
The four upper stars in Hercules form a figure known as the "keystone". The main figure of the constellation resembles the outline of a butterfly.
Alpha Herculis has the Arabic name Ras Algethi, meaning "head of the kneeler". It is a variable red giant of spectral class M5, and varies in magnitude from 3.1 to 3.9. It is also beautiful double star, with a 5th magnitude companion. Their striking color contrast makes them appear red and green. The system is about 380 light years away and has an orbital period of 3600 years.The brightest star in Hercules is Beta Herculis, or Kornephoros, "the club bearer". It is magnitude 2.8 and is about 148 light-years away.
Third-magnitude Zeta Herculis is the second-brightest star Hercules. It is a nearby double star, only 35 light years away, with golden-yellow components of magnitude 2.9 and 5.5. These two sunlike stars orbit each other with a period of 34.5 years, appearing only 1.4 arcseconds apart. Mu Herculis is another nearby sunlike star, 27 light years away, with a pair of dim red dwarf companions.
Clusters, Nebulae, and Galaxies
The globular cluster M 13 is one of the most magnificent objects in the northern sky. At magnitude 5, it contains about 300,000 stars, and it is about 24,000 light-years away. It is visible with the naked eye, and in an 8 inch telescope M 13 resolves into thousands of stars. Famously, M 13 is the object to which the Arecibo radio telescope sent a message indicating the existence of humanity in 1974.
M 92 is a less prominent globular cluster on the north edge of Hercules. It is fainter and less rich than M 13, but its stars are more centrally concentrated than M 13's.
The 10th magnitude NGC 6210 is a planetary nebula located northeast of Kornephoros.