Star Constellation Facts: Hercules

Star Constellation Facts: Hercules

Hercules is the 5th biggest constellation, and contains 22 stars which span an impressive 1225 square degrees of sky. It can be seen from latitudes between +90° and -50° and is visible from both hemispheres with the best viewing times for the Northern Hemisphere between April and November, and for the Southern Hemisphere between June and September.

Hercules is bordered by the constellations Aquila, Boötes, Corona Borealis, Draco, Lyra, Ophiuchus, Sagitta, Serpens Caput, and Vulpecula.


The origin of the constellation is widely assumed to have its roots in Sumerian times, and is associated with the hero Gilgamesh, a mythical hero famed for his great strength. Similarly, the constellation according to Greek mythology is associated with perhaps the greatest hero of them all, Heracles, the son of Zeus and Alcmene, who was a mere mortal. However, soon after his birth, Zeus placed him at the breast of the sleeping Hera, and having suckled the milk of a goddess, Heracles became a demi-god, and thus immortal.

Understandably, Hera was somewhat upset with both Zeus’s philandering, and the fact that she was tricked into suckling the child of a mortal woman, and since she could not murder the child outright, she took a vow to make his life as difficult as was godly possible. For a start, Hera bewitched Heracles, which made him insane and as a result, he killed his wife and children. Realizing what he had done, Heracles then consulted the Oracle of Delphi, who sent him to enter the service of Eurystheus, the king of Mycenae, for a period of twelve years to atone for his crime, and it was during this period that he acquired the name “Heracles”, which translates into “The glory of Hera”.

This was also the time when he performed his famous twelve labors, but in the end he died at the hands of his wife Deianeira, who poisoned him at the instigation of Nessus, a centaur who tricked her into believing that Heracles’ blood could be turned into a potent love potion.

Star Constellation Facts: HerculesPrincipal Stars

Despite being the 5th largest constellation in the night sky, Hercules has no stars above 3 magnitude. Rasalgethi (alpha Herculis) is a variable red giant (3 to 4 mag) with a giant yellow-white companion star, while Kornephoros (Beta Herculis), is the most luminous star in Hercules, and is a binary system 139 light years away with a variable apparent magnitude (2.18 to 2.76 mag). Hercules’s torso is represented by an asterism of four stars known as the Keystone (epsilon, zeta, eta and pi Herculis), while Sarin (Delta Herculis) is 75 light years away and is twice the size our sun.

Deep Sky Objects

Messier 13 (M13, NGC 6205) also known as “The Hercules Globular Cluster” consists of approximately 300,000 stars, and is 145 light years in diameter. Being 22,200 light years distant, M13 can be seen in small telescopes, but is difficult to see without an optical aid, even under the best seeing conditions.

Messier 92 (M92, NGC 6341) is around 27,000 light years away, and is estimated to be 14.2 billion years old, which makes it one of the oldest clusters of the Milky Way galaxy, and almost as old as the universe itself.

The Hercules Cluster (Abell 2151) consists of a group of about 200 galaxies about 500 million light years away, and is part of the much larger Hercules Super Cluster (SCI 160) of galaxies.

Meteor Showers

The Tau Herculids are the sole meteor shower associated with the constellation, and is active from May 19 to June 19 with meteor counts averaging about four per hour.