Click here for a printable version of this page.

Hercules

(HER-kyou-leez)

The Mighty Hero, Heracles

Famed for his strength and for his Twelve Labors, he was known as Heracles, the mightiest hero of them all, to the Greeks, but better known today by his Latin (Roman) name of Hercules.

Visibility: At 8:00 p.m. Standard Time (9:00 p.m. Daylight Saving) Hercules is low in the east in early April. It continues to rise through the year until it nears the zenith in July and August. Hercules then begins to lower in the west, setting into the twilight by October.

What to look for: The constellation Hercules is made of relatively faint stars. It is most easily recognized by the trapezoidal asterism (a commonly known grouping of stars that is not an official constellation) known as the Keystone. We see the hero upside down in the sky. His head, the star Ras Algethi (Alpha Herculis), is next to the star Ras Alhague (Alpha Ophiuchi), the head of Ophiuchus, the Serpent Holder, to the south. Hercules is kneeling, his hands upraised. One foot rests on the head of Draco, the Dragon, to the north. To the west is Corona Borealis, the Northern Crown, and to the east is Lyra, the Lyre, with its very bright star Vega (Alpha Lyrae).

A third of the way between the northwest corner of the Keystone, Zeta Herculis, and the southwest corner, Eta Herculis, is M13, the Great Globular Cluster in Hercules, hundreds of thousands of stars packed into a ball a few tens of light-years across. Just visible to the naked eye in a dark sky, through the telescope M13 looks like a spoonful of diamond dust on black velvet. Only slightly fainter is M92 to the northeast of M13, another globular cluster often referred to as The Lesser Hercules Cluster.

Mythology: Heracles' father was Zeus (Jupiter to the Romans), king of the Olympian Gods. His mother was Alcmene, granddaughter of Perseus (another son of Zeus) and Andromeda. The young hero was originally named Alcides, after his mother. Hera (Juno), Queen of the Gods, was enraged over yet another example of her husband Zeus' infidelity. Realizing the boy was immortal, Hera vowed to make his life miserable, and opposed him throughout his career.

Hera cursed Alcides with a fit of madness in which he killed his own children. When he came to his senses, he went to the Oracle of Delphi, who said the sorrowful hero could atone for his dreadful deed by performing ten labors at the service of Euristheus, the cowardly king of Mycenae.

The Oracle also gave the hero a new name, Heracles, "Hera's Glory," in an attempt to placate his irate stepmother. The ploy was unsuccessful, and she continued to throw obstacles in his path. Hera even managed to have two of Heracles' successful labors disallowed, thus raising the number of tasks to twelve.

The earliest Greeks did not identify this constellation with their greatest hero. It was only known as Engonasin, the Kneeler, an unglorified toiler resting from labors equally unknown. The figure was created by the Sumerians and their neighbors around 3000 BC, who pictured it as Marduk, the king of their gods. Viewed on a summer evening during that epoch, he knelt in the north, his head nearly touching Ophiuchus' head as the latter figure stood in the south.

By the time the Greeks inherited the ancient constellations from the Babylonians, the sky had shifted due to precession (precession is the slow change in the direction that the Earth's axis of rotation points; one complete cycle of precession takes about 26,000 years to complete), and the Kneeler now passed overhead, his head dangling downward to the south. Only when some twelve thousand years have passed will the sky shift far enough to return the Kneeler to an upright position.

Eratosthenes, head librarian at the Museum of Alexandria and the first person to measure the circumference of the Earth, first identified the Kneeler as Hercules in the Third Century BC, and it was not until the Fifteenth Century AD that star maps consistently used the present name.