Hercules Constellation

Mythology

Hercules, the great hero of Greek mythology (Heracles in Greek), is one of the largest constellations, covering 1225 square degrees, though it contains no first-magnitude stars. The figure is depicted kneeling on one knee with a club raised, representing some moment of his labours. Heracles was the son of Zeus and the mortal woman Alcmene; the goddess Hera, Zeus's jealous wife, persecuted him throughout his life. He was tasked with performing Twelve Labours to atone for a crime committed during a fit of madness sent by Hera: slaying the Nemean Lion, the Lernaean Hydra, the Erymanthian Boar, the Cerynitian Hind, the Stymphalian Birds, the Augean Stables cleaning, the Cretan Bull, the Mares of Diomedes, the Girdle of Hippolyta, the Cattle of Geryon, the Apples of the Hesperides, and the Capture of Cerberus. The kneeling figure in the sky was identified with this kneeling Heracles by the time of Eratosthenes. The Great Hercules Cluster (Messier 13), a spherical collection of approximately 300,000 stars about 25,100 light-years from Earth, is one of the finest globular clusters visible from northern latitudes and is easily resolved in a small telescope.

Sources: Apollodorus Bibliotheca 2.4-7; Aratus Phaenomena 63-70; Hyginus Astronomica 2.6.

Overview

Hercules is one of the 88 constellations formally recognised by the International Astronomical Union (IAU). It occupies 1225 square degrees of sky in the northern hemisphere sky, best visible at latitudes between +90 and -60 degrees in June. The constellation belongs to the Hercules family of constellations. Its Latin genitive is Herculis, the form used when naming stars within the constellation — for example, the brightest star Kornephoros may appear in catalogues as Alpha Herculis or similar. The IAU standardised the boundaries of all 88 constellations in 1930 under the direction of Eugène Delporte, using straight lines of right ascension and declination to eliminate the ambiguities of earlier variable-boundary systems.

Notable stars

The brightest star in Hercules is Kornephoros. Individual stars within Hercules are conventionally named using Bayer designation — Greek letters followed by the Latin genitive of the constellation name (Herculis) — introduced by Johann Bayer in his 1603 star atlas Uranometria. Flamsteed numbers (numeric designators followed by Hercules) were added by John Flamsteed in his 1712 catalogue. Variable stars, double stars, and deep-sky objects within the Hercules boundary are catalogued by the IAU with the abbreviation Her.

History and mythology

The figure of Hercules appears in the classical astronomical tradition. Ptolemy included this constellation in the Almagest (c. 150 CE), the definitive ancient catalogue of 48 constellations, which formed the foundation for Islamic, medieval European, and Renaissance astronomy. The constellation's figure and mythology were transmitted through works such as Aratus's Phaenomena, Eratosthenes's Catasterismi, and Hyginus's Astronomica. See the Mythology section above for the full narrative.