Hercules, the Constellation
is almost directly overhead late in July at about 11 p.m. It lies between the easily recognizable Corona Borealis and the equally familiar Lyra; find it by looking about a third of the way from Vega toward Arcturus. Except for its central geometric trapezoid, the full star pattern is not easy to trace, although the constellation is one of the oldest identified sky figures and, in earlier forms, was known in Assyrian texts in 3000 BC.
In the land of the Euphrates, these stars were looked upon as their Sun god, Izhbudar. Like Hercules, Izhbudar was credited with unbelievable exploits, and his position in the sky shows him as he slays the dragon, Draco. In Babylonia it was Gilgamesh, also a mighty hero whose prowess in battle against the monsters paralleled those of the later Hercules. Likely the early myths gradually changed into the familiar twelve labors of Hercules.
Hercules was the son of Jupiter and the mortal Alcmene and so he was also a mortal, but with semi-divine and superhuman strength. Juno, jealous of Jupiter's many sons by mortal women, had made Hercules a slave to King Eurystheus. First, Hercules strangled the Nemean lion. The spirit of the lion was rescued by Jupiter and returned to the heavens as the constellation Leo. The second task was to destroy the Hydra. his enormous reptile had nine heads, the middle one immortal. If any of the other eight was cut off, two more regenerated in its place. Hercules solved this problem by burning the heads, except for the immortal one, which he buried under a large rock, where it presumably still lies dormant. Again, Jupiter transported the fallen beast to the skies, and Hydra can be found to the south of the Lion.
Then, Hercules was ordered to kill some horrid birds, the Stymphalides; he accomplished this with the help of his benefactor, Minerva. In the sky, near Hercules, can be found Aquila, the eagle, and Cygnus, the swan—which may represent the Stymphalian birds—as well as Sagitta, perhaps the arrow Hercules used for this exploit.
To clean the Augean stables, which housed 3000 oxen and had not been cleaned in thirty years, Hercules diverted two rivers and managed the job in just one day. Later, he fought the river-god Achelous and won the hand of the beautiful maiden Deianira. The marriage was not happy, however, and, thinking that Hercules had fallen in love with a servant girl, Deianira bewitched him and caused his death. His mortal body was transformed by Jupiter into the constellation, while his soul joined the immortals on Mount Olympus.
None of approximately 30 naked-eye stars in Hercules is very bright, but in a dark sky the four “keystone” stars form one of the most recognizable early-summer asterisms. South of this star group is a splendid, very red star, Ras Algethi (Alpha Herculis), an irregular variable binary, one of the larghest stars we know about. The brightest star in the constellation is Beta Herculis, Korneforos, the Club-bearer. This is a magnitude 2.8 spectroscopic binary with a period of 410 days. Marfik (Marfak) is Kappa Herculis, a yellow and light garnet double star that, with a number of other pretty double stars in this region, makes Hercules an interesting constellation for backyard astronomers during the summer months.
Lying on the western edge of the “keystone” the globular cluster M13 in Hercules is one of the finest in the sky for northern hemisphere observers. It is a fuzzy patch of light to the unaided eye but gives evidence to its hundred thousand or more stars when observed with a small telescope. The cluster was first pointed out by Edmund Halley in 1714, and consequently is sometimes known as Halley's Nebula, for it was at first thought to be a nebula. Messier listed it as M13. For a truly magnificent view of this celestial object be sure to arrange to see it through one of Chabot's telescopes—photographs cannot show the true wonder of such a cluster since the concentration of light at the center inevitably exceeds the contrast range that the camera can record. Conrad Jung used a 10" telescope at f/5.6 for this image of M13. Exposure was 30 minutes on hypered Konica 400 film.
Another object of interest is M92, a globular cluster, a bit smaller than M13, but worth the hunt. From M13 go 6.5° east and 6.76° north to find it.
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