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Hercules

The name immediately brings to mind visions of extraordinary strength, courage and bravery. He is the most famous mythological hero of ancient Greek legends. The Romans adopted this hero from the Greeks and changed his name from Heracles to our more familiar name Hercules. He was the son of the god Zeus (the Roman name is Jupiter) and his mother was Alcmene, a mortal woman. This made him a demigod (half man-half god). The ancient Greeks celebrated him as both a god and a hero. He survived the “Twelve Labours” and then sailed with Jason and the Argonauts on their quest for the Golden Fleece. His first “labour” was to slay the Nemean lion whose hide was impervious to arrows and weapons. Hercules choked the beast to death after he had used his club to subdue it. After killing the beast he skinned the lion with its own claws. He then used the hide as an impenetrable shield draped over him like a cloak with the lions’ skull as his helmet. This is just one of the many incredible stories told throughout Grecian history about Heracles.

Given this history you might think the constellation Hercules is one of the biggest and most easily seen in the night sky. This is far from the truth. The central portion or body of this hero is a trapezoid with his arms and legs extending from each corner. The Keystone is the astronomical name given to this trapezoid. It is clearly defined in the sky when you locate this constellation.
Now let us begin a slightly difficult journey through the night ‘skyway’ finding our destination the Great HERCULES Supercluster or M 13. Let’s start at URSA MAJORs’ tail. This should be a familiar place.

Now move along the tail in an imaginary arc until you reach  Arcturus  a red giant and the brightest star of BOOTES.  Incidentally, only one other star is brighter at night than this one and it has already set (Siruis of CANIS MAJOR). I now need you to find the next brightest star Vega in the constellation LYRA. After you find Vega draw an imaginary line from it to Arcturus. This line will pass through the Keystone and come very close to M 13. M 13 is a globular cluster containing nearly a million stars. This is the most spectacular globular cluster in the northern celestial sphere. The largest globular cluster seen from earth is Alpha Centauri and  the second largest is M 22 but both are located in the southern celestial sphere. They never rise far above the horizon when seen from the northern hemisphere but the great supercluster M13 can be seen high in the night sky during mid July. The unaided eye can pick it out in a dark location with good atmospheric conditions. The beauty of this object is unbelievable when seen through a medium to large telescope. This object is 23,000 light years from earth and has a magnitude of 5.7.

Another fine globular cluster located in the HERCULES constellation that is often overlooked is M92. This cluster looks quite different from M 13 mostly due to its concentrated core. Finding this one is not as easy as the other. I move down or over to the left of  M13 to the corner star in the Keystone depending on the time I’m viewing. After finding that star I draw another imaginary line from this star through his torso and on to M 92 not too far removed from his body.
There is a variable star, alpha herculis, in HERCULES. It is the last star at the end of his club held in his left hand. This is located close to the boundary of OPHIUCHUS, the serpent handler. Alpha herculis is reddish-orange in color and its magnitude varies between +3 and +4 over a cycle of 50 to 130 days. In addition there are two double stars and a planetary nebulae NGC 6210 (bluish in color) in Hercules. Since 1996 many exoplanets have been discovered orbiting eleven stars of this constellation.

M 13 is a great starting and ending point in the summer night sky. I look forward to gazing upon this grand star cluster with various optical aids. I never tire returning to see it several times during the same evening. This object gives you the opportunity to test your visual acuity and various eyepieces as the cluster moves across the sky from thicker atmospheric layers on the horizon to the thinnest layer at the zenith. Enjoy the night sky and happy meteor shower trails to you.

Category: Other Members