Hercules and His Lesson
The constellation Hercules rises in the East in May and June about the time that our sky is getting dark enough to see the stars. It will be visible in the night sky from now through the summer and fall. However, while the hero for whom it is named was a brilliant hunter, his constellation is not distinguished by any brilliant stars.
Image: Legg Middle School, Coldwater, MI
Hercules is located about halfway between Vega and Arcturus and is usually thought of crouching upside down. He could be looking down toward the North Star. The center is often described as a butterfl y, using six of the brighter stars to outline the insect. Four of the most northern stars of the butterfl y mark the “Keystone” where the most interesting object of the constellation, the Great Globular Star Cluster, is found. This cluster, also identifi ed as M13, lies on a line between the western two stars of the Keystone. It was noted fi rst by Edmund Halley in 1715; Charles
Messier who catalogued it about 50 years later thought it was only a fuzzy cloud. With even as small as a 4” telescope, today we can get an idea of the swarm of its million sparkling points. M13 is measured at about 25,000 light years (ly) away from Earth; the diameter of its core is about 300 ly. It is made up of about a million stars rotating around a gravitational center. You can maybe begin to imagine the size by this comparison: In the densest part of the core, if the individual stars were the size of grains of salt, they would be separated from each other by several miles.
Globular clusters are typically balls that rotate around themselves and are held together by gravitational pull. They evolved about 10 billion years ago, evidenced in the fact that they are metal poor. That is, they were formed before gasses in the universe had fused creating the heavy metallic elements.
None of the stars in Hercules is more than third magnitude. But in spite of its somewhat nondescript character, Hercules apparently was one of the fi rst constellations to be named. And it was also named for a hero or a god in the languages other than Greek. The Phoenicians called it the sea god Melkarth. Among the Babylonians it was either the hunter Nimrod, the hero of the Flood story Gilgamesh, or the sea god Izhdubar. Greek writers sometimes called it “the Kneeler,” and when it was used as an image on coins, Hercules was shown on Greek coins kneeling to string his bow, or wearing the skin of the Nemean lion that he had overcome as one of his twelve labors.
In the story of Hercules’ encounter with Atlas, it was the hero’s cleverness pitted against the physical strength of the giant who was holding up the sky. Hercules agreed to carry the sky briefl y while Atlas fetched the Golden Apples for him (another of his labors). Of course Atlas wasn’t eager to resume the load of the sky, but Hercules tricked him by agreeing to continue to hold that burden if Atlas would take it just a moment while he shook himself and shifted the lion skin to protect his shoulders. The shaking dislodged several stars, and Atlas was so startled that he didn’t notice Hercules escaping. Hercules got even with him when he joined the immortals in the sky because his weight added that much more for Atlas to bear.
Could it be that meteor showers, which we think are residue from a comet’s trail, really mean that Atlas has managed get someone else to hold up the sky momentarily and is knocking a few stars loose by shaking his shoulders?