Mighty Hero, Dim Stars

One of the greatest heroes from Greek mythology is Hercules.  The tales of his "Twelve Labors" are among the classics of ancient literature.  Yet the constellation of Hercules is surprisingly dim, and is almost invisible under light polluted skies.

Fortunately, Hercules lies almost equidistant between the stars Vega (in Lyra the Harp) and Arcturus (in Boötes the Herdsman).  

Hercules doesn't really look much like a Greek warrior, or even a human being for that matter.  But Hercules is easy to recognize if you find the 4 stars that form a rough trapezoid shape.  This is an asterism known as The Keystone, because it looks like the old style stones that completed the archway above a door in a building.  

Looking between the two stars of the side of the trapezoid nearest Arcturus you can spot M13, the Great Globular Cluster of Hercules.  This globular cluster is one of the best examples of these far away, ancient spheres of stars. 

Like M4 in Scorpius, M13 is one of the globular clusters that sit in a halo outside the plane of our galaxy.  It lies 25,000 light years away, and yet under dark skies it can just barely be seen with the unaided eye.

Created by the author using Stellarium