M13 in Hercules is one of the finest globular clusters in the northern hemisphere, containing several hundred thousand stars packed into a sphere roughly 145 light-years across at a distance of about 25,100 light-years. Discovered by Edmond Halley in 1714, it is estimated to be around 11.65 billion years old — nearly as old as the universe itself. In 1974 the Arecibo message — humanity’s first deliberate radio transmission to potential extraterrestrial intelligence — was directed toward M13.