M13: The Great Globular Cluster in Hercules . ... Credit Copyright: Yuugi Kitahara Explanation: M13 is one of the most prominent and best known globular clusters. ... M13 is a colossal home to over 100,000 stars, spans over 150 light years across, lies over 20,000 light years distant, and is over 12 billion years old. At the 1974 dedication of Arecibo Observatory , a radio message about Earth was sent in the direction of M13 . ... NASA Web Site Statements, Warnings, and Disclaimers . ...