Globular Cluster in the Constellation Hercules
Messier 13 (M13, NGC 6205), also called the 'Great globular cluster in Hercules', is one of the most prominent and best known globulars of the Northern celestial hemisphere. At its distance of 25,100 light years, its angular diameter of 20' corresponds to a linear diameter of 145 light years . It contains several hundred thousand stars. Towards its center, stars are about 500 times more concentrated than in the solar neighborhood. The age of M13 has been determined by Sandage as 24 billion years and by Arp as 17 billion years around 1960; Arp later (in 1962) revised his value to 14 billion years (taken from Kenneth Glyn Jones).
Also visible in the upper left corner of the
field are the two faint, distant galaxies NGC 6207 (the brighter galaxy of the
two), and IC 4617. NGC 6207 lies at a distance from Earth of approximately
39 million light-years. IC 4617 lies at a staggering distance of 490
million light years from Earth. (Text info courtesy of SEDS).