Hercules Globular Cluster (M 13)

The magnificent globular cluster Messier 13, also known as the Great Hercules Cluster, is the brightest globular cluster in the northern sky and one of the most spectacular stellar systems visible from Earth. Located in the constellation Hercules, it can be glimpsed with the naked eye under very dark skies as a faint, hazy patch of light. Through telescopes, however, it resolves into a dense, tightly packed cluster of stars.

Messier 13 lies at a distance of 7.4 kiloparsecs (about 24000 light-years) and spans around 50 parsecs in diameter. It contains several hundred thousand gravitationally bound stars, many of which are among the oldest in our galaxy, with ages estimated at 11-12 billion years. These stars formed early in the history of the Milky Way and are typically low in heavy elements compared with younger stellar populations.

Like other globular clusters orbiting the Milky Way’s halo, Messier 13 follows a long, elliptical path around the galaxy. Over billions of years it has remained gravitationally bound despite tidal forces from the galactic disk.

This image was captured from Sternenberg, Canton of Zurich (Switzerland) using a Celestron C14 Schmidt-Cassegrain reflector telescope. With its 256 mm apperture and ~3.9 m focal length, the instrument provides the resolution and light-gathering power needed to resolve the outer regions of the cluster into countless individual stars while still preserving the intense glow of its densely populated core.
 
Joachim Stadel and Aurel Schneider 2025