Approximately 5000 light-years distant, M11 is one of the richest and most compact open clusters, with nearly 3000 stars concentrated in a region only twenty light-years across, many of which are upper Main Sequence blue giants, or more highly evolved yellow and red giants. As a result, an observer in the center of the cluster would see several hundred first magnitude stars scattered around the sky. Given the presence of Main Sequence stars up to spectral class B8, the age of the cluster is estimated at 250 million years, or only about 5% the age of our solar system.
     As is the case with many of the objects in Messier's catalog, M11 was first noticed (as a fuzzy patch in the sky) nearly a century earlier, in this case by German astronomer Gottfried Kirch, in 1681. William Derham was probably the first to see that it consisted of a cloud of faint stars, in 1733. Messier added it to his catalog in 1764. (Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT, apod0301220; Copyright CFHT)