Exposure: L 14×300 Bin 1, RGB 14×150 Bin2
Telescope: 10″ RC
Camera: QSI 683
Distance: 25,100 Light Years
Size: 20 Arc Minutes
Cluster Type: Globular Class V
Messier 13 is a large Class V (medium star density) globular cluster in the constellation Hercules. This cluster contains over a million stars* and shows well in short exposure images. M13 is very old at 14 billion years but contains some blue straggler stars which indicate much younger stars. One theory about blue straggler stars formation says they are older stars that have merged together from gravitational interaction and as a result are hotter that the surrounding stars. Another possibility is the stripping of outer layers from the star from interaction with other stars.
*Kevin Tran UC Davis July 29, 2009 reports over a million stars
Like all globular clusters, the stars of M13 formed about the same time and are about the same age. We know this because many of the earliest stars of globular clusters were very large and had a very short lifespan. During their demise they went supernova and blew any remaining gas and dust out of the area thereby depriving the area of any materials for star formation. What is left after these first few million years is the smaller stars that fall in to the main sequence and these are what we see today. The star density in the core area is very dense. There are several hundred thousand stars within a 6 parsec area around the core. In contrast, the nearest star to our sun is 1.3 parsec away. Could you imagine what the day and night sky would look like from a star near the core of M13? It would be awesome!
[Michael Warren McCutcheon, Department of Physics, McGill University, Montreal, April 11, 2011]