M23

M23 lies about 2,150 light years from Earth and contains about 150 stars. Spanning about 27 arc minutes, this cluster is between 15 and 20 light years in diameter. At an age of 220 to 300 million years, M23 is one of the older open clusters found in the Milky Way. Since it lies only a few degrees from Mu Sagittarii, it is difficult to determine which stars being seen visually are part of the cluster and which are background stars of our galaxy.

The magnitude 6.5 star below and left of center is a foreground star and not part of the cluster.

Image taken late August or early Sept., 2006.