M23, NGC 6494

The irregular star cluster M23, or NGC6494, is a bright, large, rich, rather attractive, cluster in the constellation Sagittarius. Some 2200 light-years away, M23 has a diameter of about 20 light-years (around 30 minutes of arc): this picture is 35 minutes across. M23 is over 200 million years old. As M23 is in the galactic plane, the background stars are increasingly reddened by dust absorption, and this image has several black areas where any distant stars are hidden by the thick dust. The bright star to the NW (upper right) is a foreground object. This true-color picture was created from six images taken in the BVR pass-bands at the Burrell Schmidt telescope of Case Western Reserve University's Warner and Swasey Observatory. The Burrell Schmidt is located on Kitt Peak, near Tucson, Arizona. The images were taken in July 1995 during the Research Experiences for Undergraduates (REU) program operated at the Kitt Peak National Observatory and supported by the National Science Foundation.