Deep Sky

Constellation: Sagittarius
Elliptical gobular cluster
This bad boy is one of the brightest gobular clusters in the sky, unfortunately it is located in the southerly declination and doesnt rise high in the sky therefore it appears less impressive than other globular clusters.  It is some 32' on the sky which comes out to almost 9 light-years diameter.  There are some 32 variable stars located in M22, additionally it is unusual in that it is only one of four globular clusters to contain a planetary nebula.  (No we cant see it in this image.)
It was discovered by Abraham Lhle in 1665, and our Messier catalogued it in June 1764. Harlow Shapely, in 1930 really got into studying M22.  He came up with approx 70,000 metal-poor stars in the dense core.  What is most interesting is that new information on M22 and black holes, from our own VLA.  

10 images
5 sec
date: 9-15-12