NGC 6520 is an open star cluster located about 5,500 light years away towards the constellation Sagittarius. It is about 10 light years across. The bright blue stars are only a few million years old, much younger than our Sun.
Blocking the light of NGC 6520 is Barnard 86, an absorption nebula and molecular cloud. It contains is filled with thick dust that obscures the star cluster. Surrounding the cluster and nebula in this image is part of the dense starscape of our own Milky Way.
Image and information from NASA.