... Symbiotic Star Bubbles . ... The two stars at the center of this nebula are very different. One is a white dwarf star with a mass similar to our Sun but with a radius as small as our Earth. ... The Witch Head Nebula . ... The Pleiades star cluster is one of the jewels of the northern sky. ... Reflections on NGC 6188 . ... Located 4000 light years away in the disk of our Galaxy, NGC 6188 is home to the Ara OB1 association, a group of bright young stars whose nucleus forms the open cluster NGC 6193. ...