... M78 is visible with a small telescope toward the constellation of Orion. The dust not only absorbs light, but also reflects the light of several bright blue stars that formed recently in the nebula. ... In the disk of our Milky Way Galaxy about 10 percent of visible matter is in the form of gas, called the interstellar medium (ISM). ... Cen A is a giant elliptical galaxy a mere 10 million light-years distant with a central jumble of stars, dust, and gas that probably hides a massive black hole. ...