The stars are not alone. 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). The ISM is not uniform and shows patchiness even near our Sun.

Why did the Boomerang Nebula form? The symmetric cloud dubbed the Boomerang appears to have been created by a high-speed wind of gas and dust blowing from an aging central star at speeds of nearly 600,000 kilometers per hour.

In many cosmic environments, when material falls toward a black hole energy is produced as some of the matter is blasted back out in jets. In fact, such black hole "engines" appear to be the most efficient in the Universe, at least on a galactic scale.