Scientists don't know the true nature of dark matter. They only know that it neither absorbs nor emits electromagnetic radiation.
It's also believed that there is so much dust, gas and dark matter near the center of the Milky Way that it forms a bulge. This material is so thick that even powerful telescopes can't see all the way through it. Scientists also believe that there is a black hole at the center of the galaxy around which this material revolves. It's billions of times more massive than the sun and continues to grow as it ingests more and more material, including whole stars.
The outer edges of the Milky Way have an envelope of gas and groupings of stars known as globular clusters. Very old stars also exist on the fringes of the galaxy. The oldest one is believed to be not much older than the universe itself.
Most stars in the Milky Way are red dwarfs. These are small, cool stars that scientists believe might be capable of supporting life on some of the planets that orbit them.Learn more about Stellar Astronomy