Milky Way Galaxy
From Hidden Frontier
The Milky Way Galaxy is a large barred spiral galaxy that is approximately 100,000 light years in diameter, and contains over 400 billion stars.
The galaxy is composed of three major parts: the core, which contains a supermassive black hole called Sagittarius A, the disc, which is the ring of stars and interstellar dust that gives the galaxy its spiral shape, and the halo, which includes many older stars orbiting the core, but outside the disc, of which most are concentrated in massive globular clusters.
The Milky Way's disc is surrounded by a massive barrier of unknown origin, which prevents most travel into and out of the galaxy.
The core is also surrounded by a similar force field called the "Great Barrier", which is very difficult to penetrate.