Audio Guide：

Our galaxy is a barred spiral galaxy. It looks like a thin sunny-side-up egg from the side. With a diameter of about 100,000 light-years, its thickness is only a few thousand light-years. Viewed from the front, spiral arms can be clearly seen. Most visible matter in the Milky Way is concentrated on the plane called the disc. This is also the region where stars are born. At the center of the disc is a slightly raised area known as the galactic bulge. At the innermost center is the nuclear bulge. Scientists speculate that a super-massive black hole exists at the Galactic Center. The Milky Way is surround by the spherical galactic halo, where most old stars and globular clusters are found.