The Milky Way is a spiral galaxy in which most of recorded history takes place. The name "The Milky Way" comes from Earth; the galaxy is also known as the "home galaxy." (TNG video game: Echoes from the Past)
The Milky Way is approximately thirteen billion years old and 100,000 light-years across, 15,000 light-years deep at the galactic core and contains approximately 200 billion stars which orbit the galactic core over a period of around 220 million years. Somewhat unusually, the Galaxy is enveloped in an energy field known as the galactic barrier. A similar field, the Great Barrier, encloses much of the Galactic Core. Both fields were created by the Q Continuum to protect the galaxy from, respectively, 0 and The One. (TNG novel: Q-Strike) These fields had the effect of making the Milky Way a safe haven from both natural phenomena and any malicious entities, such as the beings described above. Several races, such as the Caeliar, were unwilling to leave the Milky Way, as they would then lose the protection offered by the Great and Galactic Barriers.
In addition to the main body of the Milky Way, the galaxy has a number of smaller companion bodies, most notably the smaller and larger Magellanic Clouds. The galaxy is also in the process of absorbing a dwarf Galaxy SagDEG. The Milky Way's nearest large neighbor is the Andromeda Galaxy, some 2.2 million light-years away.
The Galaxy is naturally subdivided into a number of "arms", with the Federation and its neighbors mostly occupying the Orion Arm. However, for the sake of standardized navigation the Federation and most other galactic powers divide the Galaxy into four equal segments: the Quadrants.
Given the huge size of the Galaxy and the limited velocities available at warp speed a number of races use networks of subspace pathways to navigate the galaxy. Some are natural such as those formally controlled by the Vaadwaur, whereas others are artificial constructs such as the Borg Transwarp, Iconian Gateway and the Caeliar Subspace Tunnel networks or the Bajoran wormhole. (ST reference: Star Charts)
(radiating from the center clockwise)
- 3 KPC Arm (the Shapley Center)
- Norma Arm
- Crux Arm
- Carina Arm
- Orion Arm
- Perseus Arm
- Outer Arm
- Scutum Arm
- Sagittarius Arm