Milky Way

The Orion Arm is a minor spiral arm of the Milky Way galaxy. The Solar System and therefore the Earth lies within the Orion Arm. It is also referred to by its full name, the Orion-Cygnus Arm, as well as Local Arm, Orion Bridge, Local Spur and Orion Spur.
Our Local Arm is located between the Carina-Sagittarius Arm (toward the Galactic Center) and the Perseus Arm (toward the outside Universe), the latter one of the two major arms of the Milky Way. Long thought to be a minor structure, a "spur" between the two longer adjacent arms Perseus and Carina-Sagittarius, evidence was presented in mid 2013 that it might be in fact a branch of the Perseus Arm, or possibly an independent arm segment itself.
Orion Arm | SciencePenguin.com

Properties of the Milky Way

Diameter of the Galaxy 100,000-120,000 light-years

Classification of the Galaxy SBbc

Number of stars in the Galaxy 200 billion

Mass of the Galaxy 1 trillion solar masses

Length of the central bar 25 000 light years

Distance of the Sun from the centre 26 000 light years

Thickness of the Galaxy at the Sun 2000 light years

Velocity of Sun around the Galaxy 220 km/s

Orbital period of Sun around the Galaxy 225 million years

Source: A Map of the Milky Way | AtlasOfTheUniverse

Links:
Where is Earth in the Milky Way? | UniverseToday
The Universe within 50000 Light Years - The Milky Way Galaxy | AtlasOfTheUniverse
Orion Arm | SciencePenguin.com
How to Find Your Way Around the Milky Way This Summer| | UniverseToday

last updated 17 Jan 2015