Spiral Arms of the Milky Way

Our solar system is located in a spiral arm called the Orion Arm or Local Arm. Our arm is a small, intermediate arm connected to a more substantial next inner arm and next outer arm. The next inner arm is called the Sagittarius or Sagittarius-Carina Arm, the next outer arm is the Perseus Arm. One more outer arm and two more inner arms have been identified.

A list of the Milky Way spiral arms follows, sorted from outside to inside near our solar neighborhood in the Galaxy:

•  +II Outer Arm, Cygnus Arm
•   +I Perseus Arm
•    0 Local Arm, Orion Arm
•   -I Sagittarius Arm, Sagittarius-Carina Arm
•  -II Scutum-Crux Arm
• III Norma Arm

Just for fun, this map shows the four galactic quadrants from the Star Trek universe, which are an entirely fictional creation. Astronomers do not divide the Galaxy into quadrants.

Into the Halo

The following images illustrate the disk, bulge, and halo of the Milky Way. Globular star clusters orbit around the galactic bulge in elliptical orbits which often take them far out into the halo of the Galaxy.

Side View of the Milky Way

Different Milky Way Orbits

Images:
The galactic maps shown here are from the Canadian Galactic Plane Survey site located here.
The second image depicting galactic orbits is copyright of Addison Wesley publishing.
Images are shown here for noncommercial educational purposes.