The Cygnus Arm or Outer Arm (labeled "+II") is one of four major spiral arms in the Milky Way galaxy, along with the Sagittarius Arm. The Outer Arm has a radius of 15.5 ± 2.8 kpc and lies outside the Perseus Arm. It is named after its proximity to the Cygnus constellation.

External link

• Galactic Structure, Galactic Rotation Curve and Measurements on the M31 galaxy