Fig12_4 Spiral arms of the Milky Way

Fig12_4 Spiral arms of the Milky Way

Fig. 12.4 . Luminous emission nebulae, known as ionized hydrogen, or H II, regions, act like beacons that mark out the inner spiral structure of our Milky Way. The Sun and solar system are located at the upper center, in a local spur from the nearest arm. The figure is centered at the center of our Milky Way. The scale, shown in the lower right, extends across 16,300 light-years.

Copyright 2010, Professor Kenneth R. Lang, Tufts University