Spiral Galaxies (4) ...
The most prominent feature of spiral galaxies is of course their spiral arms.
The Spiral Structure
The spiral structure
is associated with active star-forming regions. As already noted in
conjunction with the Milky Way, this is in
fact why the spiral arms of these galaxies are so prominent. Because they are
regions of active star formation, there are many hot young blue and blue-white
stars there, making the arms extremely visible.
The adjacent image shows a star-forming region called
NGC 206 that is located in the spiral arms of the nearby galaxy M31 (Andromeda).
Notice the diffuse
blue glow associated with many young stars in this active star-forming region.
