... Our Galaxy in Stars, Gas, and Dust . ... Credit: John P. Gleason , Celestial Images Explanation: The disk of our Milky Way Galaxy is home to hot nebulae, cold dust, and billions of stars. The red nebulae visible in the above contrast-enhanced picture are primarily emission nebulae , glowing clouds of hydrogen gas heated by nearby, bright, young stars. The blue nebulae are primarily reflection nebulae, clouds of gas and fine dust reflecting the light of nearby bright stars. ... The Milky Road . ...