Reflection nebula

From South Dublin Astronomical Society

Reflection nebulae are clouds of gas and dust which simply reflect light from nearby stars without any significant activity within the cloud. As the light travels through the nebula, it gets scattered by the tiny particles of dust. This results in the nebula taking on a slight blue colour, similar to the way the daytime sky also appears blue. Reflection nebulae and emission nebulae are often seen in close proximity as they can often form from the same larger cloud of gas and dust. A good example of this is M20, The Trifid Nebula in Sagittarius which actually consists of both a pink emission nebula and a blue reflection nebula adjacent to each other.