What causes an emission nebula to frequently display a characteristic deep red hue?
Answer
Excited hydrogen atoms releasing energy
In an emission nebula, energetic ultraviolet radiation from young, hot stars ionizes the gas. When electrons recombine with atoms, energy is released as visible light, often resulting in a red glow due to the abundance of hydrogen.

#Videos
What Is A Nebula? - YouTube
Related Questions
What are the primary gases making up the fundamental composition of a nebula?What two major roles do nebulae play in the cycle of stellar evolution?What is the meaning of the Latin word *nebula*?How does the density of even the densest parts of a nebula compare to the best vacuum achievable in a laboratory on Earth?What specific entity forms at the center of a region undergoing gravitational collapse within a stellar nursery?What causes an emission nebula to frequently display a characteristic deep red hue?What physical principle causes reflection nebulae to typically appear blue?What mechanism leads to the formation of a planetary nebula?What is characteristic of the material comprising a supernova remnant?Approximately how wide is a relatively small emission nebula like the Orion Nebula?