What condition characterizes hydrogen in H II Regions, and what is required to sustain this state?

Answer

Ionized ($ ext{H}^+$), requiring intense ultraviolet radiation from nearby hot, young stars.

Ionization of hydrogen necessitates highly energetic photons which strip electrons from the atoms, leading to the characteristic emission nebulae.

What condition characterizes hydrogen in H II Regions, and what is required to sustain this state?
SpaceastronomycompositionnebulaElements