An emission nebula is a type of interstellar cloud of gas and dust that emits light due to the ionization of its hydrogen atoms. This ionization typically occurs when high-energy ultraviolet radiation from nearby hot stars excites the gas, causing it to emit light at various wavelengths, primarily in the red part of the spectrum from hydrogen-alpha emissions. Emission nebulae are often found in regions of active star formation and can be sites where new stars are being born.
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