What characteristic defines the type of stars necessary to power an emission nebula?

Answer

Extremely hot, massive stars, often spectral types O or B

These stars must have surface temperatures reaching tens of thousands of degrees to produce the intense ultraviolet radiation required for ionization on a grand scale.

What characteristic defines the type of stars necessary to power an emission nebula?

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How Does Ionization Cause Emission Nebulae To Glow? - YouTube

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