What phenomenon explains spectral lines observed in nebulae that cannot be reproduced in dense terrestrial labs?
Answer
Forbidden lines resulting from extremely low density
These spectral lines, such as the green glow from doubly ionized oxygen, are known as forbidden lines because the near-vacuum (low density) of the nebula allows atoms to remain in specific long-lived excited states long enough to emit the photon, something impossible in dense Earth labs.
#Videos
How Does Ionization Cause Emission Nebulae To Glow? - YouTube
What Makes An Emission Nebula (HII Region) Glow? - YouTube
Related Questions
What percentage of atoms in an emission nebula is typically hydrogen?Why are emission nebulae frequently referred to as HII regions by astronomers?What stellar spectral types are usually responsible for powering an emission nebula?What specific energy band must photons possess to initiate the ionization of gas in a nebula?What atomic process causes the nebula to actually produce visible light after ionization has occurred?What is the primary cause of the rich, reddish hue observed in most emission nebulae?In contrast, why do reflection nebulae typically appear blue?What is the approximate kinetic temperature of the gas within a typical glowing emission nebula?What phenomenon explains spectral lines observed in nebulae that cannot be reproduced in dense terrestrial labs?Why is the brilliant glowing phase of an emission nebula considered cosmically ephemeral?