Entry from US English dictionary
nounChemistry , historical
A hypothetical chemical element proposed in the 1860s to explain certain lines in the spectra of nebulae, later discovered to arise from forbidden transitions in oxygen and nitrogen ions.
- The hypothetical nebulium was simply the signature of ordinary oxygen doing extraordinary things.
- Coronium and nebulium were both, in the event, figments of the astronomers' imaginations.
- They called this unknown ‘new’ element nebulium, but modern astronomy has since shown it to be a rare form of superheated oxygen.
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