nebulium

[nuh-byoo-lee-uhm]
noun Astronomy.
a hypothetical element once thought to be present in emission nebulae because of certain unidentified spectral lines, now known to be forbidden transitions of oxygen and nitrogen ions.

Origin:
1895–1900; nebul(a) + -ium

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To nebulium
Encyclopedia Britannica
Encyclopedia

nebulium

hypothetical chemical element whose existence was suggested in 1868 by the English astronomer Sir William Huggins as one possible explanation for the presence of unidentified (forbidden) lines (at 3,726, 3,729, 4,959, and 5,007 angstroms wavelength) in the spectra of gaseous nebulae. In 1927 the American physicist and astronomer Ira S. Bowen correctly determined that the common elements oxygen and nitrogen ionized (i.e., electrically charged) under conditions unobtainable on Earth are responsible for these spectral lines. See also forbidden lines.

Learn more about nebulium with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source
Example sentences
These lines defied explanation for over fifty years, lending speculation they were due to a new element, which was named nebulium.
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature