Nebulium

Nebulium (rarely Nebulum or Nephelium ) is the name for a postulated in the 19th century hypothetical element. He was given the green emission lines in the spectrum of planetary nebulae and diffuse nebulae associated ( cf. emission nebula ).

Discovery

William Huggins discovered in 1864 in the planetary nebula NGC 6543 ( Cat's Eye Nebula, constellation Draco ) first light glowing lines with the wavelengths 3726, 3729, 4959 and 5007 Angstroms. As a possible explanation for their presence he proposed the existence of a not yet found on earth element, the Nebuliums before.

Explanation

Only in 1927 identified Ira Bowen alleged nebulium lines: These are so-called forbidden lines of the (double) ionized oxygen, nitrogen, helium, neon, and some other gases. These forbidden lines can (like an earthly high vacuum) occur only in the very low density of gaseous nebulae. In the laboratory, under normal terrestrial conditions, occur these lines because of the very low transition probability practically non-existent and therefore can not be detected. The lines are called for historical reasons, partly to date with N1 and N2, which have nothing to do with the element nitrogen. Forbidden lines are now given in square brackets, such as [O III ].