At first it was hypothesized that the line might be due to an unknown element, which was named nebulium—a similar idea had led to the discovery of helium through analysis of the Sun's spectrum in 1868.
起初，這條譜線被假設為一種未知元素的譜線，並命名為（Nebulium）－相同的想法在1868年分析太陽的光譜時，導致氦元素的發現。