
thumb|right|Cat's Eye Nebula (NGC 6543) thumb|Cat's Eye Nebula (NGC 6543) Nebulium was a proposed element found in astronomical observation of a nebula by William Huggins in 1864. The strong green emission lines of the Cat's Eye Nebula, discovered using spectroscopy, led to the postulation that an as yet unknown element was responsible for this emission. In 1927, Ira Sprague Bowen showed that the lines are emitted by doubly ionized oxygen (new style O; old style O), and no new element was necessary to explain them.
thumb|right|Cat's Eye Nebula (NGC 6543) thumb|Cat's Eye Nebula (NGC 6543) Nebulium was a proposed element found in astronomical observation of a nebula by William Huggins in 1864. The strong green emission lines of the Cat's Eye Nebula, discovered using spectroscopy, led to the postulation that an as yet unknown element was responsible for this emission. In 1927, Ira Sprague Bowen showed that the lines are emitted by doubly ionized oxygen (new style O; old style O), and no new element was necessary to explain them.
==History==
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).