In 1864, the English astronomer Sir William Huggins made an amazing discovery. While looking at the Cat’s Eye Nebula through a spectroscope — a device that separates light into its component wavelengths – he observed green lines at wavelengths never seen before. This indicated a new chemical element, which Huggins named Nebulium.
It was an exciting discovery except for one tiny thing – Nebulium didn’t fit anywhere into the periodic table of the elements. But the periodic table had just been created (and was, in fact, erroneous in several respects), and the discovery of chemical elements was still in its infancy.