Spectral line
Soon, scientists discovered that when they heated other chemical elements, like calcium and oxygen, so hot that they shined with a white light, they found similar lines, but in different places. No two chemical elements had these lines in exactly the same places along the rainbow, and they also soon discovered that could be used to be able to tell what stars were made up of in the Universe. The lines that a particular element produces are called the emission spectrum of that element.