BSL Physics Glossary - line emission spectrum - definition
When an electric current passes through a gas, it gives energy to the gas. This energy is then given out as light of several definite wavelengths (colours). This is called a line emission spectrum. Each element has its own particular spectrum by which it may be identified. This enables astronomers to identify elements present in the distant stars; eg, a spectrum which identified sodium would have 2 distinct yellow lines (unique to sodium).