Science 10 with CSS teacher

The sun gives off light because the elements in it are heated to very high temperatures. Recall that an element is a substance that is made up of only one kind of atom. Every element produces a distinct colour when it is heated.

For example, when hydrogen is heated, only a few thin bands of light are produced. This same spectrum is produced whenever hydrogen is heated. On the other hand, no other element produces the same spectrum. You can think of an element's spectrum as its fingerprint. No two people have the same fingerprint, and no two elements have the same spectrum. This means we can identify an element by the spectrum it produces.

So what does this have to do with the stars? Well, astronomers can use spectroscopes to analyze the light given off by a star. They can determine what elements make up the star based on the spectra that the light produces. Stars are made up of relatively few elements: hydrogen, some helium, and traces of heavier elements such as iron. Over time, stars use up their hydrogen.