spectrum
If you look at a star through a prism, you will see a spectrum . The spectrum is the range of colors seen in a rainbow. The spectrum has specific dark bands where elements in the star have absorbed light of certain energies. An astronomer can use these lines to determine which elements are in a distant star. In fact, the element helium was first discovered in our Sun, not on Earth. This was done by analyzing the absorption lines in the spectrum of the sun.