Sample Spectra of Gases
In the lab, we can produce the emission spectra from samples of different elements. We take bulbs filled with samples of different gases (hydrogen, neon, mercury, oxygen, etc.) and pass their light through a diffraction grating and see the following:
When we observe the spectra of astronomical objects, we see either emission lines or absorption lines at exactly the same wavelengths (or colors) as they are seen in these images of the spectra of Hydrogen, Neon, and Oxygen observed in the lab on Earth. When we match an emission line in a cloud of gas in space to the emission line from a Hydrogen bulb, we know that cloud must contain Hydrogen. In this way, we can determine the chemical composition of the most distant objects in space simply by observing their light.
The images on this page accompany the article "Simultaneous Display of Spectral Images and Graphs Using a Web Camera and Fiber-Optic Spectrophotometer" Niece, Brian K. J. Chem. Educ., 2006, 83, 761-764 and are provided with the permission of the Journal.