Embedded Files
In the near future, we expect to be able to look at absorption spectra from light reflected off of nearby planets orbiting stars other than the Sun. These planets are called exoplanets. By looking at their absorption spectra, we hope to determine which exoplanets have water, oxygen and nitrogen on them, and therefore which planets are suitable for human habitation.
To see the absorption spectrum for our Sun, click here. To see an animation on the production and viewing of an absorption spectrum, click here.
When we view light from distant stars, galaxies, or galaxy clusters, we typically see absorption spectra. The absorption spectra tell us the chemical compositions of the surface gases of what we are looking at.
If however the light source is a gas that is glowing because of an electrical discharge flowing through it (or similar process), the associated spectrum is called an emission spectrum. Emission spectra are composed of very specific frequencies of light. These frequencies are associated with electrons jumping from one fixed orbital in an atom of the gas to another fixed orbital. Emission spectra are unique to each element of matter, and can be considered to be "atomic fingerprints" of each element.
When a continuous spectrum passes through a relatively cool, electrically neutral gas, the reverse process happens. The frequencies created in an emission spectrum are now subtracted from the continuous spectrum. The result is something called an absorption spectrum.
If the light being dispersed is coming from a source wherein charged particles are moving about randomly (like an incadescent light bulb), the spectrum is said to be continuous (like the one depicted in the image to the left).
When visible and spatially aligned light is passed through a prism (or equivalently, an etched glass called a diffraction grating), it is broken up into it's component colors, in a process called dispersion. The range of colors shown, from highest to lowest frequencies (or vice-versa), is called the light source's spectrum. The plural of spectrum is spectra.
Page updated
Google Sites
Report abuse