From "Astronomy! A Brief Edition," J. B. Kaler, Addison-Wesley, 1997.
Excited electrons, don’t stay excited forever.
Drop back down to their ground floors.
Only light of the precise energy difference between floors is given off.
This light goes off in all directions.
From a second detector, we see these specific energy wavelengths: an emission spectrum.
Continuum, Absorption, Emission
Heat low density gas and it will glow.
Pass the light through a slit to get a narrow source.
Pass light from the slit through a prism.
Get multiple images of the slit, each at a different wavelength.
These “lines” are the element’s “finger print”.
Every element has a DIFFERENT finger print.
Gases, stars, planets made up of MANY elements have spectra which include ALL of the component spectral lines.
It’s the scientist’s job to figure out which lines belong to which element.
Different stars have different types of spectra.
Different types of spectra mean different stars are made of different elements.
Annals of the Harvard College Observatory, vol. 23, 1901.
EVERY element has a SPECIAL set of lines.
Observe the lines and you identify the component elements.
Learn about the environment of the element
The sunlight we see is thermal radiation caused by the extreme heat of the sun’s surface. However, the very top thin layer of the sun’s surface is relatively cooler than the part below it. What type of spectrum would you expect to see from the sun?
A continuous spectrum.
A continuous spectrum plus a second, slightly redder continuous spectrum.
A continuous spectrum plus a second slightly bluer continuous spectrum.
A continuous spectrum plus an emission spectrum.
A continuous spectrum plus an absorption spectrum.