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More Temperature and Line Strength
Different elements absorb light, and thereby produce absorption lines, at different temperatures. You found in previous exercises that a star needs just the right temperature for the hydrogen alpha transition to occur.
Because absorption lines require that electrons start at a certain energy level, different absorption lines are prominent at different temperatures. The graph below shows the relative line strength for a given element versus temperature.
Look back at your answer to Question 12 - the spectral class with the strongest hydrogen absorption. Does that answer make sense when you compare it with what you see in the graph?
Another Way to Classify
We have used two different methods to classify stars - the hydrogen lines (Hα, Hβ, Hγ, Hδ) and the continuum peak wavelength. But professional astronomers usually use a slightly different method. They look for the presence (or absence) of several spectral lines to classify stars.
The table below lists some of the spectral lines that they look for, and the lines' approximate locations in the electromagnetic spectrum.
Once they have found the spectral lines they need, they classify the stars based on what spectral lines are present. Here are the lines they look for to identify what spectral class a star belongs to:
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