Light from Stars
The graphs below are idealized versions of the graphs you thought
about in Question 1. They show how the amount of light emitted by a star should vary
with the light's wavelength. The curves show the amount of light emitted as a
function of wavelength for two stars: one with a peak wavelength of 4000 Angstroms (top)
and one with a peak wavelength of 6400 Angstroms (bottom).
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Stars whose light has peak wavelengths of
4000 Angstroms (top) and 6400 Angstroms (bottom) |
Question 2. What colors would these two stars appear to your eyes?
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So analyzing the wavelengths of light that stars give off offers an answer to the question from the last section:
stars appear different colors because they emit light with different proportions at
different wavelengths.
Question 3. Some stars have peak wavelengths in the
infrared part of the spectrum, longer than red light. Can you still see these stars? Why
or why not? What color do they appear? What about stars whose peak wavelengths are in
the ultraviolet?
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Explore 3. What about stars whose peak wavelength
is green light? What color do they appear?
To find out, look through the SDSS database to find a few stars that emit
most of their light in the green wavelength (that is, stars whose g magnitude is
less than its other magnitudes. Look on your own, but if you can't find any,
here is a
hint. What color do these stars look to you? Was this what you expected?
Launch the Navigation Tool |
Question 4. Why do stars whose peak wavelengths lie in the green range
look the way they do?
HINT: Look at the visible spectra in the curves above and think about your
answer to Question 3. |
The Big Question
Now you see that stars look to be different colors because they have different
peak wavelengths of radiation. But you might be wondering why stars have different
peak wavelengths in the first place. Similarly, since all you can ever know about a star is the
light that arrives on Earth, can you use a star's peak wavelength to learn something
important about the star? Yes, you can. Click Next to find out how.
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