What does the doppler effect tell us about stars' rotations?

On Sat, 21 Nov 1998, Mr. Stinky wrote:

Dear Greg,

Yes, the rotation of stars is measured with the Doppler effect. As one
side of the star rotates toward us, the light of atomic spectral lines is
blueshifted, and the light from the side of the star rotating away from
us is red-shifted. Since we cannot resolve the surface of the star, what
we wee in the spectrum is a broadened absorption line. By the width of
the line, we can tell how fast the star is spinning. The faster the
spin, the broader the line!

Thanks for writing.

Sincerely,
Kurtis Williams

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