Question

A star rotating at a slow speed gives a ____ spectral line because light is red-shifted and blue-shifted only _____ ____ from the center.

a) Narrow, closer
b) Broad, closer
c) Narrow, farther
d) Broad, farther

Answer 1

A slowly rotating star produces a narrow spectral line due to smaller Doppler shifts from the light being red-shifted and blue-shifted closer to the star's center.

Step-by-step explanation:

A star rotating at a slow speed gives a narrow spectral line because light is red-shifted and blue-shifted only closer to the center. Each point on the star has its own Doppler shift, leading to a sum of spectral lines originating from different velocities with respect to us.

When a star rotates slowly, the range of Doppler shifts is smaller, making the absorption line appear narrower. Conversely, rapid rotation causes a greater spread of Doppler shifts, which results in broad spectral lines, known as line broadening. This broadening can indicate the speed of the star's rotation.