When We See That a Spectral Line of a Galaxy

question 19

Multiple Choice

When we see that a spectral line of a galaxy is broadened,that is,spanning a range of wavelengths,we conclude that

• A)we do not have very good resolution of a star's orbital velocity.
• B)there are many stars traveling at extremely high orbital velocities.
• C)there are different Doppler shifts among the individual stars in the galaxy.
• D)we are actually measuring the orbital velocity of a cloud of atomic gas.
• E)we are actually measuring the orbital velocity of dark matter.

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