If a disk galaxy is reasonably close and edge-on,the Doppler shift of the galaxy disk material relative to the centre can be measured at several distances from the galaxy's centre.What does this measurement tell us about the galaxy?
A)the galaxy's luminosity
B)the galaxy's diameter
C)the galaxy's mass
D)the galaxy's velocity dispersion curve

Question

Quizplus · Accepted Answer

The Doppler shift measurement of the galaxy disk material tells us about the galaxy's mass since this measurement relates to the rotational speed of the galaxy. The faster the rotational speed, the more massive the galaxy. This is known as the Tully-Fisher relation. The other choices are not directly related to the Doppler shift measurements.

If a Disk Galaxy Is Reasonably Close and Edge-On,the Doppler