What Is the Primary Way in Which We Determine the Mass

question 97

Multiple Choice

What is the primary way in which we determine the mass distribution of a spiral galaxy?

• A) We construct its rotation curve by measuring Doppler shifts from gas clouds at different distances from the galaxy's center.
• B) We calculate its mass-to-light ratio.
• C) We apply Newton's version of Kepler's third law to the orbits of globular clusters in the galaxy's halo.
• D) We count the number of stars we can see at different distances from the galaxy's center.

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