How Do We Determine the Amount of Dark Matter in Elliptical

question 7

Multiple Choice

How do we determine the amount of dark matter in elliptical galaxies?

• A)We measure the orbital velocities of star-forming gas clouds around the outer portions of the galaxy.
• B)We measure the speeds of stars at different radii from the galactic center and determine how much mass is interior to the orbit.
• C)We count the number of stars in the galaxy and determine its volume,so that we can calculate the galaxy's density.
• D)We search for dark lanes of dust and black holes within the galaxy.
• E)We measure how fast the galaxy rotates as a whole.

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