How Do We Determine the Amount of Dark Matter in Elliptical

question 39

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 in the outer portion of the galaxy.
• B) We measure the broadening of the galaxy's absorption lines to infer the speeds of stars at different distances from the galactic center.
• C) We count the number of stars in the galaxy. Combining this with the galaxy's volume, 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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