How Did Astronomers Determine That Elliptical Galaxies Are Composed Mostly

question 61

Multiple Choice

How did astronomers determine that elliptical galaxies are composed mostly of dark matter?

• A) They measured X-ray emission from hot gas gravitationally bound to the galaxies.
• B) They measured the rotation rates of gas as a function of distance from the centers of the galaxies.
• C) They measured the amount of gravitational pull elliptical galaxies have on companion galaxies.
• D) They assumed that the proportion of dark matter was roughly the same as in spiral galaxies.

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