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Quiz 7 – ASTR& 115 – TCC – Winter 2023
1.
In the 1920’s astronomers imagined the tuning fork diagram (shown below) as representing an evolutionary sequence for galaxies, with galaxies starting off as elliptical and developing more structure over time to become spirals and eventually losing structure to become irregulars (not shown in the diagram but would be to the right). They did not know much about galaxy colors and what they tell us about interstellar gas content, but you do. Carefully
explain how they got this one completely wrong.
2.
When astronomers point X-ray telescopes at clusters of galaxies, they detect X-ray emission from everywhere inside the cluster, not just the galaxies themselves. Explain how these observations imply that there is even more dark matter in the cluster than in all galaxies combined.
