Quiz 7 (1)
docx
keyboard_arrow_up
School
Tacoma Community College *
*We aren’t endorsed by this school
Course
101
Subject
Astronomy
Date
Apr 3, 2024
Type
docx
Pages
4
Uploaded by MinisterBravery13752
Name:
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.
In this diagram, astronomers forgot to account for the fact that galaxies do not all have the same age, and that the interstellar gas content is different from galaxy to galaxy. For instance, an elliptical galaxy
looks very red and lack interstellar gas, while a spiral galaxy looks blue due to many bright young stars and abundant gas. Therefore, the diagram does not make sense as the galaxies are aging backwards. 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.
The hot X-ray emissions mean that there is gas inside the clusters. This hot gas means that the galaxies in the clusters are moving very fast, and there must be dark matter in these clusters helping to retain the
gas, as the mass of just what is inside the galaxies would not be enough to contain the gas without dark matter. 3.
The graph below proves that the expansion rate of our Universe is accelerating as the Universe gets older, an effect attributed to dark energy. Explain the reasoning following the requirements below.
In your response, make sure to answer the following questions:
What does each data point represent and where are we located on this diagram?
Which region of the graph corresponds to our Universe a long time ago and which region represents the more recent Universe?
How do you know that the expansion rate is not constant? Hint: why is there a straight solid line on the graph? Note that it does not represent all the data very well, only the nearest galaxies.
How do you know that the expansion rate of our Universe is increasing with time?
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Each data point represents a different galaxy in our universe. We (the Milky Way) are located at (0,0) on the graph. The upper right region corresponds to our Universe a long time ago, and the bottom left corresponds to our more recent universe. We know that the expansion rate is not constant, as we can see the galaxies don’t follow the blue trend line. We also know that the expansion rate is accelerating because the trend line is becoming more steep over time. (Galaxies moving faster at a closer distance from the Milky Way)