Module 10 Questions – Spiral Arms

Module 10 Questions – Spiral Arms

This discussion covers question 12, “ One reason trailing spiral arms form (and then may dissipate) in the disk of our galaxy is because stars farther from the galactic center than the sun take a ____________ than the sun to go around the galactic nucleus, while stars closer to the center take ____________. My choice was “a longer time, a shorter time.”

Spiral arms result from complex gravitational interactions among stars, star clusters, gas, and dust. They are temporary structures that can form, evolve, and dissipate depending on various factors. Trailing spiral arms trail behind the rotation of the galaxy. They are regions of increased star formation and are often populated by young, hot, massive stars, which give them a blue color. The Milky Way exhibits differential rotation whereby stars in different parts of the galaxy orbit the galactic center at different speeds. Stars farther from the galactic center  take longer to complete one orbit, while stars closer to the center take a shorter time to orbit. Stars farther out have longer orbital periods, hence taking longer time, while stars closer in have shorter orbital periods and, therefore, a shorter time. Stars have different velocities because they differ in distance from the center of the galaxy and different orbital periods. Stars with shorter orbital periods cover a shorter distance, hence a higher velocity, compared to stars further away, which cover a longer distance, resulting in a slower velocity. Therefore, stars closer move more quickly than stars further away from the center of the galaxy. Distance from the center of the galaxy, relative motion, and orbital period determine the time stars take to go around the galactic center.

The module is equipped with tools to navigate the stars and understand the celestial bodies. The module questions are useful to test and review the knowledge of the Milky Way.

References

Seeds, M. A. & Backman, D. (2018). ASTRO 3: Introductory astronomy. Cengage Learning.

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Instructions

• Each set of questions is titled with information, including the associated material.
• The questions approximately follow the order of the topics in the lecture.
• Open and use any interactive animation links preceding some questions.
• Answer the specified questions associated with each lecture. Save the document and use it to study for the Module Quiz.

One reason trailing spiral arms form (and then may dissipate) in the disk of our galaxy is because stars farther from the galactic center than the sun take a ____________ than the sun to go around the galactic nucleus, while stars closer to the center take ____________. C

1. 1. a longer time, a longer time.
   2. a shorter time, a longer time.
   3. a longer time, a shorter time.
   4. a shorter time, a shorter time.