ASTR 402
Between the Stars: The Interstellar Medium Spring 2025
Division III Quantitative/Formal Reasoning

Class Details

The matter between the stars–the interstellar medium–tells the story of the evolution of galaxies and the stars within them. Stars are accompanied by diffuse matter all through their lifetimes, from their birthplaces in dense molecular clouds, to the stellar winds they eject as they evolve, and to their final fates as they shed their outer layers, whether as planetary nebulae or dazzling supernovae. As these processes go on, they enrich the interstellar medium with the products of the stars’ nuclear fusion. Interpreting the emission from this interstellar gas is one of astronomers’ most powerful tools to measure the physical conditions, motions, and composition of our own galaxy and others. In this course we will study the interstellar medium in its various forms, from cold, dense, star-forming molecular clouds to X-ray-emitting bubbles formed by supernovae. We will learn about the physical mechanisms that produce the radiation we observe, including radiative ionization and recombination, collisional excitation of “forbidden” lines, collisional ionization, and synchrotron radiation. Applying our understanding of these processes, we will analyze the physical conditions and chemical compositions of a variety of nebulae. Finally, we will discuss the evolution of interstellar material in galaxies across cosmic time. This course is observing-intensive. Throughout the semester, students will work in small groups to design, carry out, analyze, and critique their own observations of the interstellar medium taken using the rooftop telescope.
The Class: Format: tutorial; Tutorial meetings will be scheduled with the professor. Students will also complete observing projects using the rooftop telescope.
Limit: 10
Expected: 6
Class#: 3611
Grading: no pass/fail option, no fifth course option
Requirements/Evaluation: weekly problem sets, 10-page final paper, and observing projects
Prerequisites: ASTR 111 and PHYS 201 or permission of instructor
Enrollment Preferences: juniors and seniors
Distributions: Division III Quantitative/Formal Reasoning
QFR Notes: In this course, students will derive quantitative physical formulas, use these equations to calculate and compare physical properties, and generate and analyze graphical representations of data. They will also make and analyze measurements of astronomical data through observing projects.

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