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Unformatted text preview: These lecture notes were prepared for Rutgers Physics 341/342: Principles of Astrophysics by Prof. Chuck Keeton, and modified by Profs. Saurabh Jha and Eric Gawiser. All rights reserved. c 2011 Lectures 1-2: Introduction I. What is Astrophysics? Astrophysics is the application of physical principles to astronomical system, such as planets, stars, galaxies, and the universe as a whole. The physical principles we will use include: gravity electromagnetism gas physics atomic physics nuclear physics Here are some of the systems we can study, and my attempt to categorize them by the physics they involve: gravity: planetary motion, asteroids, moons, rings, binary stars, extrasolar planets, supermassive black holes, galaxy dynamics, dark matter, gravitational lensing, expand- ing universe, dark energy, extra dimensions electromagnetism: light, jets, pulsars gas physics: planetary atmospheres, gas clouds (nebulae), gas in galaxies, accretion, black holes in binaries, quasars and active galactic nuclei atomic physics: stellar atmospheres, Greenhouse effect, gas cooling nuclear physics: fusion, stellar interiors, stellar evolution, supernovae, white dwarfs, neutron stars, nucleosynthesis, early universe Understanding gravity opens the door to studying many fascinating systems. This is our focus in Physics 341. We will take up the other topics in Physics 342. 1 II. Course Goals In my view one way to state the scientific method is this: We use theory to make quantitative predictions that can be compared with observations. Sometimes the equations we need to solve are easy. But often they are not! How do we proceed? In many cases we can use physical insight and approximate calculations to under- stand the salient features of a system without sweating the details. This is the motivation behind two of my goals for the course: 1. Understand physical principles and their application to astronomical systems. 2. Become skilled at estimation techniques: dimensional analysis scaling relations Taylor series expansions My hope is that you will learn to think like an astrophysicist. Rather than memorizing facts about some particular system, you will learn to break the system into pieces you can analyze, and understand it for yourself. I will show you how I do it. If the course is successful, you will be able to do it yourself to analyze and understand interesting systems that you encounter in the future, even if they were not covered in class. Lets not forget about a third goal: 3. Learn about exciting developments in astrophysics! Astrophysics is a very dynamic field of research and one in which you can understand the physical principles that underlie even the newest discoveries. So lets have fun!...
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- Fall '11