Fall 2017 Astronomy 241 M,W,F 10:30 — 11:20

ASTR 241 is a rigorous, calculus-based introduction to Solar System astrophysics. In this course, basic concepts of classical mechanics, thermodynamics, and modern physics are used to understand the structure and evolution of the Solar System. Our Solar System was the original proving ground for much of Newtonian dynamics, and it provides many opportunities to use physics on a grand scale. In addition to introducing the study of the Solar System, ASTR 241 presents wide-ranging applications of basic physics and an preview of numerical techniques. ASTR 241 is the first course in the astrophysics major.

Time & Place: Monday, Wednesday, Friday, 10:30 — 11:20 in Watanabe 114

Professor: Joshua E. Barnes (barnes at
Office: Institute for Astronomy, Room C-219 (956-8138)
Office hours: Mon 10:00 — 10:20 and 11:30 — 12:00, Fri 10:00 — 10:20 and 11:30 — 12:30
in Watanabe 401, or by appointment at the IfA

Text: Foundations of Astrophysics by Barbara Ryden & Bradley M. Peterson

Astronomy help: See any Astronomy TA in Watanabe 403; hours are posted outside.

Course Outline & Schedule

Dates Topic   Reading
8/21 8/23 8/25 Preliminaries Linear and circular motion. Dimensional analysis. Significant figures. Differential equations & numerical solutions.
8/28 8/30 9/01 Solar System Orientation Sun, planets, dwarf planets, asteroids, comets, dust, solar wind. Formation scenario. Other solar systems. Kepler's laws. 8.1, 2.3 — 2.5
  9/06 9/08 Deriving Kepler's Laws Mechanics & gravity. One-body problem and solution. 3.1
9/11 9/13 9/15 Orbital Motion Bound and unbound orbits. Conservation laws. Orbit calculation. 3.2 — 3.4
9/18 9/20 9/22 Hydrostatic Equilibrium Gas pressure. Isothermal atmospheres. Scale height. Convection. 9.2
9/25 9/27 9/29 Thermal Equilibrium Thermal radiation. Solar flux. Temperature equilibrium. Greenhouse effect. Escape of atmosphere. 8.2
10/02 10/04 10/06 REVIEW & MIDTERM
10/09 10/11 10/13 Terrestrial Planets Internal structure. Heat production & transport. Magnetic fields. Impacts, volcanism, erosion, plate tectonics. 9.1, 9.4, 9.5, 10.1
10/16 10/18 10/20 Giant Planets Gas giants & ice giants. Phases of Hydrogen. Gas sphere model. Internal structure. Heat flow. 10.2.1, 10.2.3
10/23 10/25 10/27 Earth, Moon, and Sun Earth-Moon system. Tidal forces. Response of oceans. Synchronous rotation. Precession of Moon's orbit. 4.1, 4.2, 4.4, 4.5
10/30 11/01 11/03 Satellites and Rings Satellites of giant planets. Roche & Hill radii. Resonances. Tidal heating. Nature of rings. Resonant structure of rings. 10.2.2, 4.3, 10.3
11/06 11/08   Small Bodies Asteroids and KBOs. Structure of belts. Orbital families. Comets. Sublimation physics. Tail dynamics. 11.1, 11.2, 11.3, 11.4
11/13 11/15 11/17 REVIEW & MIDTERM
11/20 11/22   The Sun. I Solar structure. Physical state of interior. Homogenious model; Kelvin-Helmholtz timescale. Particles & reactions. Hydrogen burning. 5.1, 5.2, 15.2, 15.3
11/27 11/29 12/01 The Sun. II Wave-particle duality. Tunneling. Energy transport mechanisms. Structure of the Sun. 15.1, 15.4
12/04 12/06   FINAL REVIEW

Discussions, Problem Sets, Exams, & Grades

Friday class sessions will usually be devoted to classroom discussion, with an emphasis on problem-solving. To motivate the discussion, a problem set will be distributed at the start of the week. These problem sets will be reviewed by students working in small groups and by the class as a whole. The objective is to make sure that everybody knows how to solve the assigned problems.

Written solutions to the problems will be due the following Wednesday (bold dates in syllabus) at the start of class. Late work must be handed in by Friday, and will receive 70% credit. Work will be graded and returned to the class on Monday.

There will be two midterm exams, on 10/06 and 11/17. Review classes will be given before each exam. The final exam will be given from 9:45 to 11:45 on 12/11 in Wat. 114. The final is cumulative.

In-class participation, problem sets, midterms, and the final are worth 15%, 30%, 25%, and 30%, respectively. You must take the final to receive a passing grade.

Learning Objectives

This course introduces the Solar System as an arena for physics, and teaches students to solve Solar System problems by applying basic physical laws. ASTR 241 students will be able to calculate orbital trajectories, evaluate surface temperatures for planets without and with greenhouse atmospheres, apply hydrostatic equilibrium to the atmospheres and interiors of planets and the Sun, estimate the physical consequences of interactions and collisions between Solar System objects, explain how the Sun mantains its luminosity over billions of years, and discuss mechanisms which transport energy throughout the solar system. Students will also be introduced to simple numerical techniques.

This course aligns with a number of UH Manoa's Institutional Learning Objectives, including: objective 1a (general understanding of the Universe), objectives 2a (critical and creative thinking, problem solving, mathematical reasoning) and 2c (collaborative work with peers), and objectives 3a (intellectual curiosity) and 3c (respect for resources).

Research experience is critical for anybody contemplating a career in astrophysics. We will schedule an afternoon/evening meeting for all Astrophysics and Astronomy majors to present a selection of possible research projects.

Joshua E. Barnes      (barnes at
Updated: 20 August 2017
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