Physics 105 Spring 2012
Syllabus and Schedule

Readings: Ryden and Peterson Ch. 1. Material on timekeeping was not covered in lecture but please read it. This material is also covered at a somewhat more basic level in elementary astronomy texts, e.g. The Cosmic Perspective by Bennett, Donahue, Schneider and Voit.

After some preliminaries and logistics, we'll cover some of the basics of astronomy: the celestial sphere, different kinds of coordinate systems on a sphere, and celestial motions.

Readings: Ryden and Peterson Ch. 2.5, Ch. 3. We won't be covering most of the historical material in Ch. 2, but it's interesting and I encourage you to read it. We will not cover Ch. 3.4 on the virial theorem, but may come back to it later in the course.

After a very brief review of Newton's Laws and Newton's Law of Universal Gravitation, we'll start to look at their consequences for celestial motions-- in particular, we'll cover Kepler's Laws of planetary motions. I will derive the second law using Newton's Laws, and the fact that the gravitational force is a central force, and then I will derive the first law using the inverse square nature of the gravitational force.

Readings: Ryden and Peterson Ch. 3.2, 3.3, Ch. 5.1

I will first finish up some material on orbital energetics and some applications of orbital mechanics. We'll then start a new topic very important for astrophysics: the physics of interaction of light and matter, starting with the Bohr atom.

This lecture will be replaced by an observing session later in the semester. The next two lectures will also be replaced by Friday lectures at 8:30 am.

Readings: Ryden and Peterson Ch. 5.1-5.3. We didn't cover all of 5.3 but please read it (also the material on the Maxwell-Boltzmann distribution will be covered later).

We'll review the Bohr atom, and discuss atomic transitions, physical processes leading to these transitions, emission and absorption spectra, and broadening of spectral lines.

Readings: Ryden and Peterson Ch. 5.4, 5.6, 5.7. Some of this material is covered in somewhat more detail in the text than we will be doing in class, but please read it and go through the derivations.

I will define a number of terms useful for description of passage of light through macroscopic matter, and we will derive the equation of radiative transfer (in its simplest form). We'll then cover some basic thermodynamic concepts: the Maxwell-Boltzmann distribution, thermodynamic equilibrium, the Boltzmann and Saha equations for determining relative populations of atomic states. Finally, we'll discuss blackbody radiation.

Readings: Ryden and Peterson Ch. 5.7, 6.1, 6.5

We'll first finish up some material from the end of Chapter 5: definitions of intensity, specific flux, flux and luminosity, and applications to a blackbody. Then we will start to discuss some details about the observation of photons. I'll cover some very basic concepts related to the collection of images. We will then start discussing statistics of photon counting.

Readings: Ryden and Peterson Ch. 6.2-6.6. Some material will be covered in less detail in class, and a few things will be covered in a bit more detail than in the text.

I will finish up material from last class on photon counting, and signal-to-noise concepts. We will then talk about different kinds of telescopes, and related topics: reflectors and refractors, spectroscopes and detectors, "seeing" and adaptive optics. I will briefly discuss astronomy at wavelengths other than visible, and "multimessenger" astronomy (cosmic rays, neutrinos and gravitational waves): we'll come back to the latter later in the course.

Readings: Ryden and Peterson Ch. 7.1-7.2

We will discuss observational aspects of solar physics: the observable layers of the Sun, and phenomena associated with solar activity.

Readings: Ryden and Peterson Ch. 8. We didn't get to the material on atmospheres in section 8.2 in class, but please read it. There is much more in-depth material about the solar system in Chapters 9-11, but we will be skipping them (they may be of interest for those pursuing projects, however). There is also a summary of material about solar system formation in Ch. 12.1 and 12.2.

We will cover basic properties of the solar system. I'll discuss the classification of solar system objects, and we'll briefly and qualitatively go through what is known about formation of the solar system. Then we will look at physical properties of solar system objects with a bit more of a quantitative eye: we'll look at mass, density, and temperature of solar system bodies.

Readings: Ryden and Peterson Ch. 12.3-12.4. I will cover some material not in your textbook.

We will discuss techniques for detection of planets around stars beyond our own solar system, and the current rapidly-expanding state of knowledge.

Readings: Ryden and Peterson Ch. 13.1-13.3. Please also read 13.4 and 13.5, although we will not be covering this material in much detail in lecture. There is also some basic material on parallax at the end of Ch. 2 that you might want to go back to.

We will discuss properties of stars from an observational point of view. We'll discuss how to measure distances to relatively nearby stars using parallax. I'll define various terminology relating to stellar brightness, and discuss how to make measurements of stellar luminosity and temperature. Your text has material on how to determine stellar masses and radii.

Readings: Ryden and Peterson Ch. 9.2, pp. 213-216 on hydrostatic equilibrium, Ch. 14. We will refer back to 5.6 on spectral line strengths as a function of temperature.

We will first discuss hydrostatic equilibrium in stars, as background information for discussion of stellar atmospheres (and we will refer back to this material in future discussion of stellar evolution). Next, we will discuss the standard stellar classification scheme which labels stars by their spectra, and maps stars to their surface temperatures. We will also discuss luminosity class, which relates width of spectral lines to star size. Finally, I will introduce the celebrated Hertzsprung-Russell diagram, which plots luminosity versus temperatures, and enables classification of stars by physical nature.

• The midterm will be closed book.
• Calculators are allowed; however you may use them only for simple computations, not graphing, equation-solving etc.
• You may bring with you a "cheat sheet", on which you can write anything you like on one side of the paper. Include any formulae and physical constants you think you will need. You don't need to include things like data for astronomical objects, as such will be given to you if needed. You must hand in your cheat sheet with your test.
• Material covered in the test corresponds to the readings listed above, along with supplemental material from lecture. At least one question from the homework will be included on the test.

Readings: Ryden and Peterson Ch. 14. I will not cover all the derivations of the equations of stellar structure in detail in lecture, but please read the material. I will also cover some additional material on solar neutrinos not in the textbook.

We will discuss the equations of stellar structure: hydrostatic equilibrium, mass continuity, radiative transport (radiation and convection), equation of state, and energy generation. The basic idea is that one can model stellar structure (density, pressure and temperature as a function of radius) by solving these coupled differential equations. Then, I'll discuss the specifics of energy generation via fusion reactions. Finally, we'll see how it's possible to test these models, using helioseismology and neutrinos.

Readings: Ryden and Peterson Ch. 17.1-17.2, very beginning of Ch. 18. I will also cover some material not in the textbook.

We will discuss the lives of stars from birth to death. We will cover conditions for stellar formation, and the dependence of stellar destiny on mass. We'll look at the evolution of a Sun-like star. We'll also look at what happens to stars much more massive than the Sun, through to their spectacular demises as core-collapse supernovae.

Readings: Ryden and Peterson, Ch. 18.1, 18.2, 18.4. There is some material back in 13.5 about measurement of mass and radius properties of the Sirius system that is relevant to this lecture.

This lecture will cover the nature of the exotic corpses of low and high mass stars. I will discuss properties of white dwarf stars and the degenerate-electron matter they are composed of. We'll briefly cover novae and white dwarf supernovae, before discussing what happens when the mass of a star is too large to be supported by degenerate electron matter: in this case a neutron star forms. When the mass is too high to be supported by degenerate neutron matter, a black hole will form.

Readings: Ryden and Peterson Ch. 18.3, 19.1, 19.2, 19.7. I will cover briefly other selected topics from Ch. 19, as well as some material not in your textbook.

I will discuss basic properties of black holes: mass, Schwarzschild radius, event horizon. We'll discuss what happens if you go near a black hole. Then we'll switch to a different topic: our Milky Way galaxy. I'll cover morphology and some dynamical and evolutionary features, and we'll touch upon galactic velocity curves, which gave the first evidence of the existence of dark matter (we'll come back to that topic later in some detail). Finally, I'll connect back to the topic of black holes, and discuss what's known about the supermassive black hole at the center of the Milky Way. We'll revisit black holes later in the course after covering some material on general relativity.

Readings: Ryden and Peterson Ch. 20.1, 20.4, 20.5; we will touch on a few things in 20.2. We will also go back to some material on Cepheid variables from 17.3, and I will touch on material on galaxy collisions in 22.2 (we may come back to it next lecture, if there's time). I will mention active galaxies briefly-- these are discussed in Ch. 21-- but we will be skipping most of the detailed material on that topic. We will also cover a few topics not in your text.

I will discuss classification of galaxies into ellipticals, spirals and irregulars, and some of the subcategories of these. I'll briefly mention theories for formation of galaxies (which is not much discussed in your text), and galactic collisions. Then we'll move to a different, but related, topic: the "cosmic distance ladder" of techniques allowing determination of distances to cosmic objects. The nearest rungs we've discussed already: these are radar ranging and parallax. To determine distances beyond about 200 pc, "standard candles" are required. The Main Sequence serves as a kind of standard candle, for star clusters within the Galaxy. Cepheid variable stars, which have a known period-luminosity relation, and white dwarf supernovae, work as standard candles for distant galaxies. Beyond that, the Hubble relation can be used: I'll introduce Hubble's discovery of the expanding universe.

Readings: Ryden and Peterson Ch. 22. We will also use some material from Ch. 20, pp. 478-479, but apply it to galaxies rather than stars. The derivation of the virial theorem is in Ch. 3.4 (but we will not go through it).

We will discuss groups and clusters of galaxies, and look at some properties of "nearby" ones. We'll use the virial theorem to estimate the mass of the Coma cluster. Next, we'll look at collisions between large objects in a bit more quantitative detail than last lecture: we'll look at rate of collisions for stars and galaxies, and consider the consequences. Stellar collisions are rare, but galactic collisions are common. Finally, we'll look at the largest known structures in the Universe: superclusters, and voids, which can be mapped based on redshift measurements.

Readings: We will not be following the text for this lecture. This material can be found in many intermediate-level modern physics texts, e.g. Modern Physics by Serway, Moser and Moyer.

I will cover the basic concepts of special relativity. First I'll discuss the Michelson-Morley experiment and its failure to discover the "ether". I'll then introduce Einstein's postulates and the concept of simultaneity. The postulate that the speed of light is constant has some nonintuitive consequences: time dilation, length contraction. We'll also cover Lorentz transformations, which can be used to derive the formulat for relativistic addition of velocities. I will introduce some concepts of the general theory of relativity, which describes accelerating reference frames (to be continued next class).

Readings: Ryden and Peterson Ch. 23.3. I will also cover material not in the textbook.

We will discuss the basic concepts behind Einstein's general theory of relativity: the principle of equivalence (of gravity and acceleration) and the idea of curved spacetime. Then we will discuss the experimental observables of general relativity: the precession of Mercury, curvature of light, gravitational lensing, gravitational redshift, and gravitational waves. If there's time, we'll revisit black holes and touch on some more speculative topics.

Readings: A fair amount of today's material is not in the text, although some is to be found in Ch. 19.2 and 22.1.

We will first review the considerable evidence for dark (non-electromagnetically-interacting) matter. We've already touched upon some of this in various lectures, but I will summarize it: there is evidence for extra mass in Universe from galaxy rotation curves, and galaxy velocities and hot gas temperatures in galaxy clusters. Weak gravitational lensing surveys allow mapping of matter in galaxy clusters. Next, I'll go over methods for understanding the nature of the dark matter, which is a very active worldwide ongoing scientific endeavor on many fronts. I'll discuss MACHOS, WIMPs, and direct and indirect methods of WIMP detection.

Readings: Ryden and Peterson Ch. 23.1, 23.2

I'll discuss the main evidence we have for the universe's expansion and cooling from an initially hot and dense state: the darkness of the night sky, the Hubble observation of redshift vs distance, and the cosmic microwave background radiation. We'll discuss the (limited) description of the expansion of the universe in a simplified Newtonian framework.

Readings: Ryden and Peterson Ch. 23.3, 23.4

We'll review some concepts of curved spacetime, and discuss observational evidence for the flatness of the Universe. I'll discuss various "metrics" used for determining distances for different geometries, and introduce the Robertson-Walker metric. We will consider how to determine distances in expanding spacetime, and connect them to observed redshifts. We'll then discuss the Friedmann equation connecting expansion of the Universe to its curvature and energy density.

Readings: Ryden and Peterson Ch 24.1, 24.2

I will discuss the behavior of solutions to the Friedmann equation (describing expansion of the Universe) for different relative amounts of radiation, matter, and "lambda" energy density. We'll then discuss what observations tell us about this evolution: in particular, observations of distant supernovae tell us that the Universe's expansion is accelerating, which indicates that a "lambda" contribution must be present. This component of the energy density of the Universe is sometimes called "dark energy", and its origin and nature are basically unknown. We'll then discuss the "Concordance Model" of cosmology, for which a number of independent observations point to a particular mix of energy densities.

Readings: Ryden and Peterson, Ch. 24.3, 24.4. I will cover some material not in the textbook.

We will go backwards in time and talk about what's known about the very early universe. First we'll discuss Big Bang Nucleosynthesis. Next, we'll talk about the earlier "particle" and "electroweak eras", and how we can try to learn about these eras via experiments on Earth. Finally, we'll discuss two problems with the overall picture. The "flatness problem" is the puzzling observed flatness of the Universe, when one would expect small deviations to have been amplified by expansion. The "horizon problem" is the puzzling homogeneity and isotropy of the Universe, when one would expect distant regions to have never been in contact. The theory of inflation-- which postulates exponential expansion at very early times-- solves both of these problems.

Project deliverable due
Homework 12 due

• The exam will be closed book.
• Calculators are allowed; however you may use them only for simple computations, not graphing, equation-solving etc.
• You may bring with you a "cheat sheet", on which you can write anything you like on both sides of the paper. Include any formulae and physical constants you think you will need. You don't need to include things like data for astronomical objects, as such will be given to you if needed, and you will be given the constants from the inside covers of the text. You must hand in your cheat sheet with your test.
• Material covered in the test corresponds to the readings listed above, along with supplemental material from lecture. At least two questions from the homework will be included on the test. All course material will be covered, although there will be slight weighting towards the end of semester.