Astro 110: Review for the midterm

The exam will consist of a mixture of short-answer questions and numerical problems (similar in type to the questions and problems that have been assigned at the ends of chapters, and on the quizzes). The exam will begin at 2:30 and end promptly at 3:45. You may not consult notes or textbooks during the exam, or give or receive aid in any way. As always, the Connecticut College Honor Code applies to all aspects of the exam.

You will not be expected to memorize formulas or most numerical constants -- they will be given to you, unless I have explicitly told you to memorize them. However, you will be expected to know what the equations mean, which quantities they relate, and when they are to be used. You must also know how to transform an equation that applies to one star into an equivalent equation that can be used to compare the properties of two different stars.

You must bring a calculator to the exam! You will not be allowed to borrow one! Don't forget!!

The following are a list of topics and questions that we have studied over the last six weeks. It is not an exhaustive list, nor will all of these topics necessarily appear on the midterm. It is simply meant as a way to help guide your studying. You should also review the end-of-chapter problems, the quizzes, and your notes.

Chapter 1

Understand angular measures, and how angular size is related to linear size and distance (via the small-angle formula). Be proficient with powers-of-ten (scientific) notation. Know how to convert between different units if you are given the conversion factors. How many nanometers (or centimeters, or blah-blah-meters) are there in a meter? (You must know this for the exam -- this kind of information will not be given to you.) What is the definition of an AU, a light-year, a parsec? How is distance related to speed and time?

Chapter 2

What is a constellation? Describe how the stars appear to move during the course of a night, and why they seem to do so. What is the significance of "23 hours and 56 minutes?" Know why you can't see some constellations at certain times of the year. Understand the significance of Polaris, the NCP, the SCP.

Chapter 4

Know Kepler's laws of planetary motion, and know what they mean. What is a period, a semimajor axis? Be able to describe Newton's laws of motion. State Newton's law of universal gravitation, and know how the strength of the gravitational force will change (qualitatively and quantitatively) if you change mass and/or distance. What is the distinction between mass and weight? How is weight related to Newton's law of universal gravitation? Explain how orbits work -- why do things orbit? Why don't they just collide with each other?

Chapter 5

What is the importance of the speed of light? Understand the definitions of wavelength of light, frequency of light, and energy of a photon -- and how they are related to each other. Know the range of wavelengths that your eye can detect, and how color corresponds to wavelength. List the seven types of electromagnetic radiation in order, and know their wavelength-ranges.

What are the three types of spectra (continuous, emission, absorption)? Under what circumstances are they produced (Kirchhoff's laws)? Define a blackbody, and understand how the light that it emits changes with temperature. Be able to draw the spectrum of a blackbody, and know how it changes with temperature. What is l_max, how does it change with temperature, and how is it related to the overall color of a blackbody? Understand what flux is, and how it changes with temperature.

Know the relationship between spectral lines (emission/absorption) and chemical composition. Be able to explain what causes emission/absorption lines, using the Bohr model of the atom. Know how to use the Bohr formula to calculate the wavelengths in the hydrogen spectrum. What is "the Balmer series?" Understand the Doppler effect, and be able to calculate radial velocity from the wavelength-shift of a spectral line.

Chapter 18

What is the source of the Sun's energy? What is converted into what? What does E = m c² have to do with it? (You do not need to know all the details in the step-by-step process of nuclear fusion, as depicted in Figure 18-2.) How hot must it be for nuclear fusion to take place, and why? Understand the principles of hydrostatic equilibrium and thermal equilibrium, and what they imply about the interior of the Sun. Why is the core of the Sun so much hotter than its surface? If the Sun's fusion reactions make gamma-ray photons, why aren't we all dead? Know what neutrinos are, and why they are important for studying the Sun. What is the solar neutrino problem?

Chapter 19

Know what parallax is, and how it is related to distance. Why can't we use the parallax technique on stars that are farther away than 1000 pc? Define luminosity and brightness, and know how these quantities are related to distance (the inverse square law). How will the brightness of an object change (qualitatively and quantitatively) if the object's luminosity is changed, or if the distance to the object is changed? Understand the spectral classification system (OBAFGKM), and know how it is related to temperature. Why does the strength of an absorption line depend on temperature? How is a star's luminosity related to its size and surface temperature?

You should know how to read an H-R diagram (luminosity, temperature, spectral type, radius). Where on the diagram would you find main-sequence stars, giants, supergiants, white dwarfs, the Sun? What is the relationship between luminosity and temperature for main-sequence stars? Know what luminosity classes are, and how you deduce them from a star's spectrum. What is the method of spectroscopic parallax, and how does it work?

Know how to use Newton's version of Kepler's Third Law to find the masses of stars in a binary system. (Don't worry about the distinctions between the different types of binary systems -- spectroscopic binaries, eclipsing binaries, et cetera -- that are discussed in the closing sections of Chapter 19.) Understand what the mass-luminosity relation is, and why it exists.