Astro 4 - Key Themes in My Test Bank

This is a generic list. I made this by looking at all the ~ 400 questions in my test bank. Remember that I make my quizzes and finals fresh each semester, and you'll see roughly 120 questions drawn randomly from this master test bank. For more help in studying for your particular questions, refer to the study guide I handed out and which is on-line for the Monday/Wednesday, and for the Monday evening classes, which focuses in a different way on your particular exams. Looks like a lot to learn here, right? But before you get depressed, realize that your particular exams will only sample a small part of this, and all you need is a 75% for an "A". You can do it!

Chap 0: Scientific Thinking

• All of “Chap 0” is important! Read it thoroughly and ask for any clarifications
• The steps of the scientific method
• The nature and psychological issues of pseudo-science.
• Occam’s Razor
• Modes of representing reality in our minds
• The fatal flaws with supernaturalism

Our Place in the Universe

• Most of this material we will cover in more detail later so I have not written questions on it. But, I do have a few introductory ideas for you to focus on
• Distances; definition of a light year, the general distance order of things out there; planets, stars, galaxies.

Universal Motion, Relativity

• Know Kepler’s 3 laws and their meaning
• Know Newton’s Laws of Motion and their meaning
• Tides as more than water at the beach – the cause of tides via gravity and what aspects of a gravitating system will increase or decrease tidal force
• Spring tides and neap tides and how they relate to the position of sun, moon.
• The meaning of angular momentum and conservation of angular momentum

Light, Energy

• Photons as electromagnetic waves in a particle form
• The two ways to produce photons.
• The electromagnetic spectrum and the names of the different energy or wavelength bands in the spectrum. Which bands will pass through earth’s atmosphere.
• The structure of the atom: nucleus and electrons in quantized orbits. Don’t memorize the names of atoms and how many protons! I want concepts.
• Emission and absorption of photons via electrons changing orbits in atoms, and how these processes make the spectral “lines” in astronomical objects.
• Absorption lines: produced by cool gas in front of a hot object
• Emission lines: produced by gas lit up from the side against a black background.
• The Doppler effects; photons “redshifted” to longer wavelength if source / observer are moving apart; “blueshifted” if moving towards each other
• Know the shape of a thermal spectrum, and the two thermal radiation laws: Hotter objects are bluer. Hotter objects give off more total light.
  

Relativity

• Special Relativity follows from the fact that the speed of light in a vacuum is measured to be the same no matter how the observer is moving
• General Relativity follows from the Equivalence Principle: Effects of gravity are identical to the effects of being in an accelerating coordinate frame.
• General relativity = modern gravity; paths follow curvature of space, determined by mass and energy density.

The Sun

• The structure of the sun; layers, temperatures, densities, and why
• The cause and nature of sunspots
• The basics of nuclear fusion; hydrogen into helium, electromagnetism

vs. the strong nuclear force

• Neutrinos – tiny interaction rate with other matter, the solar neutrino problem
• Stars – balancing gravity, energy production, pressure. How changing one will affect the structure of the star
• Aurorae; relation to the solar corona, magnetic fields
• The 3 mechanisms of heat transfer and which dominate in which layers of the sun

Properties of Stars and How We Measure Them

• Parallax; know how we measure it to determine distances to stars
• The H-R Diagram main features; main sequence, red giants, white dwarfs
• Mass – luminosity relation for main sequence stars
• Spectral types – really a temperature sequence. Hotter stars have fewer absorption lines. Know the sequence!
• Fusion – all main sequence stars burn hydrogen into helium in their core
• Understand eclipsing binaries; allow measurement of most stellar properties
• Stellar demographics; most stars are low mass, but a brightness-limited sample will be dominated by high mass stars – they’re far more luminous

Star Formation and Evolution

• Know the mass limits for a star and why
• The 2 “fuel tanks” of a star; gravitational potential energy, and fusion
• Star formation requirements; high density and low temperature, shock waves
• Brown dwarfs – too little mass to allow core fusion
• Stars always born in star clusters, how age of a cluster determined
• Know the evolutionary sequence of a low mass star, medium mass star, and high mass star, and relative lifetimes for each
• Cepheids; pulsating stars which change their brightness
• Supernovae – know the two types; ‘carbon bomb’ and iron core, and why
• Know iron core supernovae produce all of the elements in the universe heavier than iron
• Know the nuclear energy curve; which nuclear reactions produce, and which consume, energy. This determines the evolution of stars.

The Stellar Graveyard

• Novae; fusion explosions on the surface of binary star white dwarf
• Supernovae type I = “carbon bomb” supernovae. Know why
• Know the 3 end states of a star - white dwarf, neutron star, black hole – and the mass limits of each
• Know the typical sizes of white dwarfs, neutron stars, and black holes
• Know pulsars; flashing lights in the sky due to rapidly spinning neutron stars

Our Milky Way Galaxy

• Spiral arms – density waves sweeping through the interstellar medium initiating star formation
• Globular vs. open star clusters; their different ages and origins, and where they are in the galaxy
• Stellar populations: the definition, explanation, and distribution of Pop I vs. Pop II
• Know the evidence for a massive black hole in the center of our galaxy
• Know the structure; disk, bulge, halo, nucleus, dark matter
• Sun is (vertically) centered in the disk, where dust is concentrated. Affects our ability to see the rest of the galaxy
• Know the prime evidence for dark matter in our galaxy
• Galaxy formed from agglomeration of smaller proto-galaxies soon after Big Bang

Galaxies, Galaxy Evolution

• Cepheid variables and period/luminosity relation; importance in measuring galaxy distances, sizes
• The general star formation history; in spirals vs. ellipticals
• Like stars, most galaxies are low mass and low luminosity, but brightness-limited photographs will be dominated by large galaxies – spirals and giant ellipticals
• Structure of Ellipticals; how determined by observing twisted isophotes
• Galaxy collisions -> irregulars, more common in early universe when it was more crowded
• Know the Hubble Law and its uses and pitfalls in measuring distances to galaxies, and in estimating the age of the universe
• The distance ladder: different methods have to be pieced together in order to measure the distances across the universe
• Light travel time, how it allows us to study the early universe

Dark Matter

• How we measure mass in galaxy clusters and star clusters using velocity dispersion
• We don’t know exactly what it is, but we’ve ruled out all ordinary forms of matter. Know what class of material it must be
• Cold Dark Matter vs. Hot Dark Matter, which is the dark matter? Why?
• MACHO Collaboration has ruled out all dark matter candidates the size of planets or larger.
• What the rotation curve of a galaxy is; used to determine the mass distribution, and evidence for an extended dark matter halo around all galaxies

Cosmology

• Why only hydrogen and helium emerged from the cooling matter after the Big Bang
• Know difference between the “universe” and the “observable universe”
• Know evidence that the Big Bang really happened; CMB, abundances of the elements
• CMB: redshifted light from the time when hydrogen , helium cooled from ionized to neutral.
• The “cosmological constant” and relation to the acceleration of the expansion of the universe; it dominates the mass/energy density of the universe. Know what current observations support it.
• Know Olber’s Paradox – proof that the universe can’t be both eternal and infinite
• Know the basic idea of “inflation”. Postulated to solve what problem in the “standard” Big Bang? New evidence strongly supports it really happened.
• Matter and anti-matter in the early universe, and how ratio is preserved in the CMB

Life in the Universe

• The Miller-Urey experiment created amino acids out of the chemistry, conditions of the early Earth
• G, K main sequence stars most likely to have living planets
• Carbon – the only element permitted by the laws of physics which can be used to make complex molecules, why needed for life.
• The arguments for searching for radio communications near the main spectral lines for water
• theories of the origin of the Big Bang also predict a near-infinite number of alternate universes; if so, we are self-selected to be a univers suitable for life. This kabosh's the supernatural argument.