Astronomy 1: Stars and Black Holes Final Exam Study Guide 2024 PDF

Astronomy 1: Stars and Black Holes Final Exam (Dec 12, 2024) Study Guide The final will consist of 105 questions (20 True/False and 85 multiple choice). You will have 180 minutes (3pm-6pm) to complete the exam. The exam will cover all cont...

Astronomy 1: Stars and Black Holes Final Exam (Dec 12, 2024) Study Guide The final will consist of 105 questions (20 True/False and 85 multiple choice). You will have 180 minutes (3pm-6pm) to complete the exam. The exam will cover all content covered in the course. The questions will be very similar in style to your HW problems and to the first two midterms. I will provide each of you with an equation sheet (this is posted on Canvas under Files for your reference). I am including below a list of topics that may be helpful to review. Good luck studying! Chapter 1: - Relative sizes and scales of different objects in the universe. Galaxy versus solar system versus stars versus planets. - Key units of distance in astronomy. Light-year versus AU versus solar radius. How are each of these units defined? - Age of the universe, age of the solar system, age of the earth. - How are elements made in the universe? Which elements were made in the big bang itself? Chapter 2: - Key concepts and terms related to the celestial sphere. Ecliptic, zodiac, constellations, north/ south celestial pole. - How do objects move across the night sky? How is this determined by the earth’s rotation? Which way does the earth rotate around its axis? Which way does earth orbit around the sun? - Understanding declination and right ascension. - How does the position of the sun change in the sky at the solstices and equinoxes? - How does your latitude affect the apparent altitude of the North Star? - What causes season’s on Earth? Chapter 3: - Understand the difference between geocentric and heliocentric models of the universe. What were the key scientific discoveries that led to the “Copernican Revolution”? - Kepler’s three laws of planetary motion - What causes retrograde motion of planets? - Understand the key concepts of the Scientific Method. What is the difference between a hypothesis, a law, and a theory? What is the process that goes into development of laws and theories in science? Chapter 4: - Understand difference between mass and weight - Newton’s three laws of motion - Newton’s theory of gravity. How does the force of gravity between two objects change as you change the object’s masses and their distance? How does gravity relate to acceleration? - Understand the relation between force and acceleration (Newton’s second law) - What causes tides on Earth? - What is difference between velocity and speed? How does velocity relate to acceleration? - Understand conservation of energy, momentum, and angular momentum. How are each of these terms defined? - Understand different types of energy: Kinetic energy, potential energy, radiative energy. Chapter 5: - Understand key properties of waves. How are wavelength, frequency, and wave speed related? For light, the speed of the wave is constant. - How is color related to frequency for light? What determines the color of a particular object that we see (for example, a rose?) - Understand the differences between emission, absorption, transmission, reflection, and scattering of light. - Understand the different parts of the electromagnetic spectrum. X-rays, ultraviolet, visible, infrared, radio, etc. - How does the wavelength and frequency of a photon relate its energy? - Understand the basic structure of matter. Understand what is a proton, neutron, electron, nucleus, atom, molecule, isotope, and ion. What is difference between atomic number and atomic mass number? - Understand electron energy levels of an atom and how these produce absorption/emission lines. - Phases of matter: solid, liquid, gas, plasma. Understand the differences and how changes in temperature and pressure cause changes in phases of matter. - What is difference between thermal spectrum, emission spectrum, and absorption spectrum? - How does light teach us about the temperature of stars? How does light teach us about what elements stars are made of? How does the color of a star tell us about its temperature? - What is a black body? Understand the two laws of thermal radiation. - How do we use the Doppler Effect to learn the velocity of an object? What is difference between redshift and blueshift? Chapter 6: - Understand the differences between refracting and reflecting telescopes. How does each type focus light? - How do light-collecting area and angular resolution impact what a telescope can see/resolve? - Understand the three main ways astronomers use telescopes: imaging, spectroscopy, time monitoring. - Why do we put telescopes in space? How does Earth’s atmosphere affect ground-based observations? Which types of light can successfully pass through Earth’s atmosphere? Which types are nearly entirely blocked? How do adaptive optics help overcome the atmosphere challenges? - How are X-ray and gamma-ray telescopes different from typical optical telescopes? Why are these telescopes designed differently? - Understand other types of cosmic messengers: gravitational waves, neutrinos, cosmic rays. Chapter 14: - Understand the key process that powers the sun. - How old is the sun? How does the sun’s age rule out chemical burning and gravitational contraction as possible power sources for the sun’s luminosity? - Understand the concepts of gravitational equilibrium and energy balance. How do these connect to sun’s evolution? Understand the concept of the “solar thermostat.” - Understand the key components of the sun’s structure, including its interior and its atmosphere. What are the different temperatures of these different regions? - How does nuclear fusion occur in the sun? Understand the basic of the fusion process (the proton-proton chain). - How does fusion energy escape from the sun? How long does it take energy to pass through the radiation zone? The convection zone? - How do neutrinos tell us about the interior of the sun? Why are neutrinos so difficult to detect? Explain the solar neutrino problem. - What causes solar activity? Understand sun spots, solar flares, prominences, and coronal mass ejections. - How long is the sunspot cycle? What causes the sunspot cycle? Chapter 15: - How do we measure stellar luminosities? What is the difference between apparent brightness and luminosity? How are these two quantities related (inverse square law for light) - Understand the basics of the magnitude system. For example, if three stars have apparent magnitudes +3, -4, and +11, rank these three stars in order of their apparent brightness. - Understand how stellar parallax is measured. How does stellar parallax tell us the distance to stars? - How do we measure stellar temperatures? Connect stellar temperatures to the two laws of thermal radiation. - Understand the sequence of spectral types of stars: OBAFGKM (you should know this order!) - What spectral type is most common? What spectral type is rarest? - Understand roughly the stellar masses corresponding to each spectral type. What spectral type is the sun? - Who were the key women astronomers (the Harvard computers) who helped discover the spectral sequence of stars? What is the origin of this spectral sequence? How does the spectrum of a star relate to its temperature? Why do hotter/cooler stars have different spectral lines? How does this connect to a star’s ionization level? Why do cool stars have molecular bands in their spectra? - How are stellar masses measured? What are the three types of binary stars (visual, spectroscopic, eclipsing)? Understand the differences between each of these. - How do we use Kepler’s third law to measure the mass of stars in binaries? - Understand the key features of the Hertzprung-Russell (HR) diagram. You should be able to identify the main sequence, giants/supergiants, and white dwarfs. - How are giant stars and white dwarfs different from main sequence stars? Are the bigger/ smaller? Hotter/cooler? Higher luminosity/lower luminosity? - Understand the features of the “main sequence.” What can the position of a star on the main sequence tell us about its luminosity, mass, temperature, spectral type, age, radius? - Understand the two types of star clusters — open clusters and globular clusters. - How do we measure the age of a star cluster from its H-R diagram? Chapter 16: - Why are dense and cold molecular clouds the ideal region of the interstellar medium for stars to form? - What is interstellar dust and what is it made of? Explain how dust makes molecular clouds opaque to visible light. - Understand how dust in molecular clouds prevents visible light from passing through. Molecular clouds are best observed using infrared telescopes. - Understand the key steps in star formation. Gravity overcomes outward push of thermal pressure in the cloud. What is a protostar and how is a protostar different from a main- sequence star? - What is role of rotation in stellar birth? Understand the key components: protostellar disks, jets, and protostellar winds. - Understand the basic path of a protostar on the H-R diagram. When and how does nuclear fusion eventually start in the protostar center? - What is the smallest mass star that can form? Why can’t nuclear fusion support stars with masses below 0.08 solar masses? Understand how degeneracy pressure supports these low- mass brown dwarfs from collapse. - What is the highest mass star that can form? Explain how radiation pressure prevents formation of stars much above 150 solar masses? - How would the mass range of stars be different for the first stars formed in the very early universe? These are called “Population III” stars and would contain only hydrogen and helium? Have these stars ever been observed? - What are the typical masses of newborn stars? Are low mass or high mass stars more common? By how much? - Do high mass stars or low-mass stars for more quickly? Why? Chapter 17: - How does star’s mass affect nuclear fusion in its center? Understand how more massive stars have hotter cores, allowing fusion to proceed more quickly. - Understand the differences in evolution between low-mass stars (masses below 2 solar masses), intermediate mass stars (masses between 2-8 solar masses), and high mass stars (masses above 8 solar masses). - Understand the differences in structure of low-mass and high-mass stars. Where are the convective and radiative zones in main-sequences stars of different masses? - Understand the key stages in evolution of low-mass stars: main-sequence, red giant (hydrogen shell fusion), helium flash, helium fusion star, planetary nebula, white dwarf. Why don’t low- mass stars ever undergo carbon fusion? Understand the location of each stage on an H-R diagram. - Understand the CNO cycle and why this is important for higher mass stars. - Explain the “onion layer” model of high mass stars and why this structure arises from nuclear fusion of increasingly heavy elements in the star’s center. - Why is the element iron important in evolution of massive stars? Why can’t iron fusion release energy? What happens when the iron core of a star ultimately collapses? - What is the role of neutrinos in supernova explosions? - Understand the two main types of supernovae: white dwarf supernovae (Type I) and massive star supernovae (Type II). Type I contain no hydrogen in their spectra, Type II contain hydrogen — why? - Have supernovae been observed historically? What was the most recent nearby supernova explosion (1987A) and why was it important? - Understand how the evolution of stars can be different in binary star systems. How can mass exchange between stars effect their lifetimes? Chapter 18: - Understand the three types of stellar remnants: white dwarfs, neutron stars, and black holes. - Explain how electrons degeneracy pressure supports white dwarfs against collapse. - What masses of stars will ultimately end their lives as white dwarfs? What is the ultimate fate of the Sun? - Understand the typical sizes and masses of white dwarfs. What is the highest mass possible for a white dwarf (roughly 1.4 solar masses). Explain how this maximum mass relates to electron degeneracy pressure. Why are more massive white dwarfs smaller in radius? - Explain how white dwarfs found in binary systems can undergo nova eruptions and, in some cases, white dwarf supernova explosions. - What is the typical size and mass of a neutron star? Explain how neutron degeneracy pressure supports these objects from collapse. What is the maximum mass of a neutron star? - Understand how a pulsar is a rapidly-rotating neutron star. Where does this extremely rapid rotation come from (conservation of angular momentum during stellar collapse). - What can happen to a neutron star in a binary system? Understand X-ray binaries and X-ray bursts. - Explain why a black hole is “black.” - Understand the terms event horizon and Schwarzschild radius for black holes. - Why does time run more slowly near the event horizon of a black hole? Explain the basic concept of “gravitational time dilation” form the general theory of relativity. - What causes gamma-ray bursts? How can observed gamma-ray bursts tell us about formation of black holes? - Understand how merging neutron star pairs and merging black hole pairs emit gravitational waves. Understand some neutron stars mergers can produce gamma-ray bursts. S2/S3: - Understands the two major absolutes of the special relativity: (1) Laws of nature are same for everyone, (2) speed of light is same for everyone - What is “relative” about the theory of relativity? (motion) - Why can’t we reach the speed of light? - How does relativity affect our view of space and time? Explain how relativity implies objects moving near the speed of light experience time dilation and length contraction. - What is the major different between general and special theory of relativity? (general relativity includes gravity) - Understand the “equivalence principle” and how this relates gravity to acceleration - Understand “spacetime” as a four-dimensional combination of the three spatial dimensions and one time dimension. - Understand how the general theory of relativity explains gravity as curved spacetime. - Explain how a black hole is a “bottomless pit” in spacetime, or a “hole” in spacetime. - Explain gravitational time dilation for objects within a gravitational field. Explain how gravitational time dilation is different near a black hole compared to near Earth?