Astronomy 101: Understanding Celestial Bodies and Their Movements - Prof. Megan Donahue, Study notes of Physical Education and Motor Learning

Download Astronomy 101: Understanding Celestial Bodies and Their Movements - Prof. Megan Donahue and more Study notes Physical Education and Motor Learning in PDF only on Docsity! Visions of the Universe Final Exam Review Chapter 1 Earth: 150 million km from the sun Milky Way galaxy has 100 billion stars and is 100,000 light years in diameter Universe  Milky Way Galaxy is one of 100 billion galaxies  1022 stars Observable Universe = 14 billion light years Cosmic history: All of recorded human history = 30 seconds, 1 month = 1.2 billion years Almost everything in the universe rotates and orbits counter-clockwise Solar System is 28,000 light years from center of galaxy Galaxies move with the expansion of the universe  Almost all galaxies appear to be moving away from us  The farther away they are the faster they are moving away  Every point is receding from every other point no “center point” Measuring the rate of expansion of the universe gives the age of the universe Chapter 2 Constellation: region of the sky The stars appear to lie on a celestial sphere even though they are really at different distances The Celestial Sphere is divided into 88 Constellations The Milky Way in our night sky is actually our view into the disk of the milky way galaxy North Celestial Pole  above north pole Celestial equator  above equator South Celestial Pole  above south pole Objects position in sky is given by altitude and direction Latitude: position north or south of equator Longitude: position east or west of prime meridian Circumpolar stars never set Stars and everything rise in the east and set in the west Earth is closest to sun in January Earths orbit is nearly circular ellipse (distance not cause of seasons) Solstice: Time when difference between directness of sunlight between north and south is greatest Equinox: Time when directness of sunlight in north and south are equal Winter Solstice = December 21 Spring Equinox = April 21 Summer Solstice = June 21 Fall Equinox = September 21 Season changes are more extreme at high latitudes Precession causes Earth’s rotation axis to trace a circle in space over the course of about 26,000 years, because of this Earth’s position in orbit on a particular date slowly shifts “El Gordo” = cluster of galaxies We see different phases of the moon because our view of the side of the moon lit by the sun changes as the moon orbits earth, goes through one cycle of phases about 29.5 days = 1 month Moon Phases  New  Waxing Crescent  First Quarter  Waxing Gibbous  Full  Waning Gibbous  Third Quarter  Waning Crescent Mass = total amount of matter Weight = the force that gravity puts on an object Newtons Three Law 1. Object moves at constant velocity unless a force acts upon it 2. F = ma 3. For any force there is an equal and opposite force Conservation of Momentum  In any interaction, the total amount of momentum doesn’t change  Forces merely transfer momentum from one object to another Gravity constantly exerts forces between planets and sun keep the planets in orbit Angular momentum = mass x velocity x radius Conservation of Angular Momentum  In any interaction of total amount of angular momentum does not change  As radius decreases, spin velocity increases Kinetic Energy: energy of motion Potential Energy: stored energy Radiative Energy: energy of light Temperature Kelvins: temperature unit T ( in kelvin) is directly proportional to the random Kinetic Energy of the gas particles 273 K = 0 deg C, 0 K = -273 C0 The force of gravity between two objects depends on the product of their masses and the square of the distance between them Fg = G x ((M1M2)/d2) Escape Velocity: specifies the speed needed to escape an objects surface The shape of an orbit depends on the total amount of energy Kepelers Third Law is how we measure a mass P2 = (1/(M1 + M2)) x a3 Planets weigh much less than stars Planets mass is too tiny to change its orbit Chapter 5 A spectrum is a plot of light intensity vs wavelength 1. Light as a wave a. Wavelength: distance between peaks b. Frequency: the number of times per second the wave bops up and down ( 1 Hertz = 1 cycle per second ) c. Light interacts with magnetic and electric charges d. C = 300,000 km/sec, speed of light e. Wavelength x Frequency = C Remember order of Electromagnetic Spectrum 2. Light as a particle a. Photons: particles of light b. The higher the frequency higher the energy Elements and Atomic Structure  Elements are made of atoms  Atom ( charge ) o Protons + and neutrons (0) = Nucleus o Atomic # = # of protons o Atomic mass # = protons + neutrons o Isotope: same atomic #, different mass # o Ion: charged atom How do matter and light interact? 1. Emission 2. Absorption 3. Transmission 4. Reflection or scattering Transparent vs. Opaque  Transparent: transmits light  Opaque: blocks (absorbs or reflects) light What is color? An object reflects some wavelengths of light and absorbs, transmits, and emits others, what we see depends on our eyes and brain 3 basic types of Spectra 1. Continuous Spectrum, Thermal Radiation 2. Absorption line spectrum 3. Emission line spectrum How does light tell us what things are made out of? Electrons and light  Only photons whose energies match the change in electron energy levels are emitted or absorbed  With enough energy electron can escape atom completely  Only specific electron energies allowed  Absorption or emission happens at very specific energies Every atom, ion and molecule has its own unique spectral fingerprint How does light tell us what temperature things are? Thermal Radiation  All everyday objects emit it  Only transparent objects don’t emit it  Spectrum depends on temperature Light per are peaks shorter wavelength as energy increases Two Properties of Thermal Radiation 1. Hotter objects emit more light at all frequencies per unit area 2. Hotter objects emit photons with a higher average energy Temperature = Average Kinetic Energy Thermal Energy = total Kinetic Energy How does light tell us the speed of an object? The Doppler Effect  Conservation of Energy What’s the cause of inner rock planets and outer rock planets  Conservation of Energy Frost line: outside cold enough to form ices, inside too hot Accretion: gravity draws planetesimals together Asteroids Come from?  Leftover planetesimals Existence of moon: caused by collisions and impacts Nebular Theory Figure 6.24 Measuring elements in meteorites indicate age of solar system: 4.6 billion years (radioactive decay) Planet is 1 million to 1 billion times fainter than star We detect planets around other stars by looking for wobble of the star We measure the wobble using the Doppler shift in the star’s spectrum Doppler shift of wavelength: measures velocity “now” change in Doppler shift = change in velocity = acceleration The size of the velocity variation with time tells us the planets mass. Higher velocity difference = bigger planets mass Period (in years) of the wobble tells us the radius of the planets orbit, through Newton’s version of Kepler’s third Law, P2 = a3/(Msystem/Msun) Detect planets if they eclipse their star Fraction of starlight blocked tells us planets size Kepler Mission  Monitoring 100,000 stars for eclipses to search for Earth-sized planets for 4 years  0.01% variation  Two Earth-sized planets Over 687 known extrasolar planets Most are gas giants more massive than Jupiter and closer to their star than sun to earth  Stars and planets do form from interstellar gas clouds  The clouds do collapse under their own weight and form disks No interactions, planets don’t migrate Chapter 7 How do we predict climate change?  Computer models  Extrapolate trends on Earth  Study more worlds under extreme conditions  Wait and see what happens Planets as homes for life Mars once had flowing water  Mars appear to have ancient riverbeds  Eroded Craters, patterns of water  Low-lying regions may have had ocean What determines surface temperature?  The energy emitted by a planet in infrared light equals the amount of sunlight energy it absorbs, Conservation of energy  Daily variations in temperature depend on a planets rotation rate  The intensity of sunlight on a planet depends on its distance from the sun Planets Reflectivity affect temperature, what energy is not reflected is absorbed Greenhouse effect  Earth’s atmosphere absorbs light at most wavelengths  Figure 7.15 molecules let visible light through but absorb infrared photons  Certain molecules let sunlight through but trap escaping infrared photons Mars once had a thicker CO2 atmosphere, dramatic climate change 3 billion years ago Mars interior cooled off, lost its magnetic field, atmosphere lost to stripping by early solarwind Venus  Thick CO2 clouds Earth’s CO2 is in plants, rocks, and ocean CO2 dissolves in ocean and gets locked into rocks A runaway greenhouse effect would occur if Earth was at Venus distance from sun Earths Climate changes CO2 content of Earth’s atmosphere is steadily increasing. The rate of increase and the CO2 level are both higher now than at any time in the last 400,000 years Increased CO2 is causing global warming: causation established by comparing the model predictions to data The excess carbon is from humans  Rate we produce CO2 is greater than ocean can absorb Even if we make changes today, the effects are not felt by the climate for a long time, delay because CO2 sticks around ‘Runaway Greenhouse Effect, occurs when a planet absorbs more energy from the sun than it can radiate back to space. Under these circumstances, the hotter the surface temperature gets, the faster it warms up. Scientists detect the signature of a runaway greenhouse when planetary heat loss begins to drop as surface temperature rises. Read Chapter 9.3 Chapter 9 What do asteroids look like?  The streaks are curved because of parallax caused by Earths orbit  Not round, have craters Meteroid: chunk of rocks Meteor: bright tail A stars mass and age determine its other properties - Know stellar evolution stories for low and high mass stars High mass star > 8 solar masses Low < 8 Solar masses Brown Dwarfs: Electron Degeneracy pressure During red giant phase and double shell red giant star is increasing in size Big Bang produced H and He Star production produced everything else Supernovas – everything heavier than iron Fe has lowest mass per nuclear particle Early Universe must have been very hot and dense, as universe expands collisions become cooler/less energy Know ERAS Four Fundamental Forces (unify as one at high enough energy) 1. Strong 2. Electro-magnetic 3. Weak 4. Gravity Helium/Hydrogen ratio and Cosmic background evidence for Big Bang The final is cumulative: review your midterm results at least once! Look particularly hard at the questions you got wrong and at the questions you guessed right (a lucky guess may not be so lucky on the final). Questions from each midterm will be repeated on the final either verbatim or in a very slightly different form - be sure to read the questions carefully. Don't assume they are exactly the same. Use the exam reviews on Mastering Astronomy to review practice exam questions. The clicker questions are often inspirations for exam questions; lectures identify the important ideas. Note that answers to the "quick quiz" questions at the end of the chapter are available in the Mastering Astronomy exam reviews. There will be no more than 70 multiple choice question on the final. About 10-15 questions will come from Chapters 16, and the rest will be from Chapters 1-15 and Chapter 17, excluding Chapter 8. There will be one optional essay question. It will be graded if your computed Course Grade lies on the border between two grades. For example, if your course grade after the final exam is 89.5, the decision as to whether you get a 4.0 or a 3.5 lies in how well you wrote your optional essay. If it shows me you deserve a 4.0, your grade gets rounded up. Otherwise, it remains a 3.5. You have to take the final exam and write an essay to have this opportunity. All students who opt not to take the final should expect to get whatever their Interim Grade was, which I will compute and post on April 27. For example, an 89.7 will be a 3.5 in that situation. If you want an opportunity to improve the interim grade, take the final. FINAL EXAM review questions for Ch. 16. Relevant review questions for the final: Ch. 16 End of chapter questions 1-3, 5-8, 10-36. Ch. 17 The topic of deuterium abundance and normal matter will appear on the final exam (it wasn't covered on Exam 3). The cosmic calculation 14.1 (orbital velocity law, p. 391) is relevant to understanding the evidence for dark matter. If the math was on a previous exam (example: luminosity-brightness-distance relation) it may be required on the final exam. The cosmic context figures (e.g. Figure 16.17, 17.5) should be extremely useful in identifying and summarizing the major ideas from these chapters. Work through the Visual Skills Check (p. 469 and 497). The answers are in the back of the book. Figure 17.12 (covered in the Visual Skills Check for Ch 17) is challenging, but if you succeed in figuring out what it is trying to tell you, you will understand how the deuterium to hydrogen ratio measurements limit the amount of normal matter there can possibly be in the universe. Here is the chapter 16 slides that will be important for the final. I believe 10 questions from this chapter will be on the examhttps://angel.msu.edu/section/default.asp?id=SS12-ISP-205-002-937765-EL-32-381