Principles of Astronomy: Possible Topics J. M. Veal, Ph. D. version 20.03.03 Contents 5 Solar System 19 5.1 Overview of Solar System Objects . 19 1 Introduction 2 5.2 Space Exploraton: Past & Present . 19 1.1 Cosmic Perspective . .2 5.3 Aurora Borealis . 21 1.2 Nature of Science . .3 5.4 Introduction to Terrestrial Planets & K ...... 21 5.5 Interiors of Terrestrial Planets & K ......... 21 2 Basics 4 5.6 Surfaces of Terrestrial Planets & K ......... 22 2.1 Sky Coordinates . .4 5.7 Atmospheres of Terrestrial Planets . 22 2.2 Earth's Rotation . .4 5.8 Mythology of Terrestrial Planets in Brief . 23 2.3 Precession . .4 5.9 Introduction to Jovian Planets . 23 2.4 Appearance of Stars . .4 5.10 Atmospheres of Jovian Planets . 23 2.5 Seasons . .4 5.11 Interiors & Magnetic Fields of Jovian Planets . 23 2.6 Lunar Phases . .5 5.12 Mythology of Jovian Planets in Brief . 24 2.7 Days & Months . .5 5.13 Moons . 24 2.8 Eclipses . .5 5.14 Rings . 24 2.9 Retrograde Motion . .5 5.15 Dwarf Planets . 24 2.10 Kepler's Laws of Planetary Motion . .6 5.16 Asteroids & Comets . 25 2.11 Newton's Laws of Motion . .6 5.17 TNO's . 26 2.12 Newton's Universal Law of Gravitation . .6 5.18 Meteors . 26 2.13 Tides . .6 6 Stars 26 3 Fundamental Concepts 7 6.1 Star Formation in Brief . 26 3.1 Electromagnetic Radiation in Brief . .7 6.2 Star Formation . 26 3.2 Electromagnetic Radiation . .7 6.3 Nuclear Fusion . 27 3.3 Observing Instruments & Techniques . .7 6.4 Limb Darkening . 28 3.4 Temperature . .8 6.5 Sunspots in Brief . 28 3.5 Thermal Radiation . .8 6.6 Sunspots . 29 3.6 Scattering . .8 6.7 Stellar Evolution & the H-R Diagram . 29 3.7 The Classical Atom . .8 6.8 Life of Our Sun . 30 3.8 Quanta, Absorption, & Emission . .9 6.9 Supergiants & Supernovae . 31 3.9 Spectral Lines . .9 6.10 Neutron Stars & Pulsars . 32 3.10 Ionization, Recombination, & Cascade . 10 6.11 Binary Stars . 32 3.11 Collisional vs. Radiative Processes . 10 6.12 Novae . 33 3.12 Magnetic Fields . 10 6.13 Cosmic Recycling . 33 3.13 Doppler Shift . 10 3.14 Parallax . 11 7 Galaxies 33 3.15 Proper Motion & Radial Velocity . 11 7.1 Overview of Galaxies . 33 7.2 AGN . 33 4 Physical Principles 12 7.3 Dark Matter . 34 4.1 Special Relativity . 12 4.2 Duality Of Light . 13 4.3 Uncertainty Principle . 14 4.4 Quantum States . 16 4.5 Exclusion Principle . 17 4.6 Matter & Antimatter . 17 4.7 Arrow of Time . 18 1 J. M. Veal, Principles of Astronomy 2 8 Black Holes & Cosmology 34 1 Introduction 8.1 Early Universe . 34 8.2 Curved Spacetime . 35 1.1 Cosmic Perspective 8.3 General Relativity . 36 What is large? What is small? Consider walking from San 8.4 Black Holes in Brief . 36 • Diego to Los Angeles. An example of a scale model is a 8.5 Black Holes . 37 globe. Perhaps the scale is 1 inch = 1000 miles. 8.6 Gravitational Redshift . 39 8.7 Hubble's Law & Hubble Distance . 39 Solar System. 8.8 Cosmological Redshift . 39 • What is the solar system? For now, let's say Sun, planets, 8.9 Big Bang . 40 moons, asteroids, & comets (no other stars!). (\My Very 8.10 Cosmic Microwave Background . 40 Excellent Mother Just Served Us Noodles.") 8.11 Hubble Parameter & Observable Edge . 40 8.12 Cosmic Horizon & Dark Energy . 41 The scale is 1:1010. (In astronomy we use scientific notation 8.13 Fate of the Universe . 42 for large numbers.) No units are needed because they're the same on both sides. (A person would be 107 miles tall in 9 Life in the Universe 42 this model.1) 9.1 Interstellar Chemistry . 42 The relative sizes are easy to show in a book or on a screen, 9.2 Comets . 43 as are the relative distances. [sketches 1 & 2] But showing 9.3 Search for Extrasolar Planets . 44 both the relative sizes and distances in the a single scale 9.4 Origin of Life . 44 model can't be done in a book or on a screen. Could we 9.5 Nature of Life . 45 walk to α Centauri, 4.4 light years away? 9.6 Definitions . 45 9.7 Possible Existence of Extrasolar Intelligence . 46 Milky Way. 9.8 Search for Extraterrestrial Intelligence . 46 • What is the Milky Way? It's our galaxy, full of stars, dust, 11 10 Miscellaneous 47 & gas. There are more than 10 stars in our galaxy. How 10.1 Pseudoscience . 47 much is a hundred billion? (Consider salt in Qualcomm...) 10.2 Exam Instructions & Answer Sheet . 48 The scale is 1:1019. Or, 1 mm = 1 light year. (A light year is the distance light travels in one year, roughly equal to 1013 km.) Or, atom-size = star-size. In this model, our Milky Way would be the size of a football field { with the Sun at about the 20 yd. line. Alternate Milky Way model. • If the d is a grain of NaCl, the next grain is 7 miles away. This model is useful when visualizing galaxy collisions. Universe. • The universe is everything that exists. There are more than 1011 galaxies in the universe. Ñ 1022 stars. How much is 1022? (Consider grains of sand... ) In astronomy, it's not acceptable to confuse the solar system, • the galaxy, and the universe.2 Time. • Now the scale model is 1 year = age of universe. (The age of the universe is about 13.8 billion years.) January 1: big bang (the beginning of space, time, matter, energy, force, ...) February: Milky Way forms September 3: Earth forms September 22: earliest life on Earth December 26: rise of dinosaurs December 30: extinction of dinosaurs Dec. 31, 9 p.m.: earliest human ancestors 1Model sizes in mm for the Sun and 8 planets are as follows: 139, .5, 1.2, 1.3, .7 14.3, 12.0, 5.2, and 4.8. Model distances in m from the Sun to the 8 planets are as follows: 6, 11, 15, 23, 78, 143, 287, and 450. 2htwins.net; The Known Universe by AMNH; cosmic eye; atlasoftheuni- verse.com; Cosmic Voyage. J. M. Veal, Principles of Astronomy 3 Dec. 31, 11:58 p.m.: first modern humans { R. Descartes? What can we be absolutely sure of? Dec. 31, 11:59:25 p.m.: rise of agriculture Might we be dreaming? He says cogito ergo sum, and that we can be sure of it. His argument appeals to our Dec. 31, 11:59:49 p.m.: pyramids at Giza intuition and common sense, but these cannot be relied Dec. 31, 11:59:59 p.m.: Kepler, Galileo upon in these matters. (Consider \eivocae"...) Motions. • Science seeks to describe what we observe, to find patterns, How does Earth move? Like a top on a record player on a • and to make subsequent predictions. (Consider learing grav- merry-go-round. ity...) motion speed period rotation 600 mph 1 day When evidence contradicts a theory, the theory must be precession 26,000 yrs • changed or dismissed in favor of a new theory. (Consider revolution 60,000 mph 1 year a helium balloon...) galactic orbit w/ \bounce" 600,000 mph 230 ¢ 106 yrs Milky Way toward Andromeda 180,000 mph Science seeks to explain these patterns with the simplest • expansion of universe v H0r answer (like Ockham's Razor). Reading. What does simple mean3 and what is a simple theory? To • answer this, we must consider the number of initial condi- { TCPF2: Chapter 1, Sections 1 - 2. tions needed for the theory to happen (like the ingredients in a recipe) and the number of characteristics or parts of the Homework. • theory (like the steps in a recipe). 1. (3 points) List the eight planets in order of increasing distance from the Sun. { Consider a statement that describes a wrinkled piece of 2. (5 points) Planet A is roughly how many times further paper. How many statements are necessary to describe from the Sun than the Earth is? (Planet A can be any the chalk completely and exactly? One for the velocity of the seven other planets.) and position of every electron, proton, neutron, etc. We see that even a piece of chalk is far from simple. 3. (8 points) Consider our scale model of the solar system. (Simple: photon(1), black hole(3).) How far would we have to walk to reach the d's near- est neighbor, α Centauri? (To answer this question, { Consider an example in which science must choose, you must set up the appropriate ratio and solve for the based on simplicity, between two theories. (Neither can correct quantity.) be proven; neither can be disproven.) A) The universe was created 5 minutes ago with all of our memories in 4. (8 points) Consider our two visualized models of our tact { far from simple. B) The big bang theory { simple galaxy, the Milky Way. In the first, stars were the size compared to A. of an atom, α Centauri was 4.4 millimeters from the d, and the galaxy was 100 yards across. In the second, Further lines of thought include the following. stars were the size of a grain of salt, α Centauri was • 7 miles from the d, and our galaxy would be how far \Absence of evidence isn't evidence of absence." across? (To answer this question, you must set up the \What cannot be settled by experiment is not worth debat- appropriate ratio and solve for the correct quantity.) ing."4 5.