Astronomy 162 - Stars, Galaxies, & the Universe Serial http://www.astronomy.ohio-state.edu/~pogge/Ast162/ en-us 2006-2026 Richard W. Pogge Richard Pogge Astronomy 162, Stars, Galaxies, and the Universe, is part 2 of a 2-quarter introductory Astronomy for non-science majors taught at The Ohio State University. This podcast presents lecture audio from Professor Richard Pogge's Winter Quarter 2006 class. All of the lectures were recorded live in 1008 Evans Laboratory on the OSU Main Campus in Columbus, Ohio. no Richard Pogge pogge.1@osu.edu mkitem.pl v0.2.1 Sun, 06 Dec 2009 00:00:00 EST Wed, 06 Mar 2013 13:17:52 EST Richard Pogge Welcome to the Astronomy 162 Lecture Podcasts! This is a brief message from me explaining the podcasts, and welcoming new and old listeners. Recorded 2006 Mar 10 on the Columbus campus of The Ohio State University. Ast162_Wi06_1142015676 Fri, 10 Mar 2006 13:34:36 EST astronomy, podcasting, education Richard Pogge Where are Lectures 1-4? This is a good question, and one I've gotten from many listeners. Here's the answer. Recorded 2006 Nov 27 on the Columbus campus of The Ohio State University. Ast162_Wi06_1164648050 Mon, 27 Nov 2006 12:20:50 EST astronomy, podcasting, missing lectures Richard Pogge How do we measure the distances to the stars? This lecture introduces the method of trigonometric parallaxes and the units of the Parsec and Light Year. Recorded 2006 January 9 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1136837600 Mon, 09 Jan 2006 15:13:20 EST astronomy, stars, distances, parallaxes Richard Pogge The "fixed stars" are really in constant motion, but these motions are too small to see with the human eye in a human lifetime. This lecture introduces proper motions (apparent angular motion of the stars in the sky), radial velocities (motion towards or away from us measured using the Doppler Shift of the star's spectral lines), and true space velocities, measured by combining three key observables: the proper motion, radial velocity, and distance to the star. Recorded 2006 January 10 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1136912492 Tue, 10 Jan 2006 12:01:32 EST astronomy, stars, motions, proper motion, radial velocity, space velocity Richard Pogge How do we quantify stellar brightness? This lecture introduces the inverse square-law of apparent brightness, the relation between Luminosity and Apparent Brightness, introduces the stellar magnitude system, and discusses photometry and the how we measure apparent brightness in practice. Recorded 2006 January 11 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1136996148 Wed, 11 Jan 2006 11:15:48 EST astronomy, stars, brightness, magnitude system Richard Pogge How do we measure the masses and radii of stars? This lecture describes the three basic types of binary stars, and how each are used to measure the masses of stars. Details of how to measure stellar radii are beyond the scope of this class, but we briefly describe the direct measurements of stellar radii. Recorded 2006 January 12 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1137082357 Thu, 12 Jan 2006 11:12:37 EST astronomy, stars, stellar masses, stellar radii, binary stars Richard Pogge What do the spectra of stars look like, and what can they tell us about stellar properties? This lecture introduces the idea of stellar color, gives a brief overview of the history of stellar spectroscopy, and introduces spectral classification and the main stellar spectral types OBAFGKMLT. Recorded 2006 January 13 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1137166352 Fri, 13 Jan 2006 10:32:32 EST astronomy, stars, spectra, spectral classes Richard Pogge How are all of the observed properties of stars (Luminosity, Mass, Radius, Temperature and Spectral Type) related to one another? This lecture introduces the Herzsprung-Russell Diagram, a plot of Luminosity versus Temperature for stars that is our most powerful tool for unlocking the secrets of the stars. Recorded 2006 January 17 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1137516857 Tue, 17 Jan 2006 11:54:17 EST astronomy, stars, Herzsprung-Russell Diagram Richard Pogge What are the physical laws that determine the internal structure of stars? We first introduce the Mass-Luminosity Relation for Main Sequence stars, as well as seeing how the mean density of stars differs for stars on different parts of the H-R diagram. We then introduce the Ideal Gas Law, which relates pressure, density, and temperature, and show how the internal structure of a star is determined by a continuous tug-of-war between internal pressure trying to blow the star apart, and self-gravity trying to make it collapse. The balance between the two is the state of Hydrostatic Equilibrium. How the balance is maintained, and what happens when it is tipped in favor of either will determine the appearance and subsequent evolution of the star. Recorded 2006 January 18 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1137612537 Wed, 18 Jan 2006 14:28:57 EST astronomy, stars, internal structure, ideal gas law, hydrostatic equilibrium Richard Pogge How long can the Sun continue to shine, and what source of energy does it tap to keep shining? This lecture answers this question by introducing two important energy sources for stars: Gravitational Contraction otherwise known as the Kelvin-Helmholz Mechanism, and Nuclear Fusion. We will show that fusion of 4 Hydrogen nuclei into a Helium nucleus via the proton-proton chain liberates enough energy to provide for the Sun's Luminosity needs for about 10 Billion Years. Recorded 2006 January 19 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Note: the recording mistakenly says January 18th. Oops. Ast162_Wi06_1137689304 Thu, 19 Jan 2006 11:48:24 EST astronomy, stars, sun, hydrogen fusion, kelvin-helmholz mechanism, sunlight Richard Pogge How do stars generate energy in their cores, and once made, how is that energy transported to the surface where it can be radiated away as Luminosity? This lecture revisits nuclear fusion and the Kelvin-Helmholz Mechanism, and discusses the 3 ways energy can be transported in stars: Radiation, Convection, and Conduction. This will lead us to the concept of Thermal Equilibrium in stars, which is the last main piece of stellar physics we need before we can address the question of how stars are formed and evolve in the rest of this Unit. Recorded 2006 January 23 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138030540 Mon, 23 Jan 2006 10:35:40 EST astronomy stars, energy generation, energy transport, fusion, proton-proton chain, CNO cycle, thermal equilibrium, radiation, convection, conduction Richard Pogge How do stars form? The Sun is old and in Hydrostatic and Thermal equilibrium. How did it get that way? This lecture presents the basic steps of star formation as a progress from cold interstellar Giant Molecular Clouds to Protostars in Hydrostatic Equilibrium, and then Pre-Main Sequence evolution which ends in ignition of core Hydrogen fusion and establishing Thermal Equilibrium on the Zero-Age Main Sequence. Recorded 2006 January 24 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138119117 Tue, 24 Jan 2006 11:11:57 EST astronomy, stars, star birth, protostars, zero-age main sequence, stellar evolution Richard Pogge What are the properties of stars on the Main Sequence? This lecture discusses what happens to a star after it alights onto the Main Sequence, burning H to He in its core, and maintaining a state of Hydrostatic and Thermal Equilibrium. We will see how the mass of a star determines its location along the Main Sequence and influences its energy generation and internal structure. We finally introduce the nuclear timescale and derive the Main-Sequence Lifetime for stars, and discuss its consequences. Recorded 2006 January 25 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138228575 Wed, 25 Jan 2006 17:36:15 EST astronomy, stars, main sequence, stellar evolution, nuclear timescale Richard Pogge What happens to a low-mass star (less than 4 solar masses) when it runs out of core Hydrogen and must leave the Main Sequence. This lecture describes the changes inside a low-mass star after Hydrogen exhaustion through the Red Giant, Horizontal Branch, Asymtotic Giant, and Planetary Nebula phases. In the end, we will see the star's envelope and core go their separate ways, the envelope gently puffed off into space, briefly flowering as a Planetary Nebula, and the Carbon-Oxygen core collapsing into a White Dwarf. Recorded 2006 January 26 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138289886 Thu, 26 Jan 2006 10:38:06 EST astronomy, stars, low-mass stars, stellar evolution, red giants, horizontal branch, AGB stars, white dwarfs, planetary nebulae Richard Pogge What happens when a high-mass (more than 4 solar masses) Main Sequence stars runs out of Hydrogen in its core. At first the internal evolution looks like that of a low-mass star, but now we get first a Red Supergiant then a sucession of blue and red supergiant phases as different nuclear fuels are tapped by the star for its energy. This lecture describes the evolution of high-mass stars from the Main Sequence until their eventual ends. Recorded 2006 January 27 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138378239 Fri, 27 Jan 2006 11:10:39 EST astronomy, stars, high-mass stars, stellar evolution, red supergiants, blue supergiants Richard Pogge Once a massive star builds a massive Iron/Nickel core at the end of the Silicon Burning day, it is doomed. A catastrophic core collapse is followed by explosive ejection of the envelope in a Supernova. This lecture describes the stages of a core-bounce supernova explosion, and the subsequent seeding of the interstellar medium with heavy metals by the explosion debris. The fate of the collapsing core is the subject of the next lecture in this series. Recorded 2006 January 30 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138635100 Mon, 30 Jan 2006 10:31:40 EST astronomy, stars, massive-stars, supernovae, supernova remnants, crab nebula, nucleosynthesis, stellar evolution Richard Pogge What happens to the cores left behind at the end of a star's life? This lecture introduces these stellar remnants: White Dwarfs (remnants of low-mass stars held up by Electron Degeneracy Pressure), and Neutron Stars (remnant cores of core-bounce supernovae held up by Neutron Degeneracy Pressure). We also the Chandrasekhar Mass for White Dwarfs, Type Ia Supernovae resulting from a white dwarf getting tipped over the Chandrasekhar Mass, Pulsars (rapidly rotating magnetized neutrons stars), and ask what happens when a neutron star gets tipped over its mass limit. Recorded 2006 January 31 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138726995 Tue, 31 Jan 2006 12:03:15 EST astronomy, stars, white dwarfs, neutron stars, chandrasekhar mass, pulsars, stellar evolution Richard Pogge What happens if even Neutron Degeneracy pressure is insufficient to halt the collapse of gravity? In that case, the object simply collapses in upon itself, approaching a state of infinite density. Such an object has such strong gravity that nothing, not even light can escape from it. We call these Black Holes. This lecture describes the basic properties of black holes, takes an imaginary journey through the event horizon, and discusses observational evidence that stellar-mass black holes (the remnants of the evolution of very massive stars) actually exist, and ends with the suggestion that if Steven Hawking and others are right, black holes may not be so black after all. One Erratum: during the lecture while commenting on the fate of Karl Schwarzschild, for whom the Schwarzschild Radius is named, I incorrectly identify Henry Moseley (killed by a sniper during the Galipoli Campaign of WWI) as one of the discoverers of the neutron. Moseley was the person who discovered that "atomic number" corresponded to nuclear charge, and hence the number of protons in the nucleus. The discoverer of the neutron was James Chadwick, who died in 1974. Recorded 2006 February 1 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138814237 Wed, 01 Feb 2006 12:17:17 EST astronomy, stars, black holes, stellar evolution, gravitational collapse Richard Pogge What are our observational tests of Stellar Evolution? This lecture discusses how we use Hertzsprung-Russell Diagrams of star clusters to test stellar evolution theory, and some of the conclusions we have drawn. In particular, we will see how the age of a star cluster can be estimated from the Main-Sequence Turn-Off for the cluster. We also introduce Open and Globular Clusters, and show how we apply stellar evolution theory to their H-R diagrams. Recorded 2006 February 2 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1138894688 Thu, 02 Feb 2006 10:38:08 EST astronomy, stars, stellar evolution, Herzsprung-Russell Diagrams, open clusters, globular clusters, main sequence Richard Pogge How do we measure distances to astronomical objects that are too far away to use Trigonometric Parallaxes? This first lecture of Unit 4 reviews geometric methods like trigonometric parallaxes, and then introduces the idea of Standard Candles, and how they are used to develop methods for deriving Luminosity Distances based on the Inverse Square Law of Brightness. We will explore three luminosity-based distance methods useful for studying our Galaxy and nearby galaxies: Spectroscopic Parallaxes, Cepheid Variable Period-Luminosity Relation, and the RR Lyrae P-L Relation. Recorded 2006 February 6 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139239861 Mon, 06 Feb 2006 10:31:01 EST astronomy, distances, parallaxes, cepheid variables, rr lyrae variables, cosmology Richard Pogge What is the Milky Way, and what is our place within it? This lecture introduces the Milky Way, the bright band of light that crosses the sky, and describes how we came to our present understanding of the size and shape of the Milky Way Galaxy, and our location in it. Recorded 2006 February 7 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139326589 Tue, 07 Feb 2006 10:36:29 EST astronomy, galaxies, milky way, history of astronomy Richard Pogge How did we come to understand that the Milky Way was just one of billions of other galaxies in a vast Universe? This lecture reviews the history of how we came to recognize that the spiral nebulae were, in fact, other milky ways like our own: vast systems of 100s of billions of stars located millions of parsecs away. The key to understanding their nature was finding the distances to the spiral nebulae compared to the size of our Galaxy. Recorded 2006 February 8 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139413278 Wed, 08 Feb 2006 10:41:18 EST astronomy, galaxies, milky way, andromeda, history of astronomy Richard Pogge Andromeda is the nearest bright spiral galaxy to the Milky Way, and a near twin in terms of stellar and gas content. This lecture discusses the idea of stellar populations and chemical evolution in galaxies as determined by combining observations from within (the Milky Way) and without (Andromeda). At the end, two other features of these galaxies, their supermassive central black holes, is introduced, setting up a question to be addressed in later lectures. Recorded 2006 February 9 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139501089 Thu, 09 Feb 2006 11:04:49 EST astronomy, galaxies, milky way, andromeda, stellar populations, chemical evolution Richard Pogge What are Spiral Galaxies? This lecture describes the basic properties of spiral galaxies, their patterns of rotation and how that lets us measure their masses, and the nature of the spiral arms as waves moving through the disk and triggering formation of new stars. Recorded 2006 February 10 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139592821 Fri, 10 Feb 2006 12:33:41 EST astronomy, galaxies, spiral galaxies, star formation Richard Pogge What are the different types of galaxies? What hints can they give us as to the structure and evolution of galaxies? This lecture introduces the Hubble Classification System for galaxies, and describes the properties of each major class. This detailed overview gives us some tantalizing clues as to the formation and evolution of galaxies that will be picked up in subsequent lectures. Recorded 2006 February 13 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139845097 Mon, 13 Feb 2006 10:38:17 EST astronomy, galaxies, spiral galaxies, elliptical galaxies, irregular galaxies, dwarf galaxies, stellar and gas content Richard Pogge Galaxies are found in groups and clusters, and these are only the start of a hierarchy of cosmic structures up to the largest scales observed. This lecture introduces the properties of groups and clusters of galaxies, superclusters (clusters of clusters), and large scale structure with filaments of superclusters surrouning vast voids. We start with our Local Group, and then expand our view to encompass the depths of intergalactic space. Recorded 2006 February 14 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1139935355 Tue, 14 Feb 2006 11:42:35 EST astronomy, galaxes, groups, clusters, superclusters, filaments, voids, large-scale structure Richard Pogge What happens if two galaxies collide? The average distance between bright galaxies is only about 20 times their size, so over the history of the Universe (14 Billion years), we expect that most bright galaxies will have had at least one close gravitational encounter with a neighboring galaxy. This lecture explores what happens when two galaxies undergo interactions ranging from passing tidal interactions to head-on collisions, all the way to multiple collisions and galaxy "cannibalism" in the centers of large clusters. While at first glance galaxy interactions explain rare "peculiar" galaxies, on closer examination we find that galaxy interactions and mergers are central to understanding the assembly and evolution of galaxies. At the end, we take a speculative look at the distant future 3-4 Billions years hence if in fact Andromeda and the Milky Way are on a collision course. Recorded 2006 February 15 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140022975 Wed, 15 Feb 2006 12:02:55 EST astronomy, galaxies, tidal interactions, starbursts, galaxy collisions Richard Pogge What are Active Galaxies and Quasars? We have good reason to think that buried deep in the hearts of nearly every (?) bright galaxy is a supermassive black hole with masses of millions or even billions of times the mass of the Sun. Most, like the one in our Milky Way, are quiescent, but in about 1% of galaxies, they are fed enough matter (up to about a sun's worth per year), and light up as an Active Galactic Nucleus (AGN) that can outshine an entire galaxy full of billions of stars. This lecture reviews the observed properties of Active Galaxies, the riddle of the Quasars, and the recognition that they are powered by the accretion of matter onto supermassive black holes. The lecture ends with some open questions in this active area of current research. Recorded 2006 February 16 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140104154 Thu, 16 Feb 2006 10:35:54 EST astronomy, galaxies, supermassive black holes, active galaxies, quasars, radio galaxies Richard Pogge What are space and time? To begin our exploration of the evolving Universe, we must first understand what we mean by space and time. This lecture contrasts the Newtonian view of the World, with its absolute space and absolute time, with that of Einstein, who showed that space and time were not absolute but relative constructs, and that only spacetime, unified by light, was independent of the observer. This requires such non-intuitive notions as the speed of light being the same for all observers regardless of their motion, and that observers moving relative to each other will agree on the same physical laws and speed of light, but disagree on lengths, times, masses, etc. measured by applying those laws. This sets the stage for Einstein's revision of the Law of Gravity, General Relativity, which we will review in the following lecture. Recorded 2006 February 20 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140449526 Mon, 20 Feb 2006 10:32:06 EST astronomy, special relativity, spacetime Richard Pogge What is gravity? Newton left that question unanswered when he formulated his inverse square law of the gravitational force, framing no hypothesis for what agency transmits gravity, only asserting it was an action at a distance. Einstein brought gravity into relativity by answering Newton's unanswered question with his General Relativity, our modern theory of gravity. In Einstein's formulation, Matter tells spacetime how to curve, and curved spacetime tells matter how to move. This lecture presents the basic picture of General Relativity, and introduces some of its observational consequences. The surprising conclusion is that instead of space and time being a backdrop for physics in Newton's view, united into spacetime by Relativity they are understood to be physical and dynamic. This is important for understanding how the Universe as a whole works. Recorded 2006 February 21 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140535917 Tue, 21 Feb 2006 10:31:57 EST astronomy, general relativity, gravity Richard Pogge What are the implications of Relativity for the Universe? This lecture introduces the Cosmological Principle, which states that the Universe is Homogeneous and Isotropic on Large Scales. Applying this to his then-new General Relativyt, Einstein got a surprise: the Universe must either expand or contract in response to all the matter/energy that fills it, something not observed in 1917. To attempt to stabilize the Universe, he introduced a Cosmological Constant (Lambda), that was to prove his greatest blunder. Subsequent theoretical and observational work was to establish that the Universe is indeed expanding systematically, if you look on scales large enough (the scale of galaxies). We will review observational evidence for the large-scale Homogeneity and Isotropy of the Universe, Einstein's brilliant conjecture, and see how the Cosmological Constant maybe wasn't such a blunder after all, as it has recently made a comeback of sorts. We'll explore these themes in greater detail in subsequent lectures. Recorded 2006 February 22 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140623006 Wed, 22 Feb 2006 10:43:26 EST astronomy, cosmology, einstein, expansion of the Universe Richard Pogge How did we discover that the Universe is Expanding? What does it mean that it is expanding? This lecture introduces Hubble's Law, the observational evidence that the Universe is systematically expanding. As galaxies get more distant from us, the apparent speed of recession gets larger in proportion. The proportionality is the rate of expansion, called the Hubble Parameter (H0). This leads us to the idea of expanding space, and the Cosmological Redshift, which combined with the Hubble Law allows us a way to estimate very large cosmic distances. We will take up the more thorny issue of the Cosmic Distance Scale in tomorrow's lecture. Recorded 2006 February 23 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140709056 Thu, 23 Feb 2006 10:37:36 EST astronomy, cosmology, expanding universe, Hubble Parameter, redshift Richard Pogge How do we measure distances on cosmic scales? This lecture describes the rungs in the cosmic distance ladder from measuring the AU in our own Solar System out into the Hubble expansion of the universe. These distances form the basis of the measurements that let us piece together the present, past, and future history of the expanding Universe, setting the stage for next week's lectures. Recorded 2006 February 24 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1140795158 Fri, 24 Feb 2006 10:32:38 EST astronomy, cosmology, cosmic distances Richard Pogge The Universe today is old, cold, low-density, and expanding. If we run the expansion backwards, we will eventually find a Universe where all the matter was in one place where the density and temperature are nearly infinite. We call this hot, dense initial state of the Universe the Big Bang. This lecture introduces the Big Bang model of the expanding universe, and how the history of the Universe depends on two numbers: the curretn expansion rate (H0), and the relative density of matter and energy (Omega0). Combined with observations, these give us an estimate of the age of the Universe of 14.0 +/- 1.4 Gyr. Recorded 2006 February 27 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141066739 Mon, 27 Feb 2006 13:58:59 EST astronomy, universe, cosmology, big bang, age of the Universe, origin of the Universe Richard Pogge Is there any evidence that the Universe was very hot and dense in the distant past as predicted by the Big Bang model of the expanding Universe? This lecture examines observational tests of the Big Bang Model. We have already covered expansion in the previous lecture. Today we look at Primordial Nucleosynthesis, the creation of light elements from fusion during the first 3-4 minutes of the hot phases of the Big Bang, and the Cosmic Background Radiation, the relic blackbody radiation remaining from when the Universe became transparent to light 300,000 years after the Big Bang. Both predictions of the Big Bang Model have been spectacularly confirmed by observations of the present-day Universe. These give us confidence that the Big Bang, in broad outline, is the correct physical model of our expanding Universe. Recorded 2006 February 28 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141141260 Tue, 28 Feb 2006 10:41:00 EST astronomy, cosmology, universe, big bang, cosmic background radiation, primordial nucleosynthesis, origin of Helium Richard Pogge What was the Universe like from the earliest phases immediately after the Big Bang to the present day? This lecture reviews the physics of matter, and follows the evolution of the expanding Universe from the first instants after the Big Bang, when all 4 forces of nature were unified in a single grand-unified superforce until the emergence of the visible Universe we see around us today. Recorded 2006 March 1 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141230222 Wed, 01 Mar 2006 11:23:42 EST astronomy, cosmology, big bang, early universe Richard Pogge What is the ultimate fate of the Universe? The ultimate fate of the Big Bang is either expansion to a maximum size followed by re-collapse (the Big Crunch) or eternal expansion into a cold, dark, disordered state (the Big Chill). Which of these is our future depends on the current density of matter and energy in the Universe, Omega0. This lecture examines our current knowledge of the matter and energy content of the Universe, which leads to the surprising discovery that we live in a Universe that is Flat (Omega0=1), Infinite, and Accelerating! We will end the lecture by exploring the possible fate of an infinite accelerating Universe. Recorded 2006 March 2 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141313547 Thu, 02 Mar 2006 10:32:27 EST astronomy, cosmology, big bang, big chill, big crunch, ultimate fate of the Universe Richard Pogge How will the Sun evolve? The Sun is now a middle-aged, low-mass, Main Sequence star in a state of hydrostatic and thermal equilibrium that has consumed about half of the Hydrogen available for fusion in its core. What will its subsequent evolution be as its core runs out of Hydrogen? This lecture describes our current state of understanding of the expected evolution of the Sun, informed by a combination of state-of-the-art solar models and stellar evolution codes, and data gathered from observations of nearby stars in our Galaxy. We will trace the future history of the Sun from the present until it begins its final phase as a fading White Dwarf some 8 Billion years in the future. Along the way, we'll also ask what will become of Earth. Recorded 2006 March 6 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141659078 Mon, 06 Mar 2006 10:31:18 EST astronomy Richard Pogge We are not made of the same matter as most of the Universe! This surprising conclusion, that the ordinary matter we are made of (protons, neutrons, and electrons) constitute only 13% or so of the total matter in the Universe, the rest being in the form of Dark Matter. Further, this dark matter is only about 30% of the combined matter and energy density of the Universe, the remaining 70% of which appears to be a form of Dark Energy that fills the vacuum of space and acts in the present day to accelerate the expansion of the Universe. This lecture will summarize the state of our understanding of Dark Matter and Dark Energy, and look at the questions remaining to be answered in this active area of current research. Recorded 2006 March 7 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141749746 Tue, 07 Mar 2006 11:42:26 EST astronomy, cosmology, dark matter, dark energy, microlensing, galaxies, galaxy clusters Richard Pogge Can we travel through time? This is not a frivilous, science-fiction kind of question. Certain restricted kinds of time travel are in fact allowed by classical General Relativity. This lectures takes up this question, and looks at some of the surprising answers that have been found. Recorded 2006 March 8 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141835994 Wed, 08 Mar 2006 11:39:54 EST astronomy, relativity, general relativity, time travel, black holes, twin paradox, grandfather paradox Richard Pogge Are we alone in the Universe? This is the first part of a 2-part lecture that will explore the question of life and the Universe. We will look at the conditions needed for life, and address the question of how often we expect those conditions to be satisfied in our own Galaxy. In this part, we introduce the Drake Equation and make some basic estimates. To be honest, it was supposed to be one lecture, but I ran over time and ran into the bell. Oops! Very embarrasing. Tomorrow's lecture will finish up our discussion of life in the Universe, and then wrap up Astronomy 162 for the quarter. Recorded 2006 March 9 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1141918975 Thu, 09 Mar 2006 10:42:55 EST astronomy, life, planets, drake equation, extraterrestrials, conditions for life Richard Pogge How can we search for extraterrestrial intelligence, and what are we looking for? This second part of a 2-part lecture picks up where we left off yesterday by examining SETI, the Search for ExtraTerrestrial Intelligence, and reviews what we might look for and how. We will use this as a point of departure to then briefly review where we have come and what we have learned in Astronomy 162, bringing this course to a close for Winter Quarter 2006. Recorded 2006 Mar 10 in 1008 Evans Laboratory on the Columbus campus of The Ohio State University. Ast162_Wi06_1142004914 Fri, 10 Mar 2006 10:35:14 EST astronomy, SETI, life, the universe Richard Pogge A new podcast, Astronomy 141, Life in the Universe, is available for those interested in continuing an exploration of topics in modern astronomy. Ast162_Wi06_1260137150 Sun, 06 Dec 2009 17:05:50 EST astronomy