Astronomy 162 - Stars, Galaxies, & the Universe

Astronomy 162 - Stars, Galaxies, & the Universe episodes:

• 12.06.2009

  Astronomy 141 Podcast Teaser

  A new podcast, Astronomy 141, Life in the Universe, is available for those interested in continuing an exploration of topics in modern astronomy.

  
• 11.27.2006

  Lectures 1-4: An Explanation

  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.

  
• 03.10.2006

  Welcome to Astronomy 162

  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.

  
• 03.10.2006

  Lecture 44: Life, the Universe, and Everything (Life Part II)

  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...

  
• 03.09.2006

  Lecture 43: Life in the Universe, Part I

  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...

  
• 03.08.2006

  Lecture 42: Time Travel

  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...

  
• 03.07.2006

  Lecture 41: Dark Matter & Dark Energy

  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...

  
• 03.06.2006

  Lecture 40: The Once and Future Sun

  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...

  
• 03.02.2006

  Lecture 39: The Fate of the Universe

  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...

  
• 03.01.2006

  Lecture 38: The First Three Minutes

  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...

  
• 02.28.2006

  Lecture 37: The Whispers of Creation

  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...

  
• 02.27.2006

  Lecture 36: The Big Bang

  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,...

  
• 02.24.2006

  Lecture 35: The Cosmic Distance Scale

  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...

  
• 02.23.2006

  Lecture 34: The Expanding Universe

  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...

  
• 02.22.2006

  Lecture 33: Einstein's Universe

  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...

  
• 02.21.2006

  Lecture 32: Space, Time, & Gravity: General Relativity

  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...

  
• 02.20.2006

  Lecture 31: A Tale of Two World Views: Special Relativity

  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...

  
• 02.16.2006

  Lecture 30: Active Galaxies & Quasars

  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...

  
• 02.15.2006

  Lecture 29: When Galaxies Collide

  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...

  
• 02.14.2006

  Lecture 28: Groups & Clusters of Galaxies

  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...

  
• 02.13.2006

  Lecture 27: Spirals, Ellipticals, & Irregular (Oh My!)

  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...

  
• 02.10.2006

  Lecture 26: Spiral Galaxies

  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...

  
• 02.09.2006

  Lecture 25: A Tale of Two Galaxies, The Milky Way and Andromeda

  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...

  
• 02.08.2006

  Lecture 24: The Realm of the Nebulae

  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...

  
• 02.07.2006

  Lecture 23: The Milky Way

  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...

  
• 02.06.2006

  Lecture 22: The Cosmic Distance Problem

  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...

  
• 02.02.2006

  Lecture 21: Testing Stellar Evolution

  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...

  
• 02.01.2006

  Lecture 20: Black Holes

  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...

  
• 01.31.2006

  Lecture 19: Extreme Stars: White Dwarfs & Neutron Stars

  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...

  
• 01.30.2006

  Lecture 18: Supernovae

  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...

  
• 01.27.2006

  Lecture 17: The Evolution of High-Mass Stars

  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...

  
• 01.26.2006

  Lecture 16: The Evolution of Low-Mass Stars

  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,...

  
• 01.25.2006

  Lecture 15: The Main Sequence

  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. ...

  
• 01.24.2006

  Lecture 14: Star Formation

  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...

  
• 01.23.2006

  Lecture 13: Energy Generation and Transport in Stars

  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...

  
• 01.19.2006

  Lecture 12: As Long as the Sun Shines

  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....

  
• 01.18.2006

  Lecture 11: The Internal Structure of Stars

  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....

  
• 01.17.2006

  Lecture 10: Synthesis: The Herzsprung-Russell Diagram

  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...

  
• 01.13.2006

  Lecture 09: Stellar Spectra

  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...

  
• 01.12.2006

  Lecture 08: Stellar Masses & Radii

  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...

  
• 01.11.2006

  Lecture 07: Stellar Brightness

  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...

  
• 01.10.2006

  Lecture 06: The Motions of the Stars

  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...

  
• 01.09.2006

  Lecture 05: Distances of the Stars

  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...