Astronomy 162 - Stars, Galaxies, & The Universe

  • Autor: Vários
  • Narrador: Vários
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Sinopse

Astronomy 162, Stars, Galaxies, and the Universe, is part 2 of a2-quarter introductory Astronomy for non-science majors taught at TheOhio State University. This podcast presents lecture audio fromProfessor Richard Pogge's Winter Quarter 2006 class. All of thelectures were recorded live in 1008 Evans Laboratory on the OSU MainCampus in Columbus, Ohio.

Episódios

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

    13/02/2006

    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.

  • Lecture 26: Spiral Galaxies

    10/02/2006

    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.

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

    09/02/2006

    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.

  • Lecture 24: The Realm of the Nebulae

    08/02/2006

    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.

  • Lecture 23: The Milky Way

    07/02/2006

    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.

  • Lecture 22: The Cosmic Distance Problem

    06/02/2006

    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.

  • Lecture 21: Testing Stellar Evolution

    02/02/2006

    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.

  • Lecture 20: Black Holes

    01/02/2006

    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

  • Lecture 19: Extreme Stars: White Dwarfs & Neutron Stars

    31/01/2006

    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.

  • Lecture 18: Supernovae

    30/01/2006

    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.

  • Lecture 17: The Evolution of High-Mass Stars

    27/01/2006

    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.

  • Lecture 16: The Evolution of Low-Mass Stars

    26/01/2006

    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.

  • Lecture 15: The Main Sequence

    25/01/2006

    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.

  • Lecture 14: Star Formation

    24/01/2006

    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.

  • Lecture 13: Energy Generation and Transport in Stars

    23/01/2006

    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.

  • Lecture 12: As Long as the Sun Shines

    19/01/2006

    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.

  • Lecture 11: The Internal Structure of Stars

    18/01/2006

    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.

  • Lecture 10: Synthesis: The Herzsprung-Russell Diagram

    17/01/2006

    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.

  • Lecture 09: Stellar Spectra

    13/01/2006

    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.

  • Lecture 08: Stellar Masses & Radii

    12/01/2006

    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.

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