The most played episodes among Podcast App listeners.

1. 1
   Number 1: 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 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.

   January 24, 2006·0min
   Play
2. 2
   Number 2: 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. 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.

   January 18, 2006·0min
   Play
3. 3
   Number 3: 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. 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.

   January 25, 2006·0min
   Play
4. 4
   Number 4: 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 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.

   January 23, 2006·0min
   Play
5. 5
   Number 5: 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. 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.

   January 19, 2006·0min
   Play