| Today: Review HW if necessary | |
| End Ch. 11: Neutron Stars, Black Holes | |
| Review topics if time |
| Nothing can stop collapse after neutron pressure fails | ||
| Escape velocity from a surface at radius R: | ||
| As R shrinks (but M is fixed), Vescape gets larger and larger | ||
| At some point VEscape= c (speed of light) | ||
| Happens at Schwarzschild radius: | ||
| Not even light can escape from within this radius | ||
| The Schwarzschild Radius: | |||
| Mass in solar masses Rs (km) | |||
| 10 | |||
| 3 | |||
| 2 | |||
| 1 | |||
| 0.000003 (Earth) | |||
| The Schwarzschild Radius: | |||
| Mass in solar masses Rs (km) | |||
| 10 30 | |||
| 3 9 | |||
| 2 6 | |||
| 1 3 | |||
| 0.000003 (Earth) 0.9 cm | |||
| Remember – gravity is same as before, away from mass | ||
| Black holes do NOT necessarily pull all nearby material in | ||
| A planet orbiting a new black hole would just keep on orbiting as before (assuming the ejected material or radiated energy didn’t have an effect) | ||
| Any mass can potentially be made into a black hole – if you can compress it to a size smaller than RS = 2GM/c2 | ||
| 1 MSun: 3.0 km 106 MSun 3´106 km 1 MEarth 8.9 mm | ||
| If you do make material fall into a black hole, material will be falling at close to the speed of light when it reaches RS | ||
| If that falling gas collides with and heats other gas before it reaches RS, then light from that hot material (outside RS) can escape (important in quasars!). | ||
| By definition – can’t see light from black hole itself | ||
| Can see large amounts of energy released by falling material just before it crosses RS | ||
| Can see motion of nearby objects caused by gravity of black hole | ||
| Example: Like White Dwarf accretion disk but w/ black hole instead | |||
| Gas from red giant companion spills over towards black hole | |||
| Gas spirals in toward black hole, through accretion disk | |||
| Gas will be much hotter because it falls further, to very small RS | |||
| Gas will be moving at very high velocity | |||
| Much faster than with white dwarf since much closer (P2 µ a3) | |||
| Signature of black hole: Very high energy release, very high velocity | |||
| We find MASSIVE black holes in centers of most galaxies | |||
More Cool Stuff About Black Holes
| Time Dilation – originally “Frozen Stars” | |
| Gravitational Redshift | |
| Wicked Tidal Forces | |
| Hawking Radiation |
| Chapter 5: Just a few topics | |||
| Telescope resolution | |||
| Function of size, wavelength | |||
| Observations at different wavelengths | |||
| Chapter 6: Starlight and Atoms | |||
| Model Atom, parts, energy levels | |||
| Emission and Absorption Lines | |||
| Blackbody Radiation | |||
| Wien’s Law, Steffan-Boltzmann Law | |||
| Spectra of Stars | |||
| Balmer thermometer, spectral types (OBAFGKM) | |||
| Doppler Effect | |||
| Chapter 7: The Sun | |||
| Atmospheric Structure | |||
| Temperature, density, etc., with radius | |||
| Sunspots/Magnetic Phenomena | |||
| What are they? Why do they exist? | |||
| Nuclear Fusion – proton-proton chain | |||
| What is it? How does it produce energy? | |||
| Solar Neutrino “Problem” | |||
| What is it? Is it still a problem? | |||
| Chapter 7: The Sun – example question | |
| Q. The fusion process in the sun, the "proton-proton" chain, requires high temperatures because: | |
| c of the ground-state energy of the Hydrogen atom. | |
| c of the presence of Helium atoms. | |
| c the colliding protons need high energy to overcome the Coulomb barrier. | |
| c of the need for low density. | |
| c the neutrinos carry more energy away than the reaction produces. |
| Chapter 8: The Properties of Stars | |||
| Distances to Stars | |||
| Parallax and Parsecs | |||
| Spectroscopic Parallax | |||
| Intrinsic Brightness: Luminosity | |||
| Absolute Magnitude | |||
| Luminosity, Radius, and Temperature | |||
| Hertzsprung-Russell (H-R) Diagram | |||
| Luminosity Classes (e.g., Main Sequence, giant) | |||
| Masses of Stars | |||
| Binary Stars and Kepler’s Law | |||
| Mass-Luminosity Relationship | |||
| Chapter 8: Properties of Stars—example question | ||
| Q. A star’s luminosity depends only on the star’s: | ||
| c distance and diameter. | ||
| c temperature and distance. | ||
| c distance. | ||
| c temperature and diameter. | ||
| c apparent magnitude | ||
| Another version of the question can be made for apparent magnitude . | ||
| Ch. 9: The Formation & Structure of Stars | |||
| Interstellar Medium | |||
| Types of Nebulae (emission, reflection, dark) | |||
| Interstellar Reddening from dust | |||
| Star formation | |||
| Protostar Evolution on H-R Diagram | |||
| Fusion (CNO cycle, etc.) | |||
| Pressure-Temperature “Thermostat” | |||
| Stellar Structure (hydrostatic equilibrium, etc.) | |||
| Convection, radiation, and opacity | |||
| Stellar Lifetimes | |||
| Ch. 10: The Deaths of Stars | ||
| Evolution off the main sequence (=> giant) | ||
| Star Cluster Evolution on H-R Diagram | ||
| Degenerate Matter | ||
| Planetary Nebulae and White Dwarfs | ||
| Binary Star Evolution (Disks, Novae, etc.) | ||
| Massive Star Evolution and Supernovae | ||
| Ch. 10: The Deaths of Stars—example question | ||
| Q. Massive stars cannot generate energy through iron fusion because: | ||
| c iron fusion requires very high densities. | ||
| c stars contain very little iron. | ||
| c no star can get high enough for iron fusion. | ||
| c iron is the most tightly bound of all nuclei. | ||
| c massive stars go supernova before they create an iron core. | ||
Chapter 11: Neutron Stars & Black Holes
| Neutron Stars | |||
| Pulsars (Radio pulsation, lighthouse model) | |||
| Properties (size, density, composition) | |||
| Black holes | |||
| Schwarzschild Radius | |||
| Properties | |||
| Detection (Gravity, X-rays from Disks) | |||