Ast 105 1st Edition Lecture 15Outline of Last LectureI. Super GiantsII. Special Relativity a. 2 postulatesb. Postulate consequencesIII. General Relativity IV. Gravitational Red ShiftV. Black Holesa. How Black Holes formb. Details of i. Schwarzschild Outline of Current LectureI. Schwarzschild Radius II. No Hair Theorem III. Roy KerrIV. Falling into a Black Hole a. Victims view pointb. Onlookers view pointV. Hawking Radiation VI. Summary on Worm HolesVII. Galaxies Current LectureSchwarzschild Radius - RSCH=(2GM)/c2- We can use this to find radius of Earth so that it becomes a black hole- Schwarzschild radius is the distance from the singularity to the event horizon - Event horizon= point of no return in a black hole No Hair Theorem - From classical general relativity - Much of the features of the object are radiated away (as gravitational waves)- Only 3 physical macroscopic properties remain o Masso Angular momentum (spin)o Electric charge No-spin black hole: Schwarzschild black hole Spin black hole: (with rotation) Kerr black holeRoy Kerr - 1963- First to understand the physics of a spinning black hole Kerr black hole Falling Into a Black Hole Lowering a guy into a black hole we are in a space ship lowering him in, we observe:1. His motions slow down2. Light from his flash light is red shifted3. His clock is ticking slower and slower 4. Stretching of his lower extremities, etc…5. Motion freezes, and everything fades away Victim’s viewpoint:1. His motions are normal 2. Light from above is blue shifteda. His light is still white to him 3. His clock ticks at a normal pace4. He sees his feet getting stretched, but feels normal5. He sees all of the stars in the universe; he sees the back of his head; he can also see back in time (if curved black hole)Hawking Radiation - Hawking realized that black holes eventually evaporate - This evaporation takes a very long time Black holes w/ mass of 5xMsun take 1062 years to fully evaporate - Evaporation is due to quantum particlesWormhole- 2 ways to graph Space sheet Time sheet- Also run on the time axiso (“time travel”)Galaxies- our solar system is in the Milky Way Galaxy - in our visible universe, there are about 104 galaxies that’s 100 Billion galaxies Milky Way is just one of them - Before 1923, it was thought that there was just one galaxy (ours)Edwin Hubble- 1923- he took photographs of a distant object, M31- examined his photographic plates and noticed that Cepheid’s existed on M31 We recall that Cepheid’s have a period-luminosity
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