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Pulsars and Neutron Stars
Reading: FETU chapter 29 sections 1-4. Chapter 30 sections for next week. |
Concept I: "Quantum Pressure" in
neutron stars.
Concept II: The chandra limit in neutron stars Concept III: The light-house effect. Just learned in tutorial #5 & Monday's class: "Quantum Pressure" in white dwarfs & the Chandrasekar limit for white dwarfs (~1.5 solar mass). What happens to cores of stars that are MORE MASSIVE THAN THAT? We learned before spring break: Super nova. Protons --> Neutrons + Neutrinos + anti-electrons. So core becomes mostly neutrons. Pauli exclusion principle for neutrons: Neutrons don't "want" to be too close to each other. Radius of neutron stars of 1.5 solar mass - roughly the distance from Lewisburg to I-80. (1000 times smaller than WD's). Quantum pressure holds against gravity for cores of up to ~ 2 solar mass. That's the Chandrasekar limit for neutron stars. What's beyond that? Probably black holes (next week). Are there any neutron stars?
Pulsar discovery:
Dubbed LGM. Many more found, unrelated. Now associated with Neutron stars. Why? 1. Incredibly accurate intervals - probably rotations. White dwarf (earth size) spins around once in a second - pieces fly off because of inertia. Not white dwarfs. 2. Neutron stars should form in supernovae. The crab nebula is a supernova observed in 1054 AD. We now see a pulsar at the center of this explosions.This pulsar emits regular light too! How do pulsars work? The lighthouse effect: Use two fleshlight, spin.
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