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Announcements

Announcements. Exam 2 is scheduled for Thursday March 7. Tentatively will cover Chapters 3 – 5 and probably Chapter 6. Sample Questions are posted

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Announcements

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  1. Announcements • Exam 2 is scheduled for Thursday March 7. Tentatively will cover Chapters 3 – 5 and probably Chapter 6. Sample Questions are posted • Project topics are due before spring break (March 7). Decide on a topic and come talk to me about it. The topic can be anything of current cosmological interest.

  2. Type IIa Supernova:Death of a massive star Photodisintegration Fe + g He Reverse Beta Decay e- + p+ n + n

  3. Other Types of Supernovae

  4. Type Ia: White Dwarf Explosion Watch Tycho’s Supernova video and Type Ia SN videos When a white dwarf exceeds the Chandrasekhar limit of 1.2 Msun, it detonates in a Type Ia supernova. The spectrum has no hydrogen lines but lots of silicon and iron. The white dwarf star is completely destroyed.

  5. Type Ib: Stripped Supergiant If a massive star has its outer layers stripped off, perhaps by previous eruptions or a companion, it will be a blue supergiant when it dies. No hydrogen in the spectrum but lots of helium.

  6. Type Ic: Naked Supergiant If even the helium has been stripped off, there will be only heavier elements in the spectrum

  7. What is left after a supernova? A supernova remnant is only visible for a few thousand years before it fades from view.

  8. Pulsars: LGM? Jocelyn Bell and Antony Hewish discovered extremely regular radio pulses coming from an object in Vulpecula

  9. Pulsars are spinning Neutron Stars The Lighthouse Model

  10. The Lighthouse Model

  11. The Crab pulses in all wavelengths

  12. What causes emission in all wavelengths? Synchrotron Radiation

  13. The Heart of the Crab Nebula Intense “winds” blowing away from the equator of the pulsar create a disk of swirling material around the pulsar. Jets can also be seen emanating from the poles of the pulsar. Watch Crab Pulsar Winds video

  14. If a pulsar is radiating energy, where is it coming from?

  15. Pulsar Spin-down and Glitches Normal neutron stars can also show sudden changes in their rotational periods An SGR is a Soft Gamma ray Repeater. They have magnetic fields thousand of times more intense than normal neutron stars.

  16. Internal Structure of a Neutron Star At the very center may be a core of strange matter: matter composed of a “fluid” of strange quarks

  17. When a glitch occurs on a magnetar, a blast of gamma rays is emitted Watch Magnetar Flare videos posted in the content section of the class D2L shell

  18. Pulsars in binary systems can be extremely active

  19. Millisecond Pulsars Watch Millisecond Pulsar video

  20. Even More Bizarre: Binary Pulsars Watch Binary Pulsar, Formation of Binary Pulsar and Colliding Neutron Stars video

  21. Is there a limit to mass of a neutron star? ~2 – 3 Msun

  22. Hypernova What if the iron core is more than 3 solar masses?

  23. Black Holes and relativity Newtonian physics won’t work here. We need new physics

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