Quasars and Accretion Disk Model
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Questions and Answers

What could lead to a quasar having an arbitrarily high luminosity?

  • The gravitational pull of the central mass
  • A small supply of matter close to the black hole
  • Radiation pressure from the inner part of the accretion disk
  • A large supply of matter available sufficiently close to the black hole (correct)

    • What is the effect of radiation pressure on the accreting material in the accretion disk?

  • It directs the material inwards towards the central mass
  • It directs the material outwards, in opposition to the gravitational pull of the central mass (correct)
  • It increases the gravitational pull of the central mass
  • It decreases the accretion rate

    • What is the Eddington limit related to?

  • The black hole's mass
  • The accretion disk's temperature
  • The gravitational pull of the central mass
  • The maximum quasar luminosity for a fixed black hole mass (correct)

    • What would be the state of the hydrogen in the accretion flow at some stage?

    <p>Become ionized due to high-frequency radiation</p> Signup and view all the answers

    What is the composition of the accretion flow after the hydrogen becomes ionized?

    <p>A mixture of unbound electrons and unbound protons in a plasma</p> Signup and view all the answers

    Why is hydrogen considered the obvious candidate in the accretion flow?

    <p>It is the most abundant element in the Universe</p> Signup and view all the answers

    What is the main reason why the electrons are not 'blown' away despite the strong radiation force on them?

    <p>A strong local electromagnetic restoring force prevents the separation of electrons and protons</p> Signup and view all the answers

    Why is the gravitational force on the proton much stronger than that on the electron?

    <p>Because the proton is much more massive than the electron</p> Signup and view all the answers

    What is the direction of the momentum of a photon moving radially outwards from a quasar?

    <p>Outwards away from the quasar</p> Signup and view all the answers

    What is the main factor that determines the strength of the radiation force on an electron?

    <p>The charge of the electron</p> Signup and view all the answers

    What is the net result of the competing forces of gravity and radiation pressure on a hydrogen atom?

    <p>The balance between the two forces determines the motion of the hydrogen atom</p> Signup and view all the answers

    What is the reason why the radiation force on the electron is much greater than that on the proton?

    <p>The Thomson cross-section scales inversely with the square of the particle's mass</p> Signup and view all the answers

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