Card Set Information

2011-12-07 00:00:13

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  1. How do stars form?
    Out of giant clouds of interstellar gas, molecules, and dust.
  2. What happens as stars collapse out of the giant clouds of gas?
    They form disks of rotating material and jets of outflowing material.
  3. Adiabatic contraction
    gas gets denser, hotter
  4. Why do disks around protostars rotate?
    Because of conservation of angular momentum
  5. Before the sun reaches the main sequence...
    • It contracts along "Hyashi Tracks" in the HR Diagram
    • 50,000 years
  6. How long is the sun on the main sequence?
    10-11 billion years
  7. Why will the sun get hotter an brighter in 1 billion years?
    Greenhouse Effect
  8. What will happen when the H in the Sun's core is used up?
    • It will become a Red Giant
    • H burning shell
    • Outer layers will blow out in a wind
  9. What will happen when the core of the sun becomes hot enough?
    • Triple Alpha reaction
    • Fuses He to C
  10. Eventually the sun will become a...?
    • Planetary Nebula
    • bright dense white dwarf in the center, outer layers blown and lit by core
  11. What are white dwarfs in?
    Hydrostatic Equilibrium
  12. Whay prevents further gravitational collapse in white dwarfs?
    Electron degeneracy pressure
  13. Stars that are more massive than the sun experience...
    much faster evolution
  14. During the Red Giant phase, massive stars are hot enough to...?
    • produce C, N, and O (CNO cycle)
    • the core of the star is an onion layered set of heavy elements before it explodes
  15. A 20 solar mass star explodes as a...?
    • supernova
    • core collapses into a neutron star or black hole
  16. What is a neutron star?
    neuron degenerate-the neutron degeneracy pressure keeps the star from collapsing
  17. Supernovae
    Very bright, observation of them
  18. Last supernova in Milky Way?
    1604, 1987 in Large Magellanic cloud
  19. Brown Dwarfs
    low mass, gravitational collapse is stopped by electron degeneracy pressure, never hot enough to burn H to He, dim and cold
  20. What a star does after it leaves the main sequence depends on its...?
  21. Astronomer who first outlined the physics of white dwarfs and neutron stars?
  22. All elements heavier than He on Earth...?
    made by stars which died and distributed their mass into the interstellar cloud from which the solar system collapsed
  23. Binary stars that contain a white dward and a second main sequence star which dumps mass can be...?
    nova, cataclysmic variable, Type 1a Supernova
  24. What are pulsars?
    rotating neutron stars which emit pulses of radio emission
  25. Black holes?
    objects where the escape velocity is greater than the speed of light
  26. What is Special Relativity?
    Einstein's theory of physics-objects are travelling with velocities near the speed of light (time dilation, contraction along the direction of the motion)
  27. What is General Relativity?
    Einstein's theory of physics-places where gravity is strong, gravity curves space and times is slowed by gravity, light bent and redshifted
  28. GPS systems are an example of where...?
    special and general relativity must be taken into account
  29. What kind of galaxy is the Milky Way?
    spiral galaxy
  30. What is in the Milky Way?
    200 billion stars, gas, dust, globular clusters, dark matter
  31. Who tried to derive the shape of the Milky Way?
    William and Caroline Herschel
  32. What did they think was the center of the universe?
    The sun
  33. What did Shapley use to find that the Sun is not the center of the Milky Way?
    RR Lyraes in Globular clusters
  34. Some stars and the globular clusters are not in the disk and do what?
    orbit in spherically shaped halos
  35. Where are stars forming today?
    The spiral arms in the disk
  36. The H was mapped with what?
    21cm radiation in the radio, which is produced when electrions flip their spin
  37. What allows ust to map the molecular gas in the Milky Way and why?
    CO, molecule rotates and vibrates
  38. What does the dust consist of?
    • small particles containing silicon, carbon, and ice
    • mapped through IR
  39. What is hot gas mapped with?
  40. What does the velocity of the Milky Way disk stars and gas as a function of radius show?
    The disk is not rotating with Keplerian orbits like the planets do, but there is a lot of dark matter at all radii
  41. Examples of large spiral galaxies which have rotating disks and spiral arms?
    Andromeda and the Milky Way
  42. Other galaxies that are red and have old stars are...?
    Elliptical and not rotating, no star formation
  43. What did Hubble make based on the shape of galaxies?
    • tuning fork
    • hoped this would be useful like the HR Diagram for stars
  44. Some spirals have what in the middle?
  45. Who first found evidence for dark matter?
    Fritz Zwicky, coined term supernova, interested in morphological astronomy
  46. What are Schwarzschild black holes?
    Non-rotating black holes, singularity and event horizon, photons get trapped in their photon sphere
  47. What is a Kerr black hole?
    rotating black hole, singularity becomes a ring
  48. What are wormholes?
    Discussed in scifi, places where two naked singularities connect two points in space with a shortcut, allowing travel between them faster than the speed of light
  49. What is Hawking Radiation?
    the result of particle/antiparticle production near the black hole, where one of the particles is sucked into the black hole and the other escapes-black hole eventually evaporates
  50. Most famous binary that has a black hole?
    Cygnus X-1
  51. How much of the mass in the Milky Way is dark matter?
  52. Who discovered that the universe is expanding?
  53. What is the Hubble Law?
    galaxies are redshifted and this is proportional to their distance
  54. How is distance to galaxies measured?
    standard candles (Cepheid variable stars)
  55. What does expansion imply?
    The universe began in a Big Bang, about 13.7 billion years ago
  56. What is the Open Universe?
    Expands forever
  57. Closed universe?
    expand slower and slower, stop and recollapse
  58. The expansion actually appears to be...?
    getting faster (used bright Type 1a Supernova to measure distances to galaxies)
  59. Dark Energy?
    • This is why expansion gets faster
    • 74% of mass-energy of the universe
    • dark matter is 22%
  60. Galaxies clump together to form...?
    groups of galaxies, clusters of galaxies, and superclusters of galaxies
  61. What is astrobiology?
    the search for life on extrasolar planets
  62. What is the Drake equation used for?
    argue that there must be life on some other planet, somewhere, because there are so many stars
  63. What is Fermi?
    if there is life elsewhere, why haven't they visited Earth
  64. What does Hawking believe?
    We should lay low, alien life may be evil
  65. What did the Miller experiment show?
    amino acids and other complex organic molecules could be formed in conditions we expect to be present in the Earth soon after it was formed
  66. Where do extrasolar planets have to be in order to have life?
    Their solar system's habitable zone
  67. What is SETI?
    A search for deliberate signals from extraterrestrials
  68. What is Olber's paradox?
    Why is the sky dark at night? If the universe is infinite, the sky should be the same brightness as the surface of the sun
  69. The sky is dark at night because...
    we have a cosmological horizon
  70. What is the cosmological horizon?
    We cannot see infinitely far into the universe because the universe has a finite lifetime
  71. What is the cosmic microwave background?
    radiation (light) which is left over from the Big Bang
  72. When did the universe go from being opaque to transparent?
    • When the universe cooled enough that H and He recombined and free electrons were no longer plentiful
    • Photons streamed through the Universe
  73. Today, the CMB...?
    • has Planck or thermal spectrum of 2.7 degrees K
    • uniform in temperature over the sky
  74. What is our cluster of galaxies falling towards?
    the Great Attractor
  75. Small fluctuations in the temperature map are the result of small fluctuations in
    density of the Universe, present at the time of recombination, overdense regions formed todays galaxies and stars
  76. What is inflation?
    • The universe underwent a period of very rapid expansion shortly after the Big Bang
    • solves the horizon and flatness problems
  77. Inflation is the result of...?
    a phase transition, when the 4 forces of nature started to separate from the grant unified force
  78. Subsequently, the universe was made up of
    • free quarks
    • When the universe cooled, the quarks coalesced to form protons, antiprotons, and neutrons
  79. For the first 3 minutes of the universe...?
    hot and dense, He produced by nuclear fusion
  80. The future of the universe depends on...?
    • the nature of dark energy
    • it will get progressively colder and darker, stars will stop shining, black holes will evaborate, protons will decay, and we will be left with a very dark and sparse universe