Card Set Information

2014-05-12 01:58:38
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  1. The temperature of the sun's core
    15 million degrees
  2. what are sunspots
    dark spots occur where twisted magnetic field lines channel hot gases
  3. what do we learn about the solar interior from solar seismology
    densities, temperatures, and composition of inner layers are measured
  4. what is the photosphere
    the coolest part of the sun
  5. the sun's corona ejects a solar wind of particles. which partic les
  6. the rainbow of colors (wavelengths) emitted by the sun is an absorption specturm. how can we tell which elements are found in the sun
    each element has electrons that absorb/emit unique colors
  7. Which stars spend the shortest time on the main sequence
    massive stars
  8. if a star that is 30 pc away from us has apparent magnitude of 7, would the star's absolute magnitude be greater or smaller than 7
    smaller: a smaller magnitude describes a brighter object
  9. stars motion away and toward us are measured differently than motions across our field-of-view. what technique is most used to measure the speed of a star moving away from us?
    doppler shift
  10. some stars finish the main sequence in a few million years while others are not finished the main sequence after 10 billion years. which finish the main sequence first?
    blue star
  11. what describes a spectral binary pair of stars
    spectral lines periodically change wavelength due to orbiting of two stars
  12. variable stars periodically change their brightness. Cepheid variable, (CV) absolute magnitude is related to the period of variability. CV's are useful in determining the star's
  13. the most intense wavelength (color) of a main sequence star is, inversely proportional to the star
  14. blue giant stars have huge very hot core and fuse fast. why does main sequence fusion take place only in the core
    only the center is hot and dense enough
  15. if a cluster of stars has only 100-1000 stars, loosely held together by gravity, in the disk of our galaxy, and each contains many elements (like our sun) then it is a
    open cluster
  16. how do stars form
    gravity collapsed a could of gas/dust into one of more stars
  17. what describes premain sequence not yet stable stars, sometimes with variable erratic intensity or jets?
  18. what is the nature of the process that causes stars to radiate heat and light for millions or billions of years?
  19. what is a brown dwarf?
    a low mass object that can't sustain fusion like a star
  20. why are binary stars so common
    many stars form due to gravity in dense spots of the same gas clouds
  21. what happens to cause a star to become a red giant
    • hydrogen fuel becomes too cool and not dense enough to support fusion
    • gravity collapses the star to a smaller, hotter core
    • the core comes dense and hot enough to fuse helium
    • heat causes thermal expansion to a giant size
  22. what happens inside a red giant
    the core gets progressively smaller and hotter, fusing more elements
  23. what causes the balance between thermal expansion and gravity to fail in a red giant
    iron fusion requires more energy than it radiates
  24. how were earths heavy elements created
    nuclear fusion/recycling by stars
  25. a planetary nebula is misnamed because it has nothing to do with planets. where does a planetary nebula come from?
    shells of gas are ejected as a stare core collapses to form a white dwarf
  26. describe a white dwarf
    as large as earth, supported by electron degeneracy, 1 tspoon=5tons
  27. after the red giant phase, if the stellar core retains less than 1.4 solar masses, the result will be a
    white dwarf
  28. a spectacular supernova 1a increases in brightness by 20 magnitudes (a factor of a hundred million) what could cause this kind of supernova
    gas mass transfer from neighboring red giant explodes a white dwarf
  29. the core of an imploding type II supernova could become
    black hole
  30. how do we know that the crab nebula is a supernova remnant
    gas filaments are expanding rapidly
  31. what stops the gravitational implosion of a neutron star?
    neutrons pushing against neutrons
  32. if neutron stars are too small to be seen, how can we observe them
    • as they rotate, they emit radio waves along magnetic axes
    • radio emissions are seen once per star rotation
    • some neutron stars are sources of pulsar pulses
    • we can detect a neutron star in a binary pair if a visible star orbits it
  33. if a star collapses and the core has 8 or more solar masses, what prevents heat and light and gas from escaping from the collapsed black hole?
  34. How would we recognize the presence of a black hole
    • spectroscopic binary star orbiting a massive invisible star
    • many stars and clouds of gas orbiting a region in a galaxy center
    • xrays from hot material colliding as it falls through an accretion disc
  35. the schwarzchild radius is 3km/solar mass. what is the even horizan
    a distance from a central black hole within which light cannot escape
  36. assume very large uniform cloud rolled up long ago into a massive blue giant star, passing through a red giant stage to form a black hole. what is the maxiumum amount of mass (in solar masses) a black hole could have?
  37. where are the disk stars in the spiral arms of our galaxy going?
    revolving around the nucleus
  38. only ancient (old red) stars illuminate which region of the milky way
    halo of globular clusters
  39. an open cluster of stars often is found in regions of ionized gas, with some O & B stars. how many stars are in an open cluster
  40. in what band is there extreme high energy radiation from the center of the galactic nucleus?
  41. the region between the stars is filled with
    • hydrogen molecules
    • co, co2, h20, nh3, ch4, he...
  42. if we see a blue nebula near a blue star, what kind of nebula is it?
  43. what is interstellar reddening
    blue is lost by scattering through dust & gas
  44. describe a globular cluster
    old red dwarf stars > 100000 solar masses
  45. since small amounts of carbon monoxide, co are easily detected, we use CO measurements to help identify regions of the most common gas
    molecular hydrogen
  46. the most distinguishing features of galaxies are
    millions to thousand billions of stars
  47. individual stars are so far apart (compared to their size that collisions are very unlikely. compared to the size of galaxcies, the distance between the centers of galaxies in a cluster...
    is small enough that galaxies can merge
  48. explain a starbust galaxy
    a very bright agn with blue stars
  49. large spiral galaxies near us are likely to have this at their core.
    a black hole
  50. what can an active galaxy have than an ordinary galaxy doesn't have
  51. double-lobed radio structures, exceptionally bright nuclei (in radio & xray) and very high doppler recession velocities are often features of active galaxies and also
  52. how is a quasar different than an active galaxy? only quasars have
    extreme doppler shifts
  53. three demensional plots of thousands of clusters galaxies show structure that looks like
    formation on edges of voids (bubbles)
  54. hubbles law says
    dopple speeds were greatest further away and longer ago
  55. if our galaxy rotates once every 230 million years, how do we detect this motion
    proper motion & doppler shifts
  56. on the pitch fork diagram of galaxies, spiral galaxies are classified by
    spiral arm length/ width of nucleus
  57. what measurements are best for mapping quasars?
    survey of red shifts
  58. what is a quasar
    extremely bright core of a galaxy with a huge red shift
  59. quasars are relatively small objects to radiate so much energy. why isnt a quasar seen in our huge galaxy?
    our galaxys quasar may have faded
  60. which best describes gravitational lensing
    image distortion due to gravitational focusing of light by an intervening galaxy
  61. how do we know that the universe was different billions of years ago
    quasars are only very far away