Space Chapter 9

  1. what is the milky way?
    the galaxy that includes the solar system; appears as a hazy white band in the night skyImage Upload 1
  2. what is a galaxy?
    • a huge collection of stars, planets, gas and dust held together by gravity
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  3. what is a star cluster?
    • a collection of stars held together by gravity
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  4. what is an open cluster?
    a collection of 500-1000 stars, open clusters appear along the main band of the milky wayImage Upload 4
  5. what is a globular cluster?
    • a collection of 100 000 to a million stars, appear in distinctive spherical shape; globular clusters appear around the centre of the milky way
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  6. what is a local group?
    • the small group of galaxies that include the milky way (about 40)
    • diameter is about 10 million light years
  7. what is a supercluster?
    • a gigantic cluster of 4 to 25 clusters of galaxies, which is hundreds of millions of light years in size
    • there may be more than 125 billion galaxies, nearly all of them are organized in clusters
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  8. what is cosmology?
    the study of the universe; ones who study it are cosmologists
  9. what is the doppler effect?
    • the change in frequency of a light source due to its motion relative to an observer, also the change in pitch of a sound due to the motion of the source relative to the observer
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  10. what is redshift?
    the effect in which objects moving away from an observer have their wavelengths lengthened, towards the red end of the spectrum Image Upload 8
  11. what is blueshift?
    • the effect in which objects moving towards the observer hacve their wavelengths shortened, towards the blue end of the spectrum¬†
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  12. what is the big bang?
    the event that triggered the explosion of the universe 14 billion years ago
  13. what is cosmic microwave background(CMB) radiation?
    • the radiation left over from the big bang, which fills the universe
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  14. what is dark matter?
    • accounts for 23% of the universe
    • the most abundarnt form of matter in the universe, invisible to telescopes
    • its true identity is unknown
    • the search for dark matter has been going on since the 1990s
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  15. what is dark energy?
    a form of energy that makes up nearly three quarters of the universe (73%); has the effect on increasing the expansion of the universe
  16. what are the shapes of the galaxies?
    • classified as spiral or elliptical, according to shape and appearance
    • galaxies that do not fit under those categories are irregular galaxies
    • -spiral galaxy;looks like a pinwheel from above, arms spiralling out from core, looks like a plate with a bulge in the middle from the side,¬†
    • -elliptical range from a perfect sphere shape to a stretched ellipse, contain some of the oldest stars in the universe, largest galaxies are elliptcal, it is estimated that well over half are elliptical
    • - irregular galaxies do not have a regular shape (eg. plate with bulge, arms branching out, elliptical shape) made up of newly forming stars and old starsImage Upload 12
Card Set
Space Chapter 9
Space Chapter 9