Astronomy Chapter 13

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  1. elliptical galaxy
    a galaxy that is round of elliptical in oultine and contains little gas and dust, no disk or spiral arms, and few hot, bright stars
  2. spiral galaxy
    a galaxy with an obvious disk component containing gas, dust, hot bright stars, and spiral arms
  3. barred spiral galaxy
    a spiral galaxy with an elongated nucleus resembling a bar form which the arms originate
  4. irregular galaxy
    a galaxy with a chaotic apperance, large clouds of gas and dusts, and both population I and II stars, but without spiral arms
  5. distance indicator
    object whose luminosity or diameter is known; used to find the distance to a star cluster or galaxy
  6. standard candle
    a distance indicator whose brightness is known
  7. distance scale
    a method by which astronomers use closer distance measurements to calibrate father distances to remote galaxies
  8. look back time
    the amount by which we look into the past when we look at a distant galaxy. A time equal to the distance to the galaxy in light-years.
  9. hubble law
    the linear relation between the distances to galaxies and their velocity of recession
  10. Hubble constant
    a measure of the rate of expansion of the universe. The average value of velocity of recession is divided by distance; presently blieved to be about 70 km/s/Mpc
  11. rotation curve
    a diagram showing the velocity of rotation at different distances from the center of the galaxy
  12. rotation curve method
    a method of determining a galaxy's mass by observing the orbital velocity and radius of stars in the galaxy
  13. cluster method
    the method of determining the masses of galaxies based on the motions of galaxies in a cluster
  14. gravitational lensin
    the process by which the gravitational field of a massive object focuses the light from a distant object to produce multiple images of the distant object or to make the distant object look brighter
  15. rich galaxy cluster
    a cluster containing more than 1,000 galaxies, mostly elliptical, scattered over a volume about 3 Mpc in diameter
  16. poor galaxy cluster
    an irregularly shaped cluster that contains fewer than 1,000 galaxies, many spiral, and no giant ellipticals
  17. ring galaxy
    a galaxy that resembles a ring around a bright nucleus. It is believed to be the result of a head-on collision of two galaxies
  18. starburst galaxy
    a galaxy undergoing a rapid burst of star formation
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Astronomy Chapter 13
2012-04-18 01:54:09
ASTR 205

Galaxies- key terms and concepts
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