Ast 111 last test

Card Set Information

Ast 111 last test
2013-04-08 11:55:53
April 9th

last test
Show Answers:

  1. how we may find the distance to nearby stars with the method of Stellar Parallax
    • The small annual shifts in star's apparent position caused by Earth's motion around the sun.
    • Comparing observations of nearby star made 6 months apart
    • If we know the stars precise amount of shift 
    • distant stars have smaller Parallax angle
  2. What are parallax angles measured as?
  3. What is an arcsecond
    • 1/60 of an arc minute
    • 1/3600 of 1 degree
  4. What is a parsec
    distance in parsec = 1/p

    P = parallax angle in seconds

    distance to an object with a parallax angle of 1 arcsecond; approximately equal to 3.26 light years
  5. Light year
    The distance light takes to travel in a year
  6. Stellar magnitude
    • Measure the brightness of stars on a scale of stellar magnitudes
    • Ancient Greeks made sky maps 
    • #1=very bright, #6 faintest you can see my eye
  7. Today's Stellar Magnitudes
    • 5 different magnitudes
    • factor in brightness of 100
    • EX #1 is 100x brighter than #6
  8. Apparent Magnitude
    How bright a star appears to be on the sky
  9. Absolute magnetude
    Measure the intrinsic brightness of the star
  10. At what distance would a star’s apparent magnitude equal its absolute magnitude?
    10 parsecs away
  11. Apparent Magnitude of sun vs. Absolute magnitude
    • Apparent = -26.7
    • Absolute = +4.5
  12. spectraltype
    Astronomers use the various absorption lines in the spectrum of a star to define
  13. Absorption spectra of starts
    original classification system based on strength of the hydrogen absorption lines
  14. early spectra types
    • A very strong H absorption lines
    • P very weak H absorption lines
  15. What do we know governs what spectra looks like more than anything else
  16. Who started the classification system today?
    Annie J. Cannon
  17. Spectra types today
    • hottest - cool stars
    • o0-o9 b0-b9
    • The sun is a G2
    • A type stars have the strongest H absorption lines