Ast 111 last test

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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?
Arcseconds
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
Temperature
16. Who started the classification system today?
Annie J. Cannon
17. Spectra types today
• OBAFGKM
• hottest - cool stars
• o0-o9 b0-b9
• The sun is a G2
• A type stars have the strongest H absorption lines
 Author: summer.sproull ID: 212151 Card Set: Ast 111 last test Updated: 2013-04-08 15:55:53 Tags: April 9th Folders: Description: last test Show Answers: