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Ast 111 last test
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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
What are parallax angles measured as?
Arcseconds
What is an arcsecond
1/60 of an arc minute
1/3600 of 1 degree
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
Light year
The distance light takes to travel in a year
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
Today's Stellar Magnitudes
5 different magnitudes
factor in brightness of 100
EX #1 is 100x brighter than #6
Apparent Magnitude
How bright a star appears to be on the sky
Absolute magnetude
Measure the intrinsic brightness of the star
At what distance would a star’s apparent magnitude equal its absolute magnitude?
10 parsecs away
Apparent Magnitude of sun vs. Absolute magnitude
Apparent = -26.7
Absolute = +4.5
spectraltype
Astronomers use the various absorption lines in the spectrum of a star to define
Absorption spectra of starts
original classification system based on strength of the hydrogen absorption lines
early spectra types
A very strong H absorption lines
P very weak H absorption lines
What do we know governs what spectra looks like more than anything else
Temperature
Who started the classification system today?
Annie J. Cannon
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
Description
last test
Updated
4/8/2013, 3:55:53 PM
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