luminosity, parallax, stars, spectral class

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6 Apr 2011
School
Course
Lecture 8
-luminosity: how bright- how much light the star is emitting (all)
-there are a few things u can tell by just looking at stars
colour: blackbodies (thermal radiation) temperatures, Doppler shift (moving
towards, away)
if a star is blue, we know for sure it is: we cant say for sure because it could be
hotter or its moving rapidly towards us
Parallax
-there are a great variety of techniques used to determine the distances to
stars for nearby stars, we use parallax
-a bigger jump distance difference- closer star, a smaller jump- further star
STARS- continued
-earth receives only a small fraction of the suns light
this small fraction of light that we receive is called apparent brightness or
apparent magnitude
-the amount of light received from a star falls with the square of our distance
from it
this is called: inverse square law of light
apparent brightness = luminosity/ 4(pi)(d^2)
we measure the apparent brightness
less light received, the further away the planet from the sun, more light received,
the closer the planet from the sun
-tells us how much fusion is going on in the star- brightness
-we find out the chemical composition or what the star is made of through
absorption spectrum
-Annie Jump Cannon- realized that you could get rid of most of the spectral
categories keeping only A,B,F,G,K,M and O formed a pattern
Oh, Be A Fine Girl, Kiss Me
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Document Summary

Luminosity: how bright- how much light the star is emitting (all) There are a great variety of techniques used to determine the distances to stars for nearby stars, we use parallax. A bigger jump distance difference- closer star, a smaller jump- further star. Earth receives only a small fraction of the sun"s light. this small fraction of light that we receive is called apparent brightness or apparent magnitude. The amount of light received from a star falls with the square of our distance from it this is called: inverse square law of light apparent brightness = luminosity/ 4(pi)(d^2) we measure the apparent brightness less light received, the further away the planet from the sun, more light received, the closer the planet from the sun. Tells us how much fusion is going on in the star- brightness. We find out the chemical composition or what the star is made of through absorption spectrum.

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