light year and doppler effect
Post on 27-Jun-2015
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Light Year
• A measure of distance
• Distance light travels in one year
What is it?
So are we looking at the past?
5.86 x 1012 miles
We are!Imagine looking at a star 30 LY’s away. What does that number mean? For an object 30 LY’s away it takes light 30 years
to travel to your eye. How old would you be?For an object 130 LY’s away it takes light 130 years
to travel to your eye. How old would you be?For an object 457630 LY’s away it takes light
457630 years to travel to your eye. How old would you be?
43 or 44 years
143 or 144 years
457643 or 457644 years
Light Years
If a star is 30 LY’s away and the light left that star today it would not arrive at your eye for 30 years.
(So, what you are looking at is 30 years in the past!!)
Doppler Effect
Objects moving toward you appear blue or blue shifted
Objects moving away from you appear red or red shifted
Doppler Effect in Action
What is a star made of?
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