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?