Notes - What Is An AU and Light Year?
Learning Target(s):
E5.p1C – Explain how a light year can be used as a distance unit.
How Far Is Earth From The Sun?
Perihelion (closest) – 91,400,000 miles
Aphelion (farthest) – 94,500,000 miles
Average Distance – 92,955,820 miles
How Far Is Earth From The Sun?
The Distance From The Sun to Earth Is Known As 1 AU (astronomical unit)
1AU = 93,000,000 miles
What’s An Astronomical Unit? (Better Known As An AU)
An Astronomical Unit is approximately the mean (average) distance between the Earth and the Sun. It is a unit that is constant (never changing) and used to indicate distances within the solar system.
So, How Do We Calculate An AU?
To calculate an AU is very simple. All you need to know is the distance between two objects (such as planets) and divide that distance by 93,000,000 miles. That’s how you get an AU.
So, Lets Practice!!!
How many AU’s is it from Hamilton to Holland?
The distance between Hamilton and Holland is approx. 9.8 miles.
How many AU’s does that equal?
93,000,000 miles
9.8 miles (distance between Hamilton/Holland)
0.000000105 A.U.’s
From Hamilton To Holland
So, Lets Try Another One!!!
How many AU’s is it from our planet (Earth) to our Moon (Luna)?
The distance between Earth and Luna is approx. 250,000 miles.
How many AU’s does that equal?
93,000,000 miles
250,000 miles (distance between Moon/Earth)
0.00269 A.U.’s
From Earth To The Moon
What’s A Light Year?
Other than using AU’s to measure space distances, we also use light years to measure distances that are too far way for us to really understand such large numbers.
A light year is a distance that tells us how far light can travel in one year!
So, How Far Can Light Travel In A Year?
Light travels at 186,000 miles per second (300,000 kilometers per second).
A light year is the distance that light can travel in a year:
��
X
X
X
X
60 seconds/minute
60 minutes/hour
24 hours/day
365 days/year
5,865,696,000,000 miles/year
186,000 miles/second
How Far Away Is Our Second Closest Star?�(The Sun is our closest star)��Our second closest star is 4 light years away and it is a triple star called Proxima Centauri��How many miles way is Proxima Centauri from Earth?�4 x 5,865,696,000,000 miles/year
23,462,780,000,000 miles away!
Recap!!!��A light year is a unit of measurement used to measure distances �(very large distances) in space!