1. Study of objects outside of Earth & its atmosphere.
ASTRONOMY 
Study of objects outside of Earth & its atmosphere.
Includes celestial objects such as:
Moons; Planets; Stars; Asteroids;
Meteors; Comets; & Galaxies

2. Measuring Distances in the Universe
Astronomical unit (AU)
Average distance from the Earth to the sun
( Km = 1AU)
Used to measure large distances (eg between planets)

3. Measuring Distances in the Universe
Light Year (ly)
Distance that a photon of light will travel in one year.
the speed of light is c = 3.0 x 108m/s
(about AU)
Used to measure distances between stars
Closest star Sun
2nd closest star Proxima Centauri
(4.25 ly away ( AU))

4. Astrolabe A two-dimensional model of the celestial sphere.
(Greek for “the one who
catches the heavenly bodies”)
An instrument used to determine:
position of celestial objects
altitude (height) of any object
over the horizon

5. Applications of Similar Triangles & Parallax

6. Geometry of Triangles
Astronomers use triangles to estimate great distances.
As early as 200 BC the Greek philosopher Eratosthenes used triangles to measure the size of our planet
He calculated the Earth’s circumference to be 40,000km & its radius to be 6366km
Today orbiting satellites calculate the
earth’s circumference to be 40,070km
& its radius 6378km

7. Triangulation
The process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline

8. Parallax: The difference in the apparent position of an object viewed along two different lines of sight

9. With parallax… If you look at the same star from two different locations on Earth at the same time, nearby stars will appear to shift in position relative to other, more distant stars.
Distant Star A
baseline
Closer Star
Distant Star B

10. OR… you can look at the same star from the same place on Earth… but at 2 different times of the year
Science In Action p.450

11. Triangulation

12. 1st - we need to use our knowledge of parallax… take a measurement of an object in space from 2 points on Earth (or from the same point at 2 different times)
that gives us 2 angles for our triangle

13. 2nd - we need to measure the base of our triangle
3rd – we need to understand trigonometry …sometime after grade 9! 

14. Instead of using trigonometry… we will create a scale diagram to figure out the distance to an object!
Let’s try it out…