Distances in Space
MATH IN SCIENCE: EARTH SCIENCE
Objective: You will learn about the units of length used to measure distances in our solar system and
beyond and the speed of light.
Astronomical Unit
The astronomical unit (au) is the average distance from the Earth to the sun, measured to be about
1.5 x 108 km or 150,000,000 km. An AU is a convenient unit to use when discussing distances within our solar system.
Convert the following distances from either AU to km, or km to AU:
1. 2.5 AU =
_________ km
6. 750,000,000 km =
________ AU
2. 0.8 AU =
_________ km
7. 3.2 × 1011 km =
________ AU
3. 5.4 AU =
_________ km
8. 4.8 × 108 =
________ AU
4. 1.5 AU =
_________ km
9. 63,000,000 =
________ AU
5. 3000 AU =
_________ km
10. 540,000 =
________ AU
Word Problems
1. Saturn has an average distance of 9.5 AU’s from the sun. How many kilometers is this? How many meters?
2. Pluto, the dwarf planet in the solar system, is about 6 x 109 km from the sun. How many astronomical units
(AU) is this?
Light-year
The light-year (ly) is defined as the distance that light travels in a year. It is equal to a distance of approximately
9.5 x 1012 km or 9,500,000,000,000 km. A ly is a convenient unit to use when discussing distances beyond
our solar system.
Convert the following distances from either ly to km, or km to ly:
1. 5 ly =
_________ km
6. 4.73 × 1013 km =
________ ly
2. 0.75 ly =
_________ km
7. 2.838 × 1014 km =
________ ly
3. 12.3 ly =
_________ km
8. 750,000,000,000 =
________ ly
4. Proxima Centauri, the closest star to the Earth after the sun, is 4.3 light-years from us. How long does it take
light from this star to reach us?
5. The star Betelgeuse, meaning “armpit of the giant,” is 2.93 × 1015 km from Earth. How many years does it
take light from Betelgeuse to reach Earth?
6. Light from Barnard's Star, takes approximately 5.96 ly to reach Earth. How many kilometres away is
Barnard’s Star?
Homework: Nelson 9 Textbook: pg. 369 #1-3, 6-9, 11