# Worksheet: Units of Astronomy: The Astronomical Unit (AU)

In this worksheet, we will practice converting between the astronomical length unit and meters and between the astronomical length unit and light-years.

**Q1: **

What is km in AU? Give your answer to 2 significant figures.

**Q2: **

How many meters are there in 3.0 AU? Give your answer to 2 significant figures.

- A m
- B m
- C m
- D m
- E m

**Q3: **

Saturn orbits the Sun at a distance of about 9.6 AU. What is this distance in meters? Give your answer to 2 significant figures.

- A m
- B m
- C m
- D m
- E m

**Q4: **

What is m in AU? Give your answer to 2 significant figures.

**Q5: **

Mercury orbits the Sun at a distance of about m. What is this distance in AU? Give your answer to 2 significant figures.

**Q6: **

Pluto orbits the Sun at a distance of about 39 AU. How many hours does it take a beam of light from the Sun to travel this distance? Give your answer to 2 significant figures.

**Q7: **

How many kilometers are there in 210 AU? Give your answer to 2 significant figures.

- A km
- B km
- C km
- D km
- E km

**Q8: **

Which distance is larger: 200,000 AU or 17 ly?

**Q9: **

Which of the following is the correct description of how the astronomical unit is defined?

- AThe astronomical unit is a unit of length roughly equal to the distance between Earth and the Sun.
- BThe astronomical unit is a unit of length roughly equal to the distance between Jupiter and the Sun.
- CThe astronomical unit is a unit of length roughly equal to the distance between Venus and the Sun.
- DThe astronomical unit is a unit of length roughly equal to the distance between Earth and the Moon.
- EThe astronomical unit is a unit of length roughly equal to the distance between Pluto and the Sun.

**Q10: **

Proxima Centauri is the closest star to our solar system at a distance of 4.2 light-years. How far is this distance in AU? Give your answer to 2 significant figures.

**Q11: **

Which distance is larger: 1 astronomical unit or 1 light-year?

**Q12: **

What is 1 light-year in AU? Give your answer to 2 significant figures.