The unit AU is commonly used to express which distance?

The unit AU is commonly used to express which distance?

• A. The distance from Earth to Neptune
• B. The average distance from Earth to the Sun
• C. The distance from Earth to Mars
• D. The distance from the Sun to the galaxy center

Answer: (B)

An astronomical unit is a practical ruler for distances in our solar system. It is defined as the average distance from Earth to the Sun, about 149.6 million kilometers (93 million miles). This unit is especially handy because planets’ distances are often described relative to the Sun, so using AU keeps the numbers small and easy to compare. Therefore, the distance most commonly expressed in astronomical units is the Earth–Sun distance. Distances to other bodies, like Neptune or Mars, can be described in AU as well, but the standard reference is Earth’s distance to the Sun, and distances to the galaxy center are measured in much larger units like parsecs or light-years.

An astronomical unit is a practical ruler for distances in our solar system. It is defined as the average distance from Earth to the Sun, about 149.6 million kilometers (93 million miles). This unit is especially handy because planets’ distances are often described relative to the Sun, so using AU keeps the numbers small and easy to compare. Therefore, the distance most commonly expressed in astronomical units is the Earth–Sun distance. Distances to other bodies, like Neptune or Mars, can be described in AU as well, but the standard reference is Earth’s distance to the Sun, and distances to the galaxy center are measured in much larger units like parsecs or light-years.