1 AU is defined as which of the following?

1 AU is defined as which of the following?

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

Answer: (D)

An Astronomical Unit is a length used to express distances within the solar system. It is defined by the mean (average) distance from the Earth to the Sun, because Earth’s orbit is elliptical and its distance to the Sun changes over the year. Using the average distance provides a convenient, consistent scale for comparing where planets lie. So 1 AU is about 149.6 million kilometers. This unit makes it easy to say a planet is a few AU away from the Sun rather than giving huge numbers in kilometers. The other options refer to distances to other bodies, not the standard baseline for solar-system distances.

An Astronomical Unit is a length used to express distances within the solar system. It is defined by the mean (average) distance from the Earth to the Sun, because Earth’s orbit is elliptical and its distance to the Sun changes over the year. Using the average distance provides a convenient, consistent scale for comparing where planets lie. So 1 AU is about 149.6 million kilometers. This unit makes it easy to say a planet is a few AU away from the Sun rather than giving huge numbers in kilometers. The other options refer to distances to other bodies, not the standard baseline for solar-system distances.