What does an astronomical unit primarily measure?

What does an astronomical unit primarily measure?

• A. Distance within the solar system.
• B. Distance to stars.
• C. Time for light to travel one year.
• D. Distance to the Moon.

Answer: (A)

An astronomical unit is a unit of length used to express distances within our solar system. It’s defined by the average distance from the Earth to the Sun, so 1 AU is about 149.6 million kilometers. This makes it easy to compare how far planets lie from the Sun or from Earth without constantly converting to kilometers. It isn’t used for measuring distances to stars (those are given in parsecs or light-years) and it’s not a time measure (that would be a year or a light-year). The Moon’s distance, for example, is only a tiny fraction of an AU, showing that the AU serves as a convenient scale for solar-system distances.

An astronomical unit is a unit of length used to express distances within our solar system. It’s defined by the average distance from the Earth to the Sun, so 1 AU is about 149.6 million kilometers. This makes it easy to compare how far planets lie from the Sun or from Earth without constantly converting to kilometers. It isn’t used for measuring distances to stars (those are given in parsecs or light-years) and it’s not a time measure (that would be a year or a light-year). The Moon’s distance, for example, is only a tiny fraction of an AU, showing that the AU serves as a convenient scale for solar-system distances.