Which statement best describes the Astronomical Unit?

Which statement best describes the Astronomical Unit?

• A. The average distance between the Sun and Earth
• B. The distance light travels in a year
• C. The diameter of the Sun
• D. A measure of distance to nearby stars in light-years

Answer: (A)

The Astronomical Unit is a distance used to describe sizes within our solar system, defined as the average distance between the Sun and the Earth. Because Earth travels in an elliptical orbit, this distance varies, but it is standardized as about 149.6 million kilometers (the semi-major axis of Earth's orbit). This unit makes it easy to compare how far other planets are from the Sun, such as Mars at around 1.5 AU, Jupiter at about 5.2 AU, and Neptune near 30 AU. It’s not the distance light travels in a year (that’s a light-year), not the Sun’s diameter (about 1.39 million km), and not used for measuring distances to stars in light-years.

The Astronomical Unit is a distance used to describe sizes within our solar system, defined as the average distance between the Sun and the Earth. Because Earth travels in an elliptical orbit, this distance varies, but it is standardized as about 149.6 million kilometers (the semi-major axis of Earth's orbit). This unit makes it easy to compare how far other planets are from the Sun, such as Mars at around 1.5 AU, Jupiter at about 5.2 AU, and Neptune near 30 AU. It’s not the distance light travels in a year (that’s a light-year), not the Sun’s diameter (about 1.39 million km), and not used for measuring distances to stars in light-years.