Which unit is commonly used to describe interplanetary distances in the solar system?

Which unit is commonly used to describe interplanetary distances in the solar system?

• A. Kilometer
• B. Meter
• C. Light-year
• D. Astronomical unit

Answer: (D)

Distances inside our solar system are most easily described with an astronomical unit because this unit is tied to the Earth’s orbit around the Sun, keeping numbers manageable. An astronomical unit is about 149.6 million kilometers, the average distance from Earth to the Sun. Using this unit, you can express planetary distances in simple terms: Mars is about 1.5 AU from the Sun, Jupiter about 5.2 AU, and Neptune around 30 AU. Using kilometers or meters becomes unwieldy for outer planets, since those numbers grow very large, while a light-year is used for distances to stars and galaxies far beyond the solar system. So the astronomical unit is the most convenient and standard way to describe interplanetary distances.

Distances inside our solar system are most easily described with an astronomical unit because this unit is tied to the Earth’s orbit around the Sun, keeping numbers manageable. An astronomical unit is about 149.6 million kilometers, the average distance from Earth to the Sun. Using this unit, you can express planetary distances in simple terms: Mars is about 1.5 AU from the Sun, Jupiter about 5.2 AU, and Neptune around 30 AU. Using kilometers or meters becomes unwieldy for outer planets, since those numbers grow very large, while a light-year is used for distances to stars and galaxies far beyond the solar system. So the astronomical unit is the most convenient and standard way to describe interplanetary distances.