astronomical unit

noun

: a unit of length used in astronomy equal to the mean distance of the earth from the sun or about 93 million miles (150 million kilometers)

Examples of astronomical unit in a Sentence

Recent Examples on the Web

That is, with Venus and earth-like planets at habitable distances from their stars as well as gas giants orbiting at Jupiter-like distances (which in our solar system’s case is 5 astronomical units), or five times the average distance between the Earth and sun. —Bruce Dorminey, Forbes.com, 19 Sep. 2025

One astronomical unit, is the distance from the sun to Earth. —Jenna Prestininzi, Freep.com, 17 Sep. 2025

At a distance of just two astronomical units from its host star (twice the distance between Earth and the sun), the planet candidate, if confirmed, would be the closest to its host star ever imaged. —Stefanie Waldek, Space.com, 7 Aug. 2025

Read More: Our Solar System May Have a New Dwarf Planet Orbiting Even Farther Than Pluto Crowded Clusters and Far-Flung Planets Though some planets orbit their stars closely, there are some planets that circle their stars from afar, from hundreds or thousands of astronomical units (AU) away. —Sam Walters, Discover Magazine, 28 May 2025

Word History

First Known Use

1848, in the meaning defined above

Rhymes for astronomical unit

• lunate
• multiunit
• subunit

Kids Definition

astronomical unit

noun

: a unit of length used in astronomy equal to the average distance of the earth from the sun or about 93 million miles (150 million kilometers)