Definition of astronomical unit in English:

astronomical unit

(also AU)


  • A unit of measurement equal to 149.6 million kilometres, the mean distance from the centre of the earth to the centre of the sun.

    • ‘Bodies that formed from the Sun out to a distance of about 2.5 astronomical units are primarily rocky and metallic.’
    • ‘Typical distances from the Sun are 10,000 astronomical units, and typical orbital periods are on the order of 1 million years.’
    • ‘Today the distance between the Earth and sun, known as an astronomical unit, is accurately measured by radar.’
    • ‘Because the relative distances to the planets were well known, a definitive astronomical unit allowed the actual distances to be calculated.’
    • ‘These stars are generally separated by distances of several astronomical units or more.’
    • ‘Even at its closest, Sedna comes no nearer to the Sun than 76 astronomical units, each AU equaling the average distance of the Earth from the Sun.’


astronomical unit