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Astronomy & Space vocabulary · The Night Sky & Measurement

Astronomical unit

Meaning in astronomy & space, with examples

nounCommon term

In astronomy & space, astronomical unit means: A unit of distance equal to the average distance between Earth and the Sun, about 149.6 million kilometres. It is usually written AU or au.

In Turkish: astronomik birim, AB

How it is used

Used for distances inside the solar system and in other planetary systems, where kilometres give huge numbers and light-years tiny ones. Mission updates say, for example, that a probe is 160 AU from the Sun.

Example sentences

  1. Jupiter orbits the Sun at a distance of about 5.2 astronomical units.

  2. Voyager 1 is now more than 160 astronomical units from the Sun.

Common collocations

  • one astronomical unit
  • measured in astronomical units
  • at a distance of 5 AU
  • light-yearThe distance light travels in one year, about 9.46 trillion kilometres. It is a unit of distance, not of time.
  • solar systemThe Sun and everything that orbits it: eight planets and their moons, dwarf planets, asteroids, comets, dust and gas.
  • orbitThe curved path that an object such as a planet, moon or satellite follows around another object because of gravity. As a verb, it means to move along this path.
  • SunThe star at the centre of our solar system. Its gravity holds the planets in their orbits, and its light and heat make life on Earth possible.

More terms: The Night Sky & Measurement

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