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Astronomy & Space vocabulary · The Night Sky & Measurement

Light-year

Meaning in astronomy & space, with examples

/ˈlaɪt jɪr/nounCore term

In astronomy & space, light-year means: The distance light travels in one year, about 9.46 trillion kilometres. It is a unit of distance, not of time.

In Turkish: ışık yılı

How it is used

Used in popular science, documentaries and news to give distances to stars and galaxies. Professional astronomers more often use the parsec, about 3.26 light-years. Spelled 'light-year' or 'light year'.

Example sentences

  1. Proxima Centauri, the nearest star to the Sun, is about 4.2 light-years away.

  2. The Milky Way is roughly 100,000 light-years across.

Common collocations

  • light-years away
  • billions of light-years
  • light-years across
  • measured in light-years
  • astronomical unitA 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.
  • starA huge ball of hot gas, mainly hydrogen and helium, that produces light and heat through nuclear reactions in its core. The Sun is the nearest star to Earth.
  • galaxyAn enormous system of stars, gas, dust and dark matter held together by gravity. A large galaxy can contain hundreds of billions of stars.
  • Milky WayThe barred spiral galaxy that contains our solar system and a few hundred billion stars. It also names the pale band of light it forms across a dark night sky.

More terms: The Night Sky & Measurement

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