Light-year

Light-year
Map showing stars and star systems lying within 12.5 light-years of the Sun[1]
General information
Unit systemastronomy units
Unit oflength
Symbolly[2]
Conversions
1 ly[2] in ...... is equal to ...
   metric (SI) units   
  • 9.4607×1015 m
  • 9.46073 Pm
   imperial and US units   
  • 5.8786×1012 mi
   astronomical units   

A light-year, alternatively spelled light year (ly), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km, which is approximately 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year (365.25 days).[2] Because it includes the word "year", the term is sometimes misinterpreted as a unit of time.[3]

The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist contexts and popular science publications.[3] The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years).[2]

  1. ^ "The Universe within 12.5 Light Years – The Nearest stars". www.atlasoftheuniverse.com. Retrieved 2 April 2022.
  2. ^ a b c International Astronomical Union, Measuring the Universe: The IAU and Astronomical Units, retrieved 10 November 2013
  3. ^ a b Bruce McClure (31 July 2018). "How far is a light-year?". EarthSky. Retrieved 15 October 2019.

From Wikipedia, the free encyclopedia · View on Wikipedia

Developed by Nelliwinne