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light-year

File:12lightyears.gif · Wikimedia Commons · See Wikimedia Commons

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light-year

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Also known as ly, light year, lightyear, l.y., light-years, lightyears, light years

A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion kilometres or 5.88 trillion miles. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Despite its inclusion of the word "year", the term is not a unit of time.

OverviewAI-generated

A light-year is a unit of length used in astronomy. It is defined by specific conversions to standard units. One light-year equals 9460730472580800 in one standard measure and 372469718092929000 in another. The term is also referred to as Lichtjahr in German-language physics lexicons.

The concept is documented in various reference works. It appears in the Lexikon der Physik, which contains 22573 characters. The entry is grounded in external sources and is categorized under "Light-year" on Commons. The subject is referenced by 10,526 other encyclopedia articles, indicating its widespread use in scientific literature.

Synthesized by Vinony from 9 facts across 3 sources: Wikidata, Firecrawl, Vinony graph. Generated from structured data (not the Wikipedia text) and checked against those facts — may still contain errors.

Key facts

Unit.name
light-year
Unit.standard
astronomy units
Unit.quantity
length
Unit.symbol
ly
Unit.units1
metric (SI) units
Unit.units2
imperial and US units
Unit.units3
astronomical units
Unit.caption
Map showing stars and star systems lying within 12.5 light-years of the Sun
Unit.image
300px

via Wikipedia infobox

Described at

spektrum.de →

Link to a page describing this subject · not written by Vinony

Wikidata facts

Image
1e16m comparison 10 light years sirius.png
Show 8 more facts
unit symbol
a.l.
measured physical quantity
length
conversion to SI unit
9460730472580800
conversion to standard unit
63240
Wikidata SPARQL query equivalent
wd:Q531 p:P2370/psn:P2370 [wikibase:quantityAmount ?source; wikibase:quantityUnit ?base]. ?item p:P2370/psn:P2370 [wikibase:quantityAmount ?target; wikibase:quantityUnit ?base]. BIND(?source / ?target as ?value)
on focus list of Wikimedia project
Wikipedia:Vital articles/Level/4
described at URL
www.spektrum.de/lexikon/physik/lichtjahr/9014
Commons category
Light-year
Sources (6)

via Wikidata · CC0

~11 min read

Encyclopedic overview

8 sections
Contents
  • Definitions
  • History
  • Usage of term
  • Related units
  • See also
  • Notes
  • References
  • External links

A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion kilometres or 5.88 trillion miles. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Despite its inclusion of the word "year", the term is not a unit of time.

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. The unit most commonly used in professional astronomy is the parsec (pc), approximately 3.26 light-years.

Excerpted from Wikipedia’s “light-year” article, available under the CC BY-SA 4.0 licence.

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