Light Year
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A Light Year is an length unit of measurement that is used informally to express astronomical distances.
- AKA: Light-Year.
- Context:
- It is It is approximately 9 trillion Kilometres.
- Example(s):
- a Cubic Light-Year.
- …
- Counter-Example(s):
- a Kilometer.
- See: Second of Arc, Astronomical System of Units.
References
2016
- (Wikipedia, 2016) ⇒ https://en.wikipedia.org/wiki/Light-year Retrieved:2016-7-15.
- A light-year (or light year, abbreviation: ly [1] ) is a unit of length used informally to express astronomical distances. It is approximately 9 trillion kilometres (or about 6 trillion miles).[note 1] 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). Because it includes the word year, the term light-year is sometimes misinterpreted as 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 and popular science publications. The unit usually used in professional astrometry is the parsec (symbol: pc, approximately 3.26 light-years; the distance at which one astronomical unit subtends an angle of one second of arc).
- A light-year (or light year, abbreviation: ly [1] ) is a unit of length used informally to express astronomical distances. It is approximately 9 trillion kilometres (or about 6 trillion miles).[note 1] 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). Because it includes the word year, the term light-year is sometimes misinterpreted as a unit of time.
- ↑ ISO 80000-3:2006 Quantities and Units - Space and Time, Annex C, Other non-SI units given for information, especially regarding the conversion factors (p18)
- http://www.astronomy.com/news/2016/07/more-than-1-million-galaxies-are-mapped-to-research-dark-energy
- QUOTE: In the quest for dark energy, astronomers have created an unprecedented 3D map of 1.2 million galaxies in a volume of about 650 cubic billion light years.
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