light-year

Home > ... > Science and Technology > Astronomy and Space Exploration > Astronomy: General > ...

Essential reading Compare
side-by-side World Encyclopedia The Columbia Encyclopedia, Sixth Edition

light-year

light-year in astronomy, unit of length equal to the distance light travels in one sidereal year . It is 9.461 × 10 ¹² km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars nearest our solar system, are about 4.3 light-years distant. See also parsec .

Create a link to this page

Copy and paste this link tag into your Web page or blog:

<a href="http://www.encyclopedia.com/topic/.aspx#1E1-lightyea" title="Facts and information about light-year">light-year</a>

Give this article a thumbs-up on StumbleUpon

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"light-year." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. 24 Dec. 2009 <http://www.encyclopedia.com>.

"light-year." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. (December 24, 2009). http://www.encyclopedia.com/doc/1E1-lightyea.html

"light-year." The Columbia Encyclopedia, Sixth Edition. 2008. Retrieved December 24, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-lightyea.html

Learn more about citation styles

light-year

World Encyclopedia | 2005 | Â© World Encyclopedia 2005, originally published by Oxford University Press 2005. (Hide copyright information) Copyright

light-year Unit of astronomical distance equal to the distance travelled in free space or a vacuum by light in one tropical year. One light-year is equal to 9.4607 × 10¹² km (5.88 × 10¹² mi).

Create a link to this page

Copy and paste this link tag into your Web page or blog:

<a href="http://www.encyclopedia.com/topic/.aspx#1O142-lightyear" title="Facts and information about light-year">light-year</a>

Cite this article
Pick a style below, and copy the text for your bibliography.

MLA
Chicago
APA

"light-year." World Encyclopedia. 2005. Encyclopedia.com. 24 Dec. 2009 <http://www.encyclopedia.com>.

"light-year." World Encyclopedia. 2005. Encyclopedia.com. (December 24, 2009). http://www.encyclopedia.com/doc/1O142-lightyear.html

"light-year." World Encyclopedia. 2005. Retrieved December 24, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-lightyear.html

Learn more about citation styles

Related entries from encyclopedias, dictionaries and thesauruses

Rate these entries|See all related entries

Free newspaper and magazine articles

	Light beer scorecard, year-to-date ending June 28th 2009. Magazine article from: Modern Brewery Age; 7/21/2009
	Traffic lights: What Leighton people want. Newspaper article from: Leighton Buzzard Observer (Leighton Buzzard, England); 9/4/2007
	Red lights mean stop: running red lights is risky, and FHWA and its partners are working hard on solutions. Magazine article from: Public Roads; 9/1/2002

Facts and information from other sites

Related articles from newspapers, magazines, and more

	Light beer scorecard, year-to-date ending June 28th 2009. Magazine article from: Modern Brewery Age; 7/21/2009; 700+ words ; Light Beer Scorecard, Year-to-date ending June 28th 2009 Excerpted from IRI Data Total US Food Drug and Convenience Case Case Sales Light Beer/ Light Pkg Type Sales % Chg YA CATEGORY--BEER 595,625,536 (0...
	LIGHTS OUT Popular Quiet Waters Park sculpture removed Newspaper article from: Capital (Annapolis); 12/28/2006; ; 700+ words ; Five years after setting sail in...Park field, "Hunting Light" has been scuttled...people noticed Hunting Light. "I hadn't realized...who was born the same year the sculpture was built...enamoured with Hunting Light. "She was captain...
	Lights out : city lights are erasing the stars, wasting energy, and hurting wildlife. Find out what's being done to darken the night.(PHYSICAL LIGHT POLLUTION) Magazine article from: Science World; 4/2/2007; ; 700+ words ; ...invented a long-lasting light bulb that was bright...night into day. Thirty years ago, astronomers were...light pollution. NIGHT LIGHTS Light pollution is caused...approximately $10 billion per year in energy expenses...Over millions of years, animals have come to...director ...
	Lighter collectors no match for new flight security rules. Newspaper article from: Chicago Tribune (Chicago, IL); 5/9/2005; 700+ words ; ...always had problems, but now lighter collectors have to deal with...Britain tried using a match to light his explosives-laden shoe...been successful had he used a lighter, prompted the lighter ban...of the Texas-based On the Lighter Side, said lighters, in essence...chronicle the last 100 ...
	Lights out Magazine article from: Sporting News; 2/9/2004; ; 700+ words ; ...Patriots offensive tackle MATT LIGHT shut down Panthers defensive...nifty postseason trifecta for Light, who suffered a high ankle...the AFC championship game two years ago and was able to play only...half of Super Bowl 36. This year, he came into the Super Bowl...man. That means good," said ...
	Lights out -- but at a price. Newspaper article from: Las Cruces Sun-News (Las Cruces, NM); 8/18/2007; 700+ words ; ...dozen mercury vapor lights at the mid-town...a portion of the light spectrum, making...lights earlier this year, 10 years after the council...for the last 10 years have been relatively...replace the 30-year-old lights to...planets hundreds of light years ...
	The Lights Before Christmas; From Styles to Colors to Cost, Options Abound for Holidays Newspaper article from: The Washington Post; 12/20/2008; ; 699 words ; ...both inside and out. Colored lights' popularity rises and falls...traditional ceramic holiday lights (the large bulbs popular 25 to 30 years ago), as well as crystal...aplenty: There are icicle light sets, for porches and fascia; rope lights, to wrap around trees; and...
	LIGHTS STILL ON. Magazine article from: Beverage Dynamics; 5/1/2001; ; 700+ words ; Light beers continue to shine...s turning out the lights. The fact is, when...brewers and retailers. Light beer volume grew more than 5% last year, with domestic lights growing to more than 1.2 billion cases. Light beers also continue...market in the next five years. "Low-calorie ...
	Tactical Lights and Techniques for Patrol Officers Magazine article from: Tactical Response; 11/1/2008; ; 700+ words ; ...officers had very few options to light up the midnight shift. The...anyone. Current tactical lights are lighter, tougher, brighter, and...flashlights of the past. Tactical lights can be mounted on chargers...options allow varied low-light encounter tactics that far...of their power over a ...
	SUReFiRe Lights and tRaining Magazine article from: Tactical Response; 11/1/2006; ; 700+ words ; ...head designer for the SureFire lights and has been the one responsible...find its way into a SureFire light is made to these stringent...feel so strongly about these lights that they are covered by a...that were made more than 20 years ago. the ultimate light As has been stated, SureFire...