light-year, in astronomy, unit of length equal to the distance light light, visible electromagnetic radiation . Of the entire electromagnetic spectrum , the human eye is sensitive to only a tiny part, the part that is called light. The wavelengths of visible light range from about 350 or 400 nm to about 750 or 800 nm.
..... Click the link for more information. travels in one sidereal year sidereal year, time required for the earth to complete an orbit of the sun relative to the stars. The sidereal year is 365 days, 6 hr, 9 min, 9.5 sec of mean solar time (see solar time ).
..... Click the link for more information. . It is 9.461 × 10¹² km (about 6 million million mi). Alpha Centauri Proxima Centauri because it is the closest star to the earth (other than the sun), at a distance of 4.28 light-years, components A and B are currently 4.34 light-years away.
..... Click the link for more information. and Proxima Centauri, the stars nearest our solar system, are about 4.3 light-years distant. See also parsec parsec (pär`sĕc) [parallax + sec
..... Click the link for more information. .

light-year

Distance traveled by light moving in a vacuum in one year, at its accepted speed of 186,282 mi/second (299,792 km/second). It equals about 5.9 trillion mi (9.5 trillion km), 63,240 astronomical units, or 0.307 parsec.

light-year [′līt ‚yir]

(astrophysics)

A unit of measurement of astronomical distance; it is the distance light travels in one sidereal year and is equivalent to 9.461 × 10¹²kilometers or 5.879 × 10¹²miles.

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light-year

light-year
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