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light-year |
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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-yearDistance 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. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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A resident of the constellation Leo, the newly discovered galaxy called Leo T is only about 600 light-years across--about one-sixteenth the diameter of the Milky Way--and 50,000 times brighter than the sun. Astronomers recently found an additional 20 star systems that lie within just 33 light-years of Earth. Launched into space in 1990, the eye in the sky snaps pictures of stars, galaxies, and planets thousands of light-years from Earth. |
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Light-years
