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parsec |
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parsec (pär`sĕc) [parallax + second], in astronomy, basic unit of length for measuring interstellar and intergalactic distances, equal to 206,265 times the distance from the earth to the sun, 3.26 light-years, or 3.08 × 1013 km (about 19 million million mi). The distance in parsecs of an object from the earth is the reciprocal of the parallax parallax (pâr`əlăks) ..... Click the link for more information. of the object. The nearest star, Proxima Centauri, has a parallax of 0.763" of arc and a distance of about 1.31 parsecs. parsecUnit of measure used by astronomers to express distances to stars and galaxies. It is the distance at which the radius of Earth's orbit would subtend an angle of one second of arc, so an object one parsec away would have a parallax of one second. An object's distance in parsecs is the reciprocal of its parallax in seconds of arc. For example, Alpha Centauri, with a parallax of 0.76 second, is 1.33 parsecs from the Sun and Earth. One parsec equals 3.26 light-years, or 19.2 trillion mi (30.9 trillion km). parsec a unit of astronomical distance equal to the distance from earth at which stellar parallax would be 1 second of arc; equivalent to 3.0857 × 1016 m or 3.262 light years
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Pennypacker says that on the basis of observations made so far, they have calculated a "preliminary' value of the Hubble constant to be 100 kilometers per second per kiloparsec. quoted the distance to 1987A as 50 kiloparsecs or 1. It would be capable of measuring parallaxes of objects at kiloparsec distances with 10 percent accuracy. |
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