Word Study
parallax second
CIDE DICTIONARY
parallax second, n.
An annual parallax of one second of an arc; -- applied to celestial objects outside the solar system. It is used to measure the distance of an astronomical object from the Earth. A star which has an annual parallax of one second of an arc is considered to be one parsec (3.26 light years) distant from the earth. See parsec in the vocabulary. [PJC]
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