proper motion

Astron. the angular motion of a star relative to a suitably defined frame of reference, expressed in seconds of arc per year. Cf. tangential motion.
[1595-1605]

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Apparent motion of a star across the celestial sphere at right angles to the observer's line of sight, generally measured in seconds of arc per year.

Any radial motion (toward or away from the observer) is not included. Edmond Halley was the first to detect proper motions; the largest known is that of Barnard's star, about 10 seconds yearly.

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      in astronomy, the apparent motion of a star across the celestial sphere at right angles to the observer's line of sight; any radial motion (toward or away from the Sun) is not included. It is observed with respect to a framework of very distant background stars or galaxies. Proper motion is generally measured in seconds of arc per year; the largest known is that of Barnard's star in the constellation Ophiuchus, about 10″ yearly. The English astronomer Edmond Halley (Halley, Edmond), in 1718, was the first to detect proper motions—those of Aldebaran, Arcturus, and Sirius. The symbol for proper motion is the Greek letter μ (mu).

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Universalium. 2010.

Look at other dictionaries:

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  • proper motion — noun : the apparent change in position of a star usually expressed in seconds of arc per year that results from the projection on the celestial sphere of its motion with respect to the solar system see tangential motion …   Useful english dictionary

  • proper motion — noun Astronomy the part of the apparent motion of a star due to its actual movement in space relative to the sun …   English new terms dictionary

  • proper motion — /prɒpə ˈmoʊʃən/ (say propuh mohshuhn) noun the component of a star s motion in space which is perpendicular to the line of sight …   Australian English dictionary

  • proper motion — noun The change in apparent position of a celestial body due to that bodys velocity relative to the Sun …   Wiktionary

  • Motion — Mo tion, n. [F., fr. L. motio, fr. movere, motum, to move. See {Move}.] 1. The act, process, or state of changing place or position; movement; the passing of a body from one place or position to another, whether voluntary or involuntary; opposed… …   The Collaborative International Dictionary of English

  • Motion block — Motion Mo tion, n. [F., fr. L. motio, fr. movere, motum, to move. See {Move}.] 1. The act, process, or state of changing place or position; movement; the passing of a body from one place or position to another, whether voluntary or involuntary;… …   The Collaborative International Dictionary of English

  • proper — early 13c., adapted to some purpose, fit, apt, from O.Fr. propre (11c.), from L. proprius one s own, particular to itself, from pro privo for the individual. Proper name belonging to or relating to the person or thing in question, is from late… …   Etymology dictionary

  • proper — adj., adv., & n. adj. 1 a accurate, correct (in the proper sense of the word; gave him the proper amount). b fit, suitable, right (at the proper time; do it the proper way). 2 decent; respectable, esp. excessively so (not quite proper). 3 (usu.… …   Useful english dictionary

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