Arcturus

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Arcturus

(ärkto͝or`əs), brightest star in the constellation BoötesBoötes
[Gr.,=the herdsman], northern constellation located to the SE of the Big Dipper in Ursa Major and W of Corona Borealis, the Northern Crown. It contains the brilliant orange star Arcturus.
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 and 4th-brightest star in the entire sky; Bayer designation Alpha Boötis; 1992 position R.A. 14h15.3m, Dec. +19°13'. An orange giant of spectral classspectral class,
in astronomy, a classification of the stars by their spectrum and luminosity. In 1885, E. C. Pickering began the first extensive attempt to classify the stars spectroscopically.
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 K2 III, it has an apparent magnitudemagnitude,
in astronomy, measure of the brightness of a star or other celestial object. The stars cataloged by Ptolemy (2d cent. A.D.), all visible with the unaided eye, were ranked on a brightness scale such that the brightest stars were of 1st magnitude and the dimmest stars
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 of −0.06; its diameter is about 10 times that of the sun and its luminosity about 100 times that of the sun. Arcturus is one of the nearest giant stars, at a distance of about 36 light-years, and has one of the largest proper motionsproper motion,
in astronomy, apparent movement of a star on the celestial sphere, usually measured as seconds of arc per year; it is due both to the actual relative motions of the sun and the star through space. Proper motion reflects only transverse motion, i.e.
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 (annual angular shift in position) of the bright stars. Its name is from the Greek meaning "guardian of the bear," and it can be found by following the extension of the curve of the handle of the Big Dipper (Large Bear).

Arcturus

(ark-toor -ŭs, =tyoor -) (α Boo) A conspicuous red giant that is the brightest star in the constellation Boötes and the second-brightest star in the northern sky (after the Sun). The three stars Alioth, Mizar, and Alcaid in the handle of the Big Dipper point in its direction. Arcturus is a high-velocity star and shows spectral peculiarities. mv : –0.04; Mv : –0.2; spectral type: K2 IIIp; radius (by interferometer): 28 times solar radius; distance: 10 pc.

Arcturus

[‚ärk′tu̇r·əs]
(astronomy)
A star that is 36 light-years from the sun; spectral classification K2IIIp. Also known as α Boötes.