Sirius


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Sirius

(sĭr`ēəs), or

Dog Star,

brightest star in the sky. It is located in the constellation Canis MajorCanis Major
[Lat.,=greater dog], constellation lying near the celestial equator, SE of Orion. Known as the Large Dog (Canis Minor is the Small Dog), it was associated with the figure of a dog by many cultures; the ancient Greeks identified it as one of Orion's hunting dogs,
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 (1992 position R.A. 6h44.8m, Dec. −16°42'); its Bayer designation is Alpha Canis Majoris. Sirius [Gr.,=scorching], having 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 −1.45, is exceeded in brightness only by the sun, the moon, and Venus and by Mars and Jupiter at their maximum brightness. A white, main-sequence star 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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 A1 V, Sirius is about twice the size of the sun and about 20 times as luminous. It is also one of the nearest stars, lying at a distance of 8.7 light-years, so that it has been studied extensively. From an analysis of its motions, F. W. Bessel concluded (1844) that it had an unseen companion, which was later (1862) confirmed by observation. The companion, Sirius B, is a white-dwarf star and has also been the object of considerable study because it is the first white dwarf whose spectrum was found to exhibit a gravitational red shiftred shift
or redshift,
in astronomy, the systematic displacement of individual lines in the spectrum of a celestial object toward the red, or longer wavelength, end of the visible spectrum. The effect was discovered by V. M. Slipher of Lowell Observatory.
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 as predicted by the general theory of relativityrelativity,
physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.
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.

Sirius

(seer -ee-ŭs, si -ree-) (Dog Star; α CMa) A white main-sequence star that is the brightest one in the constellation Canis Major and the brightest (after the Sun) and one of the nearest stars in the sky. It lies in a descending (southeasterly) line from Orion's Belt. Sirius is about 1.5 times as hot as the Sun, with a surface temperature of more than 9000 K, and is about 23 times as luminous. It is a visual binary (separation 4″.6, period 50 years), the companion, Sirius B, being the first white dwarf to be discovered. Bessel suggested (1844) that Sirius had a dark companion to account for the star's wobbling movement. With improved telescope lenses Alvan G. Clark detected (1862) a tiny companion whose spectrum, first taken (1915) by W.S. Adams Jr., identified Sirius B as a white dwarf. The spectrum demonstrated the gravitational redshift predicted by the general theory of relativity. mv : –1.46 (A), 8.3 (B); Mv : 1.4 (A), 11.2 (B); spectral type: A1 Vm (A), DA (B); mass: 2.31 (A), 0.98 (B) times solar mass; radius: 1.7 (A), 0.022 (B) times solar radius; distance: 2.65 pc.

Sirius

 

(α Canis Majoris), the brightest star in the heavens, with a visual stellar magnitude of — 1.46. Sirius has a luminosity 22 times greater than that of the sun; its distance from the sun is 2.7 parsecs. Sirius is a system of two stars: the satellite of Sirius, a star 10,000 times fainter than Sirius itself, was the first white dwarf to be discovered.

Sirius

[′sir·ē·əs]
(astronomy)
The brightest-appearing star in the sky; 8.7 light-years from the sun, spectral class A1V; it has a white dwarf companion. Also known as Dog Star.

Sirius

dog star; brightest star in the heavens. [Astronomy: EB, IX: 238]
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