Alpha Centauri(redirected from HD 128620)
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Alpha Centauri(ăl`fə sĕntôr`ē), brightest star in the constellation CentaurusCentaurus
, southern constellation located N and E of Crux, the Southern Cross. It is known especially for its bright stars Alpha Centauri and Hadar. It also contains Centaurus A, a radio galaxy, as well as a globular star cluster visible to the naked eye.
..... Click the link for more information. and 3d-brightest star in the sky; also known as Rigil Kent or Rigil Kentaurus; 1992 position R.A. 14h39.1m, Dec. −60°49'. Its 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
..... Click the link for more information. is −0.26. Alpha Centauri is actually a triple-star system, the components being designated A, B, and C. Alpha Centauri A is the brightest component; it is a yellow main-sequence star of the same 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.
..... Click the link for more information. (G2 V) as the sun and of about the same size and mass. It forms a binary system with the somewhat smaller, less bright, and more orange Alpha Centauri B. Alpha Centauri C, a red dwarf, is also called Proxima Centauri because it is the closest star to the earth (other than the sun), at a distance of 4.28 light-years; components A and B are currently 4.34 light-years away. Proxima Centauri orbits about the common center of mass of the system with a period of more than 250,000 years, so that in about 125,000 years it will be more distant than A and B. In 2012 the discovery of a roughly earth-sized planet orbiting Alpha Centauri B was announced; the planet was reported to orbit the star closer than Mercury orbits the sun. A roughly earth-sized planet has also been identified (2016) orbiting Proxima Centauri. Though it orbits its star much more closely than the Mercury does the sun, it is believed to be in the habitable zone because of the cooler temperatures of Proxima Centauri; however, the star is of a type that tends to produce solar flares readily, which would bombard the nearby planet with high levels of radiation and strip any atmosphere from it.
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Alpha Centauri(sen-tor -ÿ, -ee) (Rigil Kentaurus; α Cen) A binary star that is the brightest star in the constellation Centaurus, one of the brightest in the sky, and the second nearest star to the Sun. The two components, A and B, form a yellow-orange visual binary (separation 17″.7, period 80.1 years) and are similar in mass and size to the Sun. Proxima Centauri appears to be physically associated with α Cen; it is the nearest star to the Sun. mv : –0.01 (A), 1.33 (B), –0.27 (AB); Mv : 4.4 (A), 5.7 (B), 4.1 (AB); spectral type: G2 V (A), K1 V (B); mass: 1.09 (A), 0.89 (B) times solar mass; distance: 1.33 pc.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
Alpha Centauri[¦al·fə sen′tȯ·rē]
A double star, the brightest in the constellation Centaurus; apart from the sun, it is the nearest bright star to earth, about 4.3 light-years away; spectral classification G2. Also known as Rigil Kent.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
brightest star in Centaurus constellation; closest star to Earth. [Astronomy: NCE, 74]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.