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Fomalhaut
Fomalhaut (Alpha Piscis Austrini, Alpha PsA, α Piscis Austrini, α PsA) is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. It is a class A star on the main sequence approximately from Earth as measured by the Hipparcos astrometry satellite.〔 Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.〔 It is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk.〔 Fomalhaut, K-type star TW Piscis Austrini and M-type star LP 876-10 constitute a triple system even though the companions are separated by several degrees.〔
Fomalhaut holds a special significance in extrasolar planet research, as it is the center of the first stellar system with an extrasolar planet candidate (Fomalhaut b) imaged at visible wavelengths. The image was published in ''Science'' in November 2008.〔 Fomalhaut is the third brightest star known to have a planetary system (as viewed from Earth), after Pollux and the Sun.
==Fomalhaut A==
At a declination of −29.6°, Fomalhaut is located south of the celestial equator, and hence is best viewed from the Southern Hemisphere. However, its southerly declination is not as great as that of stars such as Acrux, Alpha Centauri and Canopus, meaning that, unlike them, Fomalhaut is visible from a large part of the Northern Hemisphere as well. Its declination is greater than that of Sirius and similar to that of Antares. At 40°N, Fomalhaut rises above the horizon for eight hours and reaches only 20° above the horizon, while Capella which rises at approximately the same time will stay above the horizon for twenty hours. From England the star never appears much brighter than magnitude 2.2 due to it being so close to the horizon, and from southern Alaska or Scandinavia it never rises above the horizon at all. Fomalhaut can be located in these northern latitudes by the fact that the western (right-hand) side of the Square of Pegasus points to it. Continue the line from Beta to Alpha Pegasi towards the southern horizon: Fomalhaut is about 45˚ south of Alpha Pegasi, with no bright stars in between.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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