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Alcyone, name of the brightest star of the Pleiades

of magnitude 2.9 and spectral type B5.

It lies at a distance of about 440 light-years away. Its name comes from the mythological figure Alcyone, one of the Pleiades. Like other stars of the Pleiades it is located north of the celestial equator, in the northern hemisphere; its declination is approximately 24 ° N, so it is close enough to the celestial equator as to be observable from all populated areas of the Earth, to the Antarctic Circle.

North of the Arctic circle appears instead circumpolar, while near the Tropic of Cancer can be observed at the zenith. The best time for your observation from the middle of autumn early spring in the northern hemisphere, while the southern hemisphere is a typical object of the summer sky. Given its magnitude, equal to +2.8, it is easily visible even from urban centers moderately afflicted by light pollution. The primary component, Alcyone A, is a blue giant with an apparent magnitude of 2.85; It is an eclipsing binary and the separation between the two components is 0.031 arcsec, equal to the distance between the Sun and the planet Jupiter.

It has a brightness of 1400 times higher than that of the Sun and a temperature of 13000 K; spectral type B7 is IIIe, that is a blue giant that has emission lines. It has a mass of about 6 M, with a range estimated at 8 R. Its high speed of rotation, equal to 215 km / s, created a disk of gas orbiting the star itself at the equator, typical of Be stars, a category which Alcyone A part. Daughter of Aeolus and wife Ceyx, was changed by Zeus into a bird, when you jumped into the sea to the announcement of the death of her husband; according to another myth, the two spouses would be changed in seabirds for superbly dared called Zeus and Hera.



To open the video, click on the picture, good view from your Alessandro Brizzi.

Alcyone, name of the brightest star of the Pleiades