vendredi 12 septembre 2008

Cygnus 2

Beta1 Cygni

Distance (Light Years) 386 ± 26
Visual Magnitude 3.05
Color (B-V) 1.13

Names For This Star

The name of this star looks Arabic, but it isn't. Actually the name of this seems to derive from the Latin phrase ab ireo applied to the constellation of Cygnus in the 1515 edition of Ptolemy's Almagest.
Description of the Star

Burnham describes Albireo as one of the most beautiful double stars in the sky, consisting of a bright "golden yellow" primary with a blue or "sapphire" companion.
The brighter star Albireo A is a K3II bright giant. This type of star is cooler than the sun, with an effective temperature of approximately 4100 K. It is probably about 20 times larger in radius than the sun and 100 times as luminous.

The The Bright Star Catalog suggests additional components at separations from A well under one sec of arc. The Hipparcos Catalog lists a C component at a separation of 0.389 seconds of arc (46 AU separation at the distance of the star). The C component is some 2 magnitudes dimmer than A.

Alpha Cygni

Distance (Light Years) 3200 ± 1800
Visual Magnitude 1.25
Color (B-V) 0.09

Names For This Star

Other names for this star are Deneb el Adige, Arided, Aridif, Gallina, or Arrioph.
The commonly recognized name Deneb is derived from the Arabic phrase Al Dhanab al Dajajah meaning "The Hen's Tail."

Arided derives from an earlier Arabic designation of the constellation. Its meaning is unclear.

Aridif and Arrioph derive from the Arabic name Al Ridf, meaning "The Hindmost", which certainly describes the star as it lies in the tail of the Swan of Cygnus.

The name "Gallina" is Latin and means "hen." It was sometimes used in the past to name the constellation, but later appeared as a name for the brightest star in the constellation.

Description of the Star

Deneb is a white A2Ia supergiant star. Assuming a distance of 1600 ly, Burnham estimates the luminosity of Deneb to be 60,000 times that of the sun. At 3200 ly, the luminosity would be nearer to 250,000 times that of the sun. Burnham estimates the mass at 20 times that of the sun.

Gienah cygni
Epsilon Cygni

Distance (Light Years) 72.06 ± 0.84
Visual Magnitude 2.48
Color (B-V) 1.03

Names For This Star

Gienah derives from the Arabic Al Janah meaning "The Wing." The star should probably be called "Gienah Cygni" to distinguish it from the Gienah in Corvus.
Description of the Star

Gienah Cygni is a cool, orange K0-III giant star 40 times as luminous as the sun. The spectral type implies a temperature of perhaps 4500 K, a mass more than 4 times that of the sun and a radius maybe 16 times greater.
Gienah has a dim 13th magnitude companion designated Gienah C lying 78 seconds of arc from the A component, corresponding to a projected distance of 1700 AU. (The B component seems not to be physically associated with the system; it is merely a background star that appears at a small angular separation from A.)

Gamma Cygni

Distance (Light Years) 1520 ± 360
Visual Magnitude 2.23
Color (B-V) 0.68

Names For This Star

Sadr, alternatively Sador or Sadir, derives from the Arabic name for the star Al Sadr al Dajajah, "The Hen's Breast."
The name of the star reflects the Arabic idea of the constellation of Cygnus, that is, as a hen rather than a swan.

Description of the Star

Sadr is a yellowish F8Ib supergiant star having a luminosity of perhaps 20,000 times that of the sun. The spectal type implies a mass about 10 times that of the sun and a diameter maybe 100 times that of the sun.

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