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Albireo (Beta Cygni)

Region around Albireo
Region of the Milky Way around Albireo
Albireo (Beta Cygni) is the third brightest star in the constellation Cygnus and widely regarded as one of the most attractive double stars in the sky. Its name is of uncertain provenance, having first appeared in a 1515 translated edition of Ptolemy's Almagest as ab ireo – far from the original Arabic name Al Minhar al Dajajah, meaning "hen's beak." Albireo's stellar duet, separated by 35", makes a striking gold-blue contrast, easily seen at low telescopic power. Beta1 is an orange giant K star (visual magnitude 3.1, surface temperature 4,100 K, luminosity 100 Lsun, radius 20 Rsun), while its partner, Beta2 is a main-sequence B star (visual magnitude 5.1) that is slightly variable, rapidly-rotating, losing matter, and surrounded by a gas disk of its own making. The two rotate around each other at a distance of about 4,400 AU and with a period of about 75,000 years. Beta1 itself a binary system consisting a B dwarf in a tight orbit around an aging giant.

visual magnitude 2.90
absolute magnitude -2.32
spectral type (K3II + B8V) + B9V
distance 385 light-years (118 pc)
position R.A. 19h 30m 43.3s,
Dec. +27 57' 35"
other designations 6 Cyg, HR 7417, HD 183912,
SAO 87301, BD +27 3410,
FK5: 732, WDS 19307+2758A,
NSV 12105

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