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 arcseconds, 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 times that of the Sun, radius 20 times that of the Sun), 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 astronomical units and with a period of about 75,000 years. Beta¹ is itself a binary system consisting a B dwarf in a tight orbit around an aging giant.