Albireo

Albireo æl'bɪriou is a double star designated Beta Cygni (β Cygni, abbreviated Beta Cyg, β Cyg). The International Astronomical Union uses the name "Albireo" specifically for the brightest star in the system. Although designated 'beta', it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni and is the fifth-brightest point of light in the constellation of Cygnus. Appearing to the naked eye to be a single star of magnitude 3, viewing through even a low-magnification telescope resolves it into its two components. The brighter yellow star, itself a very close binary system, makes a striking colour contrast with its fainter blue companion. β Cygni (Latinised to Beta Cygni) is the system's Bayer designation. The brighter of the two components is designated β1 Cygni or Beta Cygni A and the fainter β2 Cygni or Beta Cygni B. The system's traditional name Albireo is a result of misunderstanding and mistranslation. It is thought that it originated in the Greek name ornis for the constellation of Cygnus, which became in Arabic. When translated into Latin, this name was thought to refer to the Greek name Erysimon for the plant called Hedge Mustard (Sisymbrium officinale, which in Latin is ireo), and so was described in Latin in the Arabo-Latin Almagest of 1515 as "Eurisim: et est volans; et jam vocatur gallina. et dicitur eurisim quasi redolens ut lilium ab ireo" ("Eurisim: and it is the flyer, and now it is called the hen, and it is called Eurisim, as if redolent like the lily from the 'ireo'"), via a confusion between ireo and the scented flower Iris florentina. This was variously miscopied, until "ab ireo" was treated as a miscopy of an Arabic term and changed into . In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Albireo for β1 Cygni. It is now so entered in the IAU Catalog of Star Names.