Albireo

Lore & Background

The origin of the traditional name Albireo is unclear. Christian Ludwig Ideler traced it to Gerard of Cremona's translation of the Almagest, where the phrase 'ab ireo' may have been applied to the star at the head of the bird, later becoming 'Albireo' when an 'l' was mistakenly inserted as though it were an Arabic name. Medieval Arabic-speaking astronomers called Beta Cygni 'minqār al-dajājah' (the hen's beak), translated into Latin as 'Rostrum Gallinae'. Since Cygnus is the swan and Beta Cygni is at its head, it is sometimes called the 'beak star'.

Reader's Guide

Albireo is notable as one of the best contrasting double stars in the sky due to the amber and blue-green colors of its two main components. It is not known whether β Cygni A and B are a physical binary or merely an optical double; if physical, their orbital period is probably at least 100,000 years, but different proper motions and distances measured by Hipparcos and Gaia leave the association uncertain. The primary, β Cygni A, is itself a multiple system: it has a close companion (Ac) with a preliminary orbital period of 214 years, and in 2022 a third component (Ad) was found orbiting Aa with a 371-day period. In 2023, Gaia data confirmed a mass discrepancy in the Aa/Ac orbit, suggesting Ac may be a tight unresolved binary or contain a compact object. Albireo will become the brightest star in the night sky in about 3.87 million years, peaking at magnitude –0.53 in 4.61 million years.

Did You Know?

• Albireo is the fifth-brightest point of light in Cygnus, despite its Bayer designation 'beta'.
• The brighter component β Cygni A is itself a very close trinary system.
• In around 3.87 million years, Albireo will become the brightest star in the night sky.
• The name 'Albireo' may have originated from a mistaken insertion of an 'l' into the phrase 'ab ireo'.