Albireo is a

double star In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a bi ...

designated Beta Cygni (β Cygni, abbreviated Beta Cyg, β Cyg). The

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

uses the name "Albireo" specifically for the brightest star in the system. Although designated '

beta Beta (, ; uppercase , lowercase , or cursive ; grc, βῆτα, bē̂ta or ell, βήτα, víta) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Modern Greek, it represents the voiced labiod ...

', it is fainter than

Gamma Cygni Gamma Cygni (γ Cygni, abbreviated Gamma Cyg, γ Cyg), officially named Sadr , is a star in the northern constellation of Cygnus, forming the intersection of an asterism of five stars called the Northern Cross. Based upon parallax mea ...

Delta Cygni Delta Cygni (δ Cygni, abbreviated Delta Cyg, δ Cyg) is a binary star of a combined third-magnitude in the constellation of Cygnus. It is also part of the Northern Cross asterism whose brightest star is Deneb. Based upon parallax m ...

, and

Epsilon Cygni Epsilon Cygni (ε Cygni, abbreviated Epsilon Cyg, ε Cyg) is multiple star system in the constellation of Cygnus. With an apparent visual magnitude of 2.48, it is readily visible to the naked eye at night as one of the brighter membe ...

and is the fifth-brightest point of light in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Cygnus. Appearing to the naked eye to be a single star of

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

3, viewing through even a low-magnification

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

resolves it into its two components. The brighter yellow star, itself a very close

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that thi ...

, makes a striking colour contrast with its fainter blue companion.

Nomenclature

''β Cygni'' ( Latinised to ''Beta Cygni'') is the system's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. ...

. 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 Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

name ' for the constellation of Cygnus, which became ' in

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...

. When translated into

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, 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 The identity of the plant first described by Carl Linnaeus as ''Iris florentina'' remains unclear, . In horticulture, it has been treated as a white-flowered variant of ''Iris'' × ''germanica'', under names such as ''Iris germanica'' nothovar. ...

''. This was variously miscopied, until "''ab ireo''" was treated as a miscopy of an Arabic term and changed into '. In 2016, the

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(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. Medieval Arabic-speaking astronomers called Beta Cygni ' (English: ''the hen's beak''). The term ' (منقار الدجاجة) or ''Menchir al Dedjadjet'' appeared in the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', which was translated into

as ''Rostrum Gallinae'', meaning ''the hen's beak''. Since Cygnus is the swan, and Beta Cygni is located at the head of the swan, it is sometimes called the "beak star".p. 416, ''In Quest of the Universe'', Theo Koupelis and Karl F. Kuhn, 5th ed., Sudbury, Massachusetts: Jones & Bartlett Publishers, 2007, . With

Deneb Deneb () is a first-magnitude star in the constellation of Cygnus, the swan. Deneb is one of the vertices of the asterism known as the Summer Triangle and the "head" of the Northern Cross. It is the brightest star in Cygnus and the ...

(Sadr),

, and

(Gienah), it forms the asterism called the Northern Cross.

Properties

Beta Cygni is about away from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. When viewed with the naked eye, Albireo appears to be a single star. However, in a

it resolves into a

consisting of β Cygni A (amber,

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

3.1), and β Cygni B (blue-green, apparent magnitude 5.1). Separated by 35 seconds of arc,Entry
The Washington Double Star Catalog
identifier 19307+2758, discoverer identifier STFA 43. Accessed on line July 9, 2008. the two components provide one of the best contrasting double stars in the sky due to their different colors. It is not known whether the two components β Cygni A and B are orbiting around each other in a physical

, or if they are merely an

optical double In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a bi ...

. If they are a physical binary, their orbital period is probably at least 100,000 years.p. 46, ''The Monthly Sky Guide'', Ian Ridpath, Wil Tirion, Cambridge University Press, 2006, . Some experts, however, support the optical double argument, based on observations that suggest different

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

s for the components, which implies that they are unrelated. The primary and secondary also have different measured distances from the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

mission – for the primary and for the secondary. More recently the

Gaia In Greek mythology, Gaia (; from Ancient Greek , a poetical form of , 'land' or 'earth'),, , . also spelled Gaea , is the personification of the Earth and one of the Greek primordial deities. Gaia is the ancestral mother—sometimes parthenog ...

mission has measured distances of about 330–390 light years (100–120 parsecs) for both components, but noise in the astrometric measurements for the stars means that data from Gaia's second data release is not yet sufficient to determine whether the stars are physically associated. In around 3.87 million years, Albireo will become the brightest star in the night sky. – based on computations from

HIPPARCOS ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

data. (The calculations exclude stars whose distance or

is uncertain.) tp://tlgleonid.asuscomm.com/HITACHI/BOOK_ASTRO/S&T/SkyandTelescope_1998%20-%20astronomy/04/199804059063.pdf PDF/ref> It will peak in brightness with an apparent magnitude of –0.53 in 4.61 million years. There are a further 10 faint companions listed in the Washington Double Star catalogue, all fainter than magnitude 10. Only one is closer to the primary than Albireo B, with the others up to 142" away.Entry, WDS identifier 19307+2758
Sixth Catalog of Orbits of Visual Binary Stars
, William I. Hartkopf & Brian D. Mason, U.S. Naval Observatory. Accessed on line July 9, 2008

Albireo A

The

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

of Beta Cygni A was found to be composite when it was observed as part of the

Henry Draper Henry Draper (March 7, 1837 – November 20, 1882) was an American doctor and amateur astronomer. He is best known today as a pioneer of astrophotography. Life and work Henry Draper's father, John William Draper, was an accomplished doctor, ch ...

Memorial project in the late 19th century, leading to the supposition that it was itself double. This was supported by observations from 1898 to 1918 which showed that it had a varying

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

. In 1923, the two components were identified in the Henry Draper Catalogue as HD 183912 and HD 183913. In 1978, speckle interferometry observations using the 1.93m telescope at the

Haute-Provence Observatory The Haute-Provence Observatory (OHP, french: Observatoire de Haute-Provence) is an astronomical observatory in the southeast of France, about 90 km east of Avignon and 100 km north of Marseille. It was established in 1937 as a national ...

resolved a companion at 0.125". This observation was published in 1980, and the companion is referred to as component Ab in the

Washington Double Star Catalog The Washington Double Star Catalog, or WDS, is a catalog of double stars, maintained at the United States Naval Observatory. The catalog contains positions, magnitudes, proper motions and spectral types and has entries for (as of June 2017) 141, ...

. In 1976

speckle interferometry Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("''i ...

was used to resolve a companion using the 2.1-meter telescope at the

Kitt Peak National Observatory The Kitt Peak National Observatory (KPNO) is a United States astronomy, astronomical observatory located on Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono Oʼodham Nation, west-southwest of Tucson, Arizona. With ...

. It was measured at a separation of 0.44", and it is noted that the observation was inconsistent with the Haute-Provence observations and hence not of the same star. Although these observations pre-dated those at Haute-Provence, they were not published until 1982 and this component is designated Ac in the Washington Double Star Catalog. It is designated as component C in the

Catalog of Components of Double and Multiple Stars The Catalog of Components of Double and Multiple Stars, or CCDM, is an astrometric star catalogue of double and multiple stars. It was made by Jean Dommanget and Omer Nys at the Royal Observatory of Belgium in order to provide an input cata ...

, not to be confused with component C in the Washington Double Star Catalog which is a faint optical companion. An orbit for the pair has since been computed using interferometric measurements, but as only approximately a quarter of the orbit has been observed, the orbital parameters must be regarded as preliminary. The period of this orbit is 214 years. The confirmed close pair are referred to as Aa and Ac in modern papers, with Ab being the unconfirmed third component. The diameter of the primary K-type giant star has been measured using

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

. A uniform disk of approximately 4.5 mas was measured at optical and near-

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

wavelengths, and a limb-darkened diameter of 4.834 mas was calculated, equivalent to a radius of at a distance of 133 pc.

Albireo B

β Cygni B is a fast-rotating

Be star Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer e ...

, with an equatorial rotational velocity of at least 250 kilometers per second. Its surface temperature has been spectroscopically estimated to be about 13,200 K. β Cygni B has been reported to be a very close double, but the observations appear to have been incorrect.

Moving group

Analysis of

Gaia Data Release 2 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especia ...

astrometry suggests that four fainter stars may form a

moving group In astronomy, stellar kinematics is the Observational astronomy, observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar Velocity, velocities in the Milky W ...

along with the brighter visible components.

Namesakes

''Albireo'' (AK-90) was a

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

''Crater''-class cargo ship named after the star.

Notes

References

External links

*
A picture of Albireo by Stefan Seip

at Pete Roberts' Fuzzy Blobs site

including more information about the origin of the name Albireo. {{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System B-type main-sequence stars Cygni, Beta Be stars Cygni, 06 Binary stars Cygnus (constellation) BD+27 3410 183912 095947 7417 K-type bright giants

Albireo Albireo 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', ...

Triple stars