Beta Capricorni (β Capricorni, abbreviated Beta Cap, β Cap) is a

multiple star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally called a ''st ...

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 first constellati ...

Capricornus Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat Horn (anatomy), horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is hal ...

and located 328

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s from the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

. Because it is near the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

, Beta Capricorni can be

occulted An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

by the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

, and also (rarely) by

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

s. The system is believed to consist of five stars. With

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

or a small

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

, Beta Capricorni can be resolved into a binary pair. The brighter of the two is designated Beta¹ Capricorni or Beta Capricorni A; the dimmer, Beta² Capricorni or Beta Capricorni B. Both are themselves made up of multiple stars. Beta¹ Capricorni has three components; a single star designated Beta Capricorni Aa (formally named Dabih , the traditional name of the system) and a binary pair, Beta Capricorni Ab (whose two components are designated Beta Capricorni Ab1 and Ab2). Beta² Capricorni is also a binary pair, with components designated Beta Capricorni Ba and Bb. Two other nearby stars were discovered by

John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor and experimental photographer who invented the blueprint and did botanical work. ...

. Sometimes referred to as Beta Capricorni D and E, it is unclear whether they are simply optical doubles or part of the Beta Capricorni system.

Nomenclature

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

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

; ''β¹'' and ''β² Capricorni'' those of its two constituents. The designations of the two constituents as ''Beta Capricorni A'' and ''B'', and those of the sub-components - ''Beta Capricorni Aa'', ''Ab'', ''Ab1'', ''Ab2'', ''Ba'' and ''Bb'' - derive from the convention used by the Washington Multiplicity Catalog (WMC) for

s, and adopted by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(IAU). ''Beta Capricorni'' bore the traditional name ''Dabih'', deriving from the

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

الذابح ''al-dhābiḥ'' "the butcher", with ''Beta¹'' and ''Beta²'' subsequently named ''Dabih Major'' and ''Dabih Minor'', respectively. In 2016, the IAU 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 catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ''Dabih'' for the component ''Beta Capricorni Aa'' on 21 August 2016 and it is now so included in the List of IAU-approved Star Names. In

Chinese Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...

, (), meaning '' Ox (asterism)'', refers to an asterism consisting of Beta Capricorni, Alpha² Capricorni, Xi² Capricorni,

Pi Capricorni Pi Capricorni, Latinized from π Capricorni, is a triple star system in the southern constellation of Capricornus. It has the traditional star name Oculus (meaning ''eye'' in Latin). This system appears blue-white in hue and is visible t ...

Omicron Capricorni Omicron Capricorni (ο Capricorni) is a wide binary star system in the constellation Capricornus. The brighter component has an apparent visual magnitude of +5.94, which is near the lower limit on stellar brightness that still can be seen ...

and

Rho Capricorni Rho Capricorni (ρ Cap, ρ Capricorni) is a binary star in the constellation Capricornus. Sometimes, this star is called by the name Bos, meaning ''the cow'' in Latin. In Chinese, (), meaning '' Ox (asterism)'', refers to an asterism cons ...

. Consequently, the

Chinese name Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethni ...

for Beta Capricorni itself is (, ).香港太空館 - 研究資源 - 亮星中英對照表
, Hong Kong Space Museum. Accessed on line November 23, 2010.

Properties

Beta¹ Capricorni is the brighter of the two components with an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of +3.05, while the dimmer Beta² Capricorni has an apparent magnitude of +6.09. The two components are separated by 3.5

arcminute A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

s on the sky, putting them at least 21,000 AU (0.34

s) apart. They take approximately 700,000 years to complete one

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

Hierarchy of orbits in the β Capricorni system

Beta¹ Capricorni

Beta¹ Capricorni is the more complex of the pair and has a

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

that is difficult to interpret. Its dominant pair of stars are the orange K-type

bright giant A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzspr ...

Beta Capricorni Aa, with an apparent magnitude of +3.08, and the blue-white B-Type main sequence dwarf Beta Capricorni Ab1 with an apparent magnitude of +7.20. They are separated by 0.05

arcsecond A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

s (5 AU) and have an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 3.77 years. The Aa component has a surface temperature of 4900 kelvins, a radius 35 times that of the Sun, and a

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

600 times that of the Sun. The Ab1 component's unseen companion, Beta Capricorni Ab2, orbits Ab1 with an

of 8.7 days. Beta¹ Capricorni is 4.6 degrees north of the ecliptic, so it can be occulted by the Moon.

Beta² Capricorni

Beta² Capricorni is simpler and more studied. Its brighter component, Beta Capricorni Ba, has a magnitude of 6.1 and is an A0-

giant In folklore, giants (from Ancient Greek: ''wiktionary:gigas, gigas'', cognate wiktionary:giga-, giga-) are beings of humanoid appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''gia ...

with 40 times the luminosity of the Sun. The companion, Beta Capricorni Bb, is approximately 3

s from Ba. Ba is unusual for having large amounts of mercury and

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

in its atmosphere.

Beta Capricorni D and E

These lie 112

s away from Beta¹ Capricorni.

References

{{DEFAULTSORT:Beta Capricorni Capricorni, Beta B-type main-sequence stars Capricornus Double stars K-type bright giants 5 A-type giants Dabih Capricorni, 09 100325 45 Durchmusterung objects 193452 7775