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. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speaki ...

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 Capricornus and located 328

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Sun. Because it is near the ecliptic, 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 ...

by the Moon, and also (rarely) by planets. 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, 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, experimental photographer who invented the blueprint and did botanical wor ...

. 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 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. ...

; ''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 (IAU). ''Beta Capricorni'' bore the traditional name ''Dabih'', deriving from the Arabic 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 (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, (), meaning '' Ox (asterism)'', refers to an asterism consisting of Beta Capricorni, Alpha² Capricorni, Xi² Capricorni, Pi Capricorni, Omicron Capricorni and Rho Capricorni. Consequently, the Chinese name for Beta Capricorni itself is (, en, the First Star of Ox).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 of +3.05, while the dimmer Beta² Capricorni has an apparent magnitude of +6.09. The two components are separated by 3.5 arcminutes on the sky, putting them at least 21,000 AU (0.34

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

Hierarchy of orbits in the β Capricorni system

Beta¹ Capricorni

Beta¹ Capricorni is the more complex of the pair and has a spectrum that is difficult to interpret. Its dominant pair of stars are the orange K-type bright giant 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 (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

s (5 AU) and have an orbital period 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 power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

600 times that of the Sun. The Ab1 component's unseen companion, Beta Capricorni Ab2, orbits Ab1 with an orbital period 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 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 Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

and manganese 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 (constellation) Double stars K-type bright giants 5 A-type giants Dabih Capricorni, 09 100325 45 Durchmusterung objects 193452 7775