Kappa Ursae Majoris (κ Ursae Majoris, abbreviated Kappa UMa, κ UMa) is a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

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 ...

Ursa Major Ursa Major, also known as the Great Bear, is a constellation in the Northern Sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear", referring to and contrasting it with nearby Ursa M ...

. With a combined

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 +3.60, the system is approximately 358

light-years 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 Astro ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. The two components are designated Kappa Ursae Majoris A (officially named Alkaphrah , a traditional name of the system) and B.

Nomenclature

''κ Ursae Majoris'' ( Latinised to ''Kappa Ursae Majoris'') 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 ...

. The designations of the two components as ''Kappa Ursae Majoris A'' and ''B'' derives from the convention used by the Washington Multiplicity Catalog (WMC) for

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 ...

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). The traditional name of the system is Alkafzah (corrupted to ''Alkaphrah'' or ''El Koprah''), from the Arabic القفزة ''al-qafzah'' "the leap". (Cf. Alula Borealis and Alula Australis.) 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 catalog 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 ''Alkaphrah'' for the component Kappa Ursae Majoris A on 5 September 2017 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 ''

Three Steps The Three Steps are three prominent rocky steps on the northeast ridge of Mount Everest. They are located at altitudes of , , and . The Second Step is especially significant both historically and in mountaineering terms. Any climber who wants to ...

'', refers to an asterism consisting of Kappa Ursae Majoris,

Iota Ursae Majoris Iota Ursae Majoris (ι Ursae Majoris, abbreviated Iota UMa, ι UMa), also named Talitha , is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of 3.14, making it vi ...

Lambda Ursae Majoris Lambda Ursae Majoris (λ Ursae Majoris, abbreviated Lambda UMa, λ UMa), formally named Tania Borealis , is a star in the northern circumpolar constellation of Ursa Major. Properties This star has an apparent visual magnit ...

, Mu Ursae Majoris,

Nu Ursae Majoris Nu Ursae Majoris (ν Ursae Majoris, abbreviated Nu UMa, ν UMa), formally named Alula Borealis , is a double star in the northern circumpolar constellation of Ursa Major. At an apparent visual magnitude of +3.490, it is br ...

and

Xi Ursae Majoris Xi Ursae Majoris is a quintuple star system away in the constellation of Ursa Major. It has the traditional name Alula Australis; ''Xi Ursae Majoris'' is the Bayer designation, which is Latinised from ξ Ursae Majoris and abbre ...

. 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 Kappa Ursae Majoris itself is (, ).(Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日

Properties

Both components of the binary star are white A-type main sequence dwarfs. They have

s of +4.2 and +4.5. The

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 the binary is 35.6 years (13,007.2 days), and the two stars are separated by 0.18

arcseconds 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 ...

. An

infrared excess An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are of ...

indicates a

debris disk A debris disk (American English), or debris disc ( Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris ...

with a mean temperature of 165 K is orbiting the primary at a separation of .

References

{{Stars of Ursa Major A-type main-sequence stars Circumstellar disks Binary stars Ursa Major Ursae Majoris, Kappa Durchmusterung objects Ursae Majoris, 12 077327 044471 3594 Alkaphrah