Kappa Ursae Majoris (κ Ursae Majoris, abbreviated Kappa UMa, κ UMa) is a binary star in the constellation of

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 ...

. With a combined

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 ...

of +3.60, the system is approximately 358

light-years 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 ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. 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. 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 systems, and adopted by 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 ...

(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 can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...

, (), meaning ''

Three Steps 3 is a number, numeral, and glyph. 3, three, or III may also refer to: * AD 3, the third year of the AD era * 3 BC, the third year before the AD era * March, the third month Books * '' Three of Them'' (Russian: ', literally, "three"), a 1901 ...

'', 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 v ...

, Lambda Ursae Majoris,

Mu Ursae Majoris Mu Ursae Majoris (μ Ursae Majoris, abbreviated Mu UMa, μ UMa), formally named Tania Australis , is a binary star in the constellation of Ursa Major. An apparent visual magnitude of +3.06 places it among the brighter m ...

, Nu Ursae Majoris and

Xi Ursae Majoris Xi Ursae Majoris is a star system 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 abbreviated Xi U ...

. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are ofte ...

for Kappa Ursae Majoris itself is (, en, Star of Second Upper Step).(Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日
/ref>

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 (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 ...

. 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 oft ...

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 di ...

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 (constellation) Ursae Majoris, Kappa Durchmusterung objects Ursae Majoris, 12 077327 044471 3594 Alkaphrah