Gamma Ursae Majoris (γ Ursae Majoris, abbreviated Gamma UMa, γ UMa), formally named Phecda , is a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

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 ...

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 ...

. Since 1943, 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 this star has served as one of the stable anchor points by which other stars are classified. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measurements with 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 ...

'' astrometry satellite, it is located at distance of around 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 ...

. It is more familiar to most observers in the

northern hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

as the lower-left star forming the bowl of the

Big Dipper The Big Dipper ( US, Canada) or the Plough ( UK, Ireland) is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude. Four define a "bowl" ...

, together with Alpha Ursae Majoris (Dubhe, upper-right),

Beta Ursae Majoris Beta Ursae Majoris (β Ursae Majoris, abbreviated Beta UMa, β UMa), formally named Merak , is a star in the northern constellation of Ursa Major. The apparent visual magnitude of this star is +2.37, which means it is read ...

(Merak, lower-right) and

Delta Ursae Majoris Delta Ursae Majoris (δ Ursae Majoris, abbreviated Delta UMa, δ UMa), formally named Megrez , is a star in the northern constellation of Ursa Major. With an apparent magnitude of +3.3, it is the dimmest of the seven stars ...

(Megrez, upper-left). Along with four other stars in this well-known asterism, Phecda forms a loose association of stars known as the Ursa Major moving group. Like the other stars in the group, it is a

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

star, as the Sun is, although somewhat hotter, brighter and larger. Phecda is located in relatively close physical proximity to the prominent Mizar–Alcor star system. The two are separated by an estimated distance of ; much closer than the two are from the Sun. The star

is separated from Gamma Ursae Majoris by .

Nomenclature

''γ Ursae Majoris'' ( Latinised to ''Gamma Ursae Majoris'') is the star'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. ...

. It bore the traditional names ''Phecda'' or ''Phad'', derived from the

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 ...

phrase ''fakhth al-dubb'' ('thigh of the bear'). In 2016, 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 ...

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 ''Phecda'' for this star. To the

Hindu Hindus (; ) are people who religiously adhere to Hinduism.Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...

s this star was known as ''

Pulastya Pulastya (Sanskrit: पुलस्त्य) is one of the ten Prajapati, and one of the mind-born sons of Brahma in Hinduism. He is also one of the Saptarishi (Seven great sages) in the first age of Manu, the Manvantara.

'', one of the

seven rishis The Saptarishi () are the seven rishis of ancient India who are extolled in the Vedas, and other Hindu literature. The Vedic Samhitas never enumerate these rishis by name, although later Vedic texts such as the Brahmanas and Upanisads do so. ...

. 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 '' Northern Dipper'', refers to an asterism equivalent to the Big Dipper. 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 often a ...

for Gamma Ursae Majoris itself is (, en, the Third Star of Northern Dipper) and (, en, Star of Celestial Shining Pearl).AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日
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Properties

Gamma Ursae Majoris is an

Ae star A Herbig Ae/Be star (HAeBe) is a pre-main-sequence star – a young () star of spectral types A or B. These stars are still embedded in gas-dust envelopes and are sometimes accompanied by circumstellar disks. Hydrogen and calcium emission lines a ...

, which is surrounded by an envelope of gas that is adding

emission line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s to the

of the star; hence the 'e' suffix in the

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of A0 Ve. It has 2.6 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

, three times the Sun's radius, and an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of in its outer atmosphere. This star is rotating rapidly, with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of . The estimated

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...

of this star is about 0.92 mas. It has an estimated age of 300 million years. Gamma Ursae Majoris is also an

astrometric binary A binary star 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 using a telescope as separate stars, in wh ...

: the companion star regularly perturbs the Ae-type primary star, causing the primary to wobble around the

barycenter In astronomy, the barycenter (or barycentre; ) is the center of mass of two or more bodies that orbit one another and is the point about which the bodies orbit. A barycenter is a dynamical point, not a physical object. It is an important conc ...

. From this, 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 20.5 years has been calculated. The secondary star is a

K-type main-sequence star A K-type main-sequence star, also referred to as a K-type dwarf or an orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence star ...

that is 0.79 times as massive as the Sun, and with a surface temperature of .

References

{{Stars of Ursa Major A-type main-sequence stars Ursa Major Moving Group

Phecda Gamma Ursae Majoris (γ Ursae Majoris, abbreviated Gamma UMa, γ UMa), formally named Phecda , is a star in the constellation of Ursa Major. Since 1943, the spectrum of this star has served as one of the stable anchor poi ...

Ursae Majoris, Gamma Big Dipper Ursa Major (constellation) Durchmusterung objects Ursae Majoris, 64 103287 058001 4554 Astrometric binaries