Xi Geminorum (ξ Geminorum, abbreviated Xi Gem, ξ Gem), formally named Alzirr , 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

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the Sun path, apparent path of the Sun across the celestial sphere over the course of the year. ...

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 ...

Gemini Gemini may refer to: Space * Gemini (constellation), one of the constellations of the zodiac ** Gemini in Chinese astronomy * Project Gemini, the second U.S. crewed spaceflight program * Gemini Observatory, consisting of telescopes in the Northern ...

. It forms one of the four feet of the outline demarcating the Gemini twins. The star has an

apparent visual 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 lig ...

of 3.35, which is bright enough for it to be seen with the naked eye. From

stellar parallax Stellar parallax is the apparent shift of position of any nearby star (or other object) against the background of distant objects, and a basis for determining (through trigonometry) the distance of the object. Created by the different orbital p ...

measurements, its distance 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 ...

can be estimated as .

Nomenclature

''ξ Geminorum'' ( Latinised to ''Xi Geminorum'') 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 name of ''Al Zirr'' or ''Alzirr'', from the Arabic الزِرّ ''al-zirr'' "the button". 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 approved the name ''Alzirr'' for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names. This star, along with

Gamma Geminorum Gamma Geminorum (γ Geminorum, abbreviated Gamma Gem, γ Gem), formally named Alhena , is the third-brightest object in the constellation of Gemini. It has an apparent visual magnitude of 1.9, making it easily visible to the naked eye ...

(Alhena),

Mu Geminorum Mu Geminorum or μ Geminorum, formally named Tejat (), is a single star in the northern constellation of Gemini. From parallax measurements obtained during the Hipparcos mission, it is roughly distant from the Sun. The position of the st ...

, Nu Geminorum and Eta Geminorum were ''al-hanʽah'' "the brand" (on the neck of the camel). They also were associated in ''al-nuḥātai'', the dual form of ''al-nuḥāt'', "the camel's hump". 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 ''

Well A well is an excavation or structure created in the ground by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The ...

(asterism)'', refers to an asterism consisting of Xi Geminorum, Mu Geminorum, Nu Geminorum, Gamma Geminorum,

Epsilon Geminorum Epsilon Geminorum or ε Geminorum, formally named Mebsuta , is a star in the constellation of Gemini, on the outstretched right 'leg' of the twin Castor. The apparent visual magnitude of +3.06 makes it one of the brighter stars in this ...

36 Geminorum 36 may refer to: * 36 (number), the natural number following 35 and preceding 37 * One of these years of Gregorian or Julian calendars: ** 36 BC, 1st century BCE ** AD 36, 1st century ** 1936, 20th century ** 2036, 21st century Arts and entertai ...

Zeta Geminorum Zeta Geminorum (ζ Geminorum, abbreviated Zeta Gem, ζ Gem) is a bright star with cluster components, distant optical components and a likely spectroscopic partner in the zodiac constellation of Gemini — in its south, on the left 'leg' ...

and

Lambda Geminorum Lambda Geminorum, Latinized from λ Geminorum, is a candidate multiple star system in the constellation Gemini. It is visible to the naked eye at night with a combined apparent visual magnitude of 3.57. The distance to this system is 10 ...

. Consequently, Xi Geminorum itself is known as (, en, the Fourth Star of Well.)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

Although generally considered a single star, there is some evidence that Xi Geminorum may instead be a

spectroscopic binary A binary star is a system of two star, stars that are gravity, 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 separa ...

system consisting of two component stars of equal mass. Xi Geminorum has a

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 F5 IV-V, which is

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

star that is in the process of

evolving Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...

away from the

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 ...

of stars like the Sun. It has about 162% of the

Sun's mass 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 of ...

and is radiating more than 11 times the

luminosity of the Sun The solar luminosity (), is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal s ...

. This energy is being emitted from the outer envelope of the star at 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 6,464 K. This causes the star to take on the yellow-white hue common to F-type stars. X-ray emission has been detected from this star, which has an estimated X-ray luminosity of . It has the spectroscopic signature of a rapidly rotating star, 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 about 66 km s⁻¹.

References

External links

* {{DEFAULTSORT:Xi Geminorum F-type subgiants Gemini (constellation) Geminorum, Xi Alzirr 0242 Geminorum, 31 032362 2484 048737 Durchmusterung objects