Alpha Ceti (α Ceti, abbreviated Alpha Cet, α Cet), officially named Menkar , is the second-brightest

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

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 ...

Cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water- ...

. It is a cool luminous

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...

estimated to be about 250

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s away based on

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

Nomenclature

''Alpha Ceti'' is the star'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 ...

. It has the traditional name Menkar, deriving from the Arabic word منخر ''manħar'' "nostril" (of Cetus). In 2016, 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 ...

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 ''Menkar'' for this star. This star, along with γ Cet (Kaffaljidhma), δ Cet, λ Cet (also Menkar), μ Cet, ξ¹ Cet and ξ² Cet were ''Al Kaff al Jidhmah'', "the Part of a Hand". 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 '' Circular Celestial Granary'', refers to an asterism consisting of α Ceti, κ¹ Ceti,

λ Ceti Lambda Ceti, Latinized from λ Ceti, is a B-type star of fifth-magnitude located in the constellation Cetus. Historically, the star bore the traditional name Menkar, although today that name is more commonly associated with α Ceti. Th ...

, μ Ceti, ξ¹ Ceti, ξ² Ceti,

ν Ceti ν Ceti, Latinized as Nu Ceti, is a binary star system in the equatorial constellation of Cetus. It is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.86. The system is located approxim ...

γ Ceti Gamma Ceti (γ Ceti, abbreviated Gamma Cet, γ Cet) is a triple star system in the equatorial constellation of Cetus. It has a combined apparent visual magnitude of 3.47. Based upon parallax measurements, this star is located at a distanc ...

δ Ceti Delta Ceti, Latinized from δ Ceti, is a single, blue-white hued star in the equatorial constellation of Cetus. The star's apparent visual magnitude of +4.06 means it is near to the cusp of the faintest third of the stars that are visibl ...

75 Ceti 75 Ceti is a star in the equatorial constellation of Cetus with at least two planets. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of +5.36. The star is located distant from the Sun, based ...

70 Ceti This is the list of notable stars in the constellation Cetus, sorted by decreasing brightness. See also * List of stars by constellation References * * * * * * * {{Stars of Cetus *List Cetus Cetus () is a constellation, somet ...

63 Ceti 63 Ceti is a star in the constellation of Cetus, located just over a degree south of the celestial equator. With an apparent magnitude of about 5.9, the star is barely visible to the naked eye (see Bortle scale) as a dim, orange-hued point ...

and

66 Ceti This is the list of notable stars in the constellation Cetus, sorted by decreasing brightness. See also * List of stars by constellation References * * * * * * * {{Stars of Cetus *List Cetus Cetus () is a constellation, somet ...

. 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 α Ceti itself is (, .)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日

Characteristics

Despite having the Bayer designation α Ceti, at visual magnitude 2.54 this star is actually not the brightest star in the constellation Cetus. That honor goes instead to

Beta Ceti Beta Ceti (β Ceti, abbreviated Beta Cet, β Cet), officially named Diphda , is the brightest star in the constellation of Cetus. Although designated 'beta', it is actually brighter than the 'alpha' star in the constellation, Menkar, by ...

at magnitude 2.04. Menkar is a

with 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 gratin ...

of M1.5 IIIa. It has more than twice the

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

and, as a

giant star A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsp ...

, has expanded to about 100 times the

Sun's radius Solar radius is a unit of distance used to express the size of objects in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: 1\,R_ = 6.957\ti ...

. The large area of the

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

means that it is emitting about 1,765 times as much energy as the Sun, even though the

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 ...

is only (compared to on the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

). The relatively low temperature gives Menkar the red hue of an M-type star. Menkar has evolved from the

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

after exhausting the hydrogen at its core. It has also exhausted its core helium, becoming an asymptotic giant branch star, and will probably become a highly unstable star like

Mira Mira (), designation Omicron Ceti (ο Ceti, abbreviated Omicron Cet, ο Cet), is a red-giant star estimated to be 200–300 light-years from the Sun in the constellation Cetus. ο Ceti is a binary stellar system, consisting of a vari ...

before finally shedding its outer layers and forming a

planetary nebula A planetary nebula is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to planets. The ...

, leaving a relatively large

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

remnant. It has been observed to periodically vary in brightness, but only with an amplitude of about one hundredth of a magnitude.

Namesakes

''Menkar'' (AK-123) was a

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

Crater class cargo ship The ''Crater''-class cargo ship were converted EC2-S-C1 type, Liberty cargo ships, constructed by the United States Maritime Commission (USMC) for use by the US Navy during World War II. The designation 'EC2-S-C1': 'EC' for Emergency Cargo, '2' ...

named after the star.

References

External links

Assorted figures related to Alpha Ceti
{{DEFAULTSORT:Alpha Ceti M-type giants Asymptotic-giant-branch stars Cetus Ceti, Alpha BD+03 0419 Ceti, 92 018884 014135 0911 Menkar