Epsilon Scorpii (ε Scorpii, abbreviated Eps Sco, ε Sco), formally named Larawag , 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 southern

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 ...

Scorpius Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the Gre ...

. It 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 +2.3, making it the fifth-brightest member of the constellation.

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 made during 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 ...

mission provide an estimated distance to this star 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 ...

. Epsilon Scorpii 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 K1 III, which indicates it has exhausted the supply of hydrogen at its core and

evolved 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 ...

into a

giant star A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moo ...

. The

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

-measured

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, after correcting for

limb darkening Limb darkening is an optical effect seen in stars (including the Sun), where the central part of the disk appears brighter than the edge, or ''limb''. Its understanding offered early solar astronomers an opportunity to construct models with such ...

, is , which, at its estimated distance, equates to a physical radius of nearly 13 times the

radius of the Sun Solar radius is a unit of distance used to express the size of stars 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\t ...

. Presently it is generating energy through the

nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifest ...

of helium at its core, which, considering the star's composition, places it along an evolutionary branch termed the

red clump Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...

. The star's outer atmosphere has 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 4,560 K, giving it the orange hue of a cool

K-type star In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

. ε Scorpii is classified as a suspected

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

, although a study of

photometry showed a variation of no more than 0.01–0.02 magnitudes. It is an X-ray source with a luminosity of .

Nomenclature

''ε Scorpii'' ( Latinised to ''Epsilon Scorpii'') 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. ...

. The star bore the traditional name ''Larawag'' in the culture of the

Wardaman people The Wardaman people are a small group of Aboriginal Australians living about South-West of Katherine, on Menngen Aboriginal Land Trust in the Northern Territory of Australia. Language Wardaman is a non Pama-Nyungan language. Though close to ...

of the

Northern territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, meaning ''clear sighting''. 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 ''Larawag'' for Epsilon Scorpii on 19 November 2017 and it is now so included in the List of IAU-approved Star Names.

Patrick Moore Sir Patrick Alfred Caldwell-Moore (; 4 March 1923 – 9 December 2012) was an English amateur astronomer who attained prominence in that field as a writer, researcher, radio commentator and television presenter. Moore was president of the Brit ...

introduced the name ''Wei'' as

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 this star. However, this seems to be a misreading, as

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 ...

(, English ''

Tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...

'') refers to an asterism (i.e.

Chinese constellation Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" (Chinese ''xīng guān''). The Chinese asterisms are generally smaller than the constellations of Hellenistic t ...

) consisting of Epsilon Scorpii,

Mu¹ Scorpii Mu1 Scorpii (μ1 Scorpii, abbreviated Mu1 Sco, μ1 Sco) is a binary star system in the southern zodiac constellation of Scorpius. The combined apparent visual magnitude of the pair is about magnitude 3, making it one of the brighter m ...

, Zeta¹ Scorpii and Zeta² Scorpii,

Eta Scorpii Eta Scorpii, Latinized from η Scorpii, is a star in the southern zodiac constellation of Scorpius. With an apparent visual magnitude of 3.33, this is one of the brighter members of the Scorpius and is the furthest south of the constel ...

Theta Scorpii Theta Scorpii (θ Scorpii, abbreviated Theta Sco, θ Sco) is a binary star in the southern zodiac constellation of Scorpius. The apparent visual magnitude of this star is +1.87, making it readily visible to the naked eye and one of the ...

, Iota² Scorpii and Iota¹ Scorpii,

Kappa Scorpii Kappa Scorpii, Latinized from κ Scorpii, is a binary star system in the southern constellation of Scorpius. With an apparent visual magnitude of 2.4, this star system is readily visible to the naked eye. Parallax measurements place ...

Lambda Scorpii Lambda Scorpii is a triple star system and the second-brightest object in the constellation of Scorpius. It is formally named Shaula; ''Lambda Scorpii'' is its Bayer designation, which is Latinised from λ Scorpii and abbreviated Lamb ...

and Upsilon Scorpii. Consequently, the name for Epsilon Scorpii itself is (), which means "the Second Star of Tail".

In culture

Epsilon Scorpii appears on the

flag of Brazil The national flag of Brazil ( pt, bandeira do Brasil), is a blue disc depicting a starry sky (which includes the Southern Cross) spanned by a curved band inscribed with the national motto "''Ordem e Progresso''" ("Order and Progress"), within a y ...

, symbolising the state of

Ceará Ceará (, pronounced locally as or ) is one of the 26 states of Brazil, located in the northeastern part of the country, on the Atlantic coast. It is the eighth-largest Brazilian State by population and the 17th by area. It is also one of the ...

References

{{Stars of Scorpius K-type giants Horizontal-branch stars Suspected variables Scorpius (constellation) Larawag Scorpii, Epsilon Durchmusterung objects Scorpii, 26 Gliese and GJ objects 151680 082396 6241