Tau Scorpii, Latinized from τ Scorpii, formally known as Paikauhale , 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 ...

. The

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 Tau Scorpii is +2.8, while

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 yield a distance estimate of roughly 470 light-years (150

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, an ...

s) 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 ...

Description

Compared to 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 ...

, Tau Scorpii is a massive

OB star OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB associations. They are short lived, and thus do not move very far from where they formed within their life. During their lifet ...

with 15 times 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 more than six 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 ...

. It is radiating about 20,400 times the

Sun's luminosity 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 ...

from its outer envelope 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 31,440 K. This gives it the blue-white hue characteristic of

B-type stars B type or Type B may refer to: Astronomy * B-type asteroid, a type of relatively uncommon type of carbonaceous asteroid * B-type giant, a type of blue giant star * B-type star, a type of star Biology * B type blood, a type in the ABO blood grou ...

. As yet there is no evidence of a companion in orbit around τ Sco. It is a

magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...

star whose surface magnetic field was mapped by means of Zeeman–Doppler imaging. Tau Scorpii is rotating relatively slowly with a period of 41 days. 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 shows triply ionized oxygen (O IV) that is being generated by X-rays and the

Auger Auger may refer to: Engineering * Wood auger, a drill for making holes in wood (or in the ground) ** Auger bit, a drill bit * Auger conveyor, a device for moving material by means of a rotating helical flighting * Auger (platform), the world's f ...

ionization effect. Observations with the

ROSAT ROSAT (short for Röntgensatellit; in German X-rays are called Röntgenstrahlen, in honour of Wilhelm Röntgen) was a German Aerospace Center-led satellite X-ray telescope, with instruments built by West Germany, the United Kingdom and the Uni ...

space telescope showed it has a higher energy (harder) X-ray spectrum than is usual for B0 V stars. Over the energy range 0.8–1.2 keV, its X-ray luminosity is ''L''_x = with a large ''L''_x to ''L''_bol of log ''L''_x/''L''_bol = –6.53 from

ASCA ''Asca'' is a genus of mites with worldwide distribution in the family Ascidae Ascidae is a family of mites in the order Mesostigmata. Description Ascidae are mites characterised by: seta ''st4'' usually on unsclerotised cuticle, peritrem ...

measurements.

measurements showed a log ''L''_x/''L''_bol ≃ –5.93 for the range 0.1–2.4 keV. The hard component of the X-ray spectrum from τ Sco as studied with

XMM-Newton ''XMM-Newton'', also known as the High Throughput X-ray Spectroscopy Mission and the X-ray Multi-Mirror Mission, is an X-ray space observatory launched by the European Space Agency in December 1999 on an Ariane 5 rocket. It is the second cornerst ...

supports the presence of in-falling clumps of plasma in τ Sco. This star is a

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

member of the Upper Scorpius subgroup of the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs) A more recent analysis of the

HR diagram HR, Hr or hr may refer to: Arts and media Film and television * ''H.R. Pufnstuf'', a children's television series from 1969 * ''HR'', a 2013 television drama starring Alicia Silverstone * HR, a criminal organisation in the American TV series ''Pe ...

position for Tau Scorpii estimates its

to be with a

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

of , consistent with an isochronal age of 5 million years and an estimated mass of 14.5–14.7

solar 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 ...

es.

Nomenclature

''τ Scorpii'' ( Latinised to ''Tau Scorpii'') is the star's Bayer designation. Tau Scorpii and

Sigma Scorpii Sigma Scorpii (or σ Scorpii, abbreviated Sigma Sco or σ Sco), is a multiple star system in the constellation of Scorpius, located near the red supergiant Antares, which outshines it. This system has a combined apparent visual magnitud ...

together bore the traditional name ''Al Niyat'' (or ''Alniyat'') 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 ...

النياط ''al-niyāţ'' "the arteries" and referring to their position flanking the star

Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by σ Scorpii and τ S ...

, the scorpion's heart, with Tau Scorpii being the star to the south. ''Paikauhale'' is the Hawaiian name for Tau Scorpii. In the Hawaiian dictionary by Pukuʻi & Elbert (1986), the word ''paikauhale'' is defined as ''to go gadding about from house to house''. In another Hawaiian dictionary (H.W. Kent, 1993, "Treasury of Hawaiian Words in One Hundred and One Categories", p.367), ''paikauhale'' is defined as ''Vagabond owning no home; house-to-house wanderer.'' 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 ''Paikauhale'' for the star A on 10 August 2018 and it is now so included in the List of IAU-approved Star Names. The name ''Alniyat'' was given to Sigma Scorpii.

Cultural signification

The indigenous Boorong people of northwestern Victoria saw this star (together with σ Sco) as wives of '' Djuit'' (

). 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 ''

Heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

'', refers to an asterism consisting of τ Scorpii, σ Scorpii and

. 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 τ Scorpii itself is (), "the Third Star of Heart".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.

References

{{Stars of Scorpius B-type main-sequence stars Astronomical X-ray sources Upper Scorpius Scorpius (constellation) Scorpii, Tau Durchmusterung objects Scorpii, 23 149438 081266 6165 Paikauhale