Tau Orionis (τ Ori, τ Orionis) is a

binary star A binary star or binary star system 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 as separate stars us ...

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 ...

Orion. If an imaginary line is drawn north-west between the stars

Rigel Rigel is a blue supergiant star in the constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori. Rigel is the brightest and most massive componentand ...

and

Mintaka Mintaka , designation Delta Orionis (δ Orionis, abbreviated Delta Ori, δ Ori) and 34 Orionis (34 Ori), is a quintuple star system some 1,200 light-years from the Sun in the constellation of Orion. Together with Alnitak (Zeta ...

, Tau Orionis can be found roughly one-sixth of the way to Mintaka. It is visible to the naked eye with a combined

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...

of 3.58. Based upon an annual parallax shift of 6.6 mas, it is located around 490

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 distant. This is a

spectroscopic binary A binary star or binary star system 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 as separate stars us ...

system with 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 90 days and a very high

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.834. It is a

heartbeat star Heartbeat stars are pulsating variable binary star systems in eccentric orbits with vibrations caused by tidal forces. The name "heartbeat" comes from the similarity of the light curve of the star with what a heartbeat looks like through an elec ...

, showing variations on its

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

during to the close

periastron An apsis (; ) is the farthest or nearest point in the orbit of a planetary-mass object, planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two maximum a ...

passage. The components have masses of and a combined

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 B5 III. The star has a

peculiar velocity Peculiar motion or peculiar velocity refers to the velocity of an object relative to a ''rest frame''—usually a frame in which the average velocity of some objects is zero. Galactic astronomy In galactic astronomy, peculiar motion refers to t ...

through space of 16.9 km/s. Tau Orionis has three visual companions: magnitude 11.0 component B at an

angular separation Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When t ...

of 33.30″ along a position angle of 251°; magnitude 10.9 component C lying some 3.80″ from component B; and magnitude 10.9 component D at 36.0″ from τ Ori along a position angle of 51°, all as of 2011.

Proper names

According to Richard H. Allen, this star, along with β Eri, λ Eri and ψ Eri were Al Kursiyy al Jauzah, "the Chair (or "Footstool") of the Central One". However, per the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Al Kursiyy al Jauzah'' were the title for just three stars: β Eri as ''Cursa'', ψ Eri as ''Al Kursiyy al Jauzah I'' and λ Eri as ''Al Kursiyy al Jauzah II'', excluding this star. In Chinese, (), meaning '' Jade Well'', refers to an asterism consisting of τ Orionis, β Eridani, λ Eridani and ψ Eridani. 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 τ Orionis itself is (, .).AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 15 日
From this Chinese title, the name Yuh Tsing is derived.

References

External links

* {{DEFAULTSORT:Tau Orionis Suspected variables B-type giants Orion (constellation) Orionis, Tau Durchmusterung objects Orionis, 20 024674 034503

1735 Events January–March * January 2 – Alexander Pope's poem '' Epistle to Dr Arbuthnot'' is published in London. * January 8 – George Frideric Handel's opera '' Ariodante'' is premièred at the Royal Opera House in Covent ...