Theta Piscis Austrini, Latinized as θ Piscis Austrini, is a

binary star A binary star 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 using a telescope as separate stars, in ...

system in the southern constellation of

Piscis Austrinus Piscis Austrinus is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish", in contrast with the larger constellation Pisces, which represents a pair of fish. Before the 20th century, it was also known a ...

. It is faintly visible to the naked eye with a combined

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 +5.01. Based upon an annual

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 object ...

shift of 10.16

mas Mas, Más or MAS may refer to: Film and TV * Más y Menos, fictional superhero characters, from the Teen Titans animated television series * "Más" (''Breaking Bad''), a season three episode of ''Breaking Bad'' Songs * ''Más'' (album), by Span ...

as seen from the Earth, the system is located around 320

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s 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 rad ...

. The system is drifting further away with a

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the rate of change of the distance or range between the two points. It is equivalent to the vector projection ...

of +13 km/s. The binary nature of this system was discovered in 1951 by South African astronomer W. S. Finsen. Both components A and B have the same apparent magnitude. They orbit each other with a

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of 20 years and an

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- center, in geometry * Eccentricity (graph theory) of a ...

of 0.256. The pair are

A-type main sequence star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

s with

stellar classification 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 t ...

s of A1 V. A magnitude 11.3 visual companion star, labelled component C, is located at an

angular separation Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

of 33.2

arc second A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The nau ...

s along a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the ...

of 342°, as of 1999. Theta Piscis Austrini is moving through the Galaxy at a speed of 21.3 km/s relative to the Sun. Its projected Galactic orbit carries it between and from the center of the Galaxy. Theta Piscis Austrini came closest to the Sun 2.7 million years ago at a distance of .

Naming

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 v ...

, (), meaning '' Celestial Money'', refers to an asterism consisting of refers to an asterism consisting of θ Piscis Austrini,

13 Piscis Austrini This is the list of notable stars in the constellation Piscis Austrinus, sorted by decreasing brightness. See also * List of stars by constellation References * * * * * {{Stars of Piscis Austrinus *List Piscis Austrinus Piscis Austrinus ...

, ι Piscis Austrini, μ Piscis Austrini and τ Piscis Austrini. 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 oft ...

for θ Piscis Austrini itself is (, en, the Second Star of Celestial Money.)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 5 日
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References

{{DEFAULTSORT:Theta Piscis Austrini A-type main-sequence stars Double stars Piscis Austrinus Piscis Austrini, Theta Durchmusterung objects Piscis Austrini, 10 207155 107608 8326 Binary stars