Upsilon Orionis (υ Ori, υ Orionis) is a

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 ...

Orion. It has the traditional name ''Thabit'' or ''

Tabit Pi3 Orionis (π3 Orionis, abbreviated Pi3 Ori, π3 Ori), also named Tabit , is a star in the celestial equator, equatorial constellation of Orion (constellation), Orion. At an apparent visual magnitude of 3.16, it is Bortle Dark-Sky Sc ...

'' (ﺛﺎﺑﺖ,

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

for "the endurer"), a name shared with Pi³ Orionis. It is a blue-white

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 ...

star of

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), ...

4.62 located over 1,300 light-years distant from the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. It is a suspected

Beta Cephei variable Beta Cephei variables, also known as Beta Canis Majoris stars, are variable stars that exhibit small rapid variations in their brightness due to pulsations of the stars' surfaces, thought due to the unusual properties of iron at temperatures of 200 ...

Name

Located south of

Iota Orionis Iota Orionis (ι Orionis, abbreviated ι Ori) is a Star system, multiple star system in the celestial equator, equatorial constellation of Orion (constellation), Orion the hunter. It is the eighth-brightest member of Orion with an Appa ...

, Upsilon Orionis is one of two stars (the other is 29 Orionis) marking the top of Orion's right boot in

Johann Bayer Johann Bayer (; 1572 – 7 March 1625) was a German lawyer and uranographer (celestial cartographer). He was born in Rain in 1572. In 1592, aged 20, he began his study of philosophy and law at the University of Ingolstadt, after which he ...

's ''

Uranometria is a star atlas produced by Johann Bayer. It was published in Augsburg in 1603 by Christoph Mang (''Christophorus Mangus'') under the full title (from Latin: ''Uranometria, containing charts of all the constellations, drawn by a new method an ...

'' (1603). It was given the number 36 by

John Flamsteed John Flamsteed (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, ''Catalogus Britannicus'', and a star atlas called '' Atlas ...

, while its proper name appears to be derived from the Arabic ''Al Thabit'' "the endurer". In his '' Star-Names and Their Meanings'' (1899), American amateur naturalist Richard Hinckley Allen noted that the name appeared on the star atlas ''Geography of the Heavens'', composed by Elijah Hinsdale Burritt, but its ultimate origin was unknown.

Properties

Since 1943, this star has been consistently defined as a B0 main sequence star used as a reference for classifying the spectra of other stars on the MK scale, although in other studies it has been classified as O9V and O9.5V. The Galactic O-Star Spectroscopic Survey defined it as the standard star for the O9.7V spectral type in 2011, but the 2016 version redefined it as B0V. In a 1981 paper, Thabit was observed to have nonradial pulsations over a period of around 12 hours, and has been classified as a

slowly pulsating B star A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are main sequence, main-sequence stars of B- ...

. Subsequent review of

Hipparcos catalog ''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 and distances of ...

data indicated it was most likely a

, and is hence considered a candidate for that class. These are blue-white main sequence stars of around 10 to 20 times the mass of the Sun that pulsate with periods of 0.1 to 0.3 days; their changes in magnitude are much more pronounced in the ultraviolet than in the visual spectrum. It is classified as a Beta Cephei variable by the

American Association of Variable Star Observers The American Association of Variable Star Observers (AAVSO) is an international nonprofit organization. Founded in 1911, the organization focuses on coordinating, analyzing, publishing, and archiving variable star observations made largely by ama ...

, and has an

of +4.62. Thabit's

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 ...

has been measured at , yielding a distance of approximately 1,325

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 from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

Spectroscopic Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectrosc ...

observations found it to be 1,260

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

s distant, with a radius 5.5 and a luminosity 32,000 that of the Sun, 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 32,900 K and a mass 17.5 that of the Sun. It is one of the most massive stars of the Orion OB1c association (in Orion's Sword).

Notes

References

{{DEFAULTSORT:Upsilon Orionis Orion (constellation) Orionis, Upsilon Thabit Beta Cephei variables Orionis, 36 025923 O-type main-sequence stars

1855 Events January–March * January 1 – Ottawa, Ontario, is incorporated as a city.' * January 5 – Ramón Castilla begins his third term as President of Peru. * January 23 ** The first bridge over the Mississippi River o ...

036512 Durchmusterung objects B-type main-sequence stars