Beta Tucanae, Latinized from β Tucanae, is a group of six

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 ...

s which appear to be at least loosely bound into a

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

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 ...

Tucana Tucana (The Toucan) is a constellation in the southern sky, named after the toucan, a South American bird. It is one of twelve constellations conceived in the late sixteenth century by Petrus Plancius from the observations of Pieter Dirkszoon K ...

. Three of the stars are luminous and distinct enough to have been given their own

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

s, β¹ Tucanae through β³ Tucanae. The system is approximately 140

light years 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 Astro ...

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 ...

β^{1, 2} Tucanae

The two brightest stars, Beta¹ Tucanae and Beta² Tucanae, also referred to as Beta Tucanae A (or AB) and Beta Tucanae C (or CD), are 27

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

s, or at least 1100

astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

s (AU) apart. They are both main sequence dwarfs, Beta¹ a blue-white B-type star with an

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), ...

of +4.36, and Beta² a white A-type star with an

of +4.53. Both of these bright stars are binaries. Beta Tucanae B is a magnitude +13.5 star which is a close companion to Beta¹, being 2.4

s, or at least 100 AU away. Beta Tucanae C is a close binary of components Ca and Cb, separated by 0.6 AU. The 6th magnitude Beta Tucanae D, is another A-type star which is separated by approximately 0.38

s (16 AU) from Beta Tucanae C.

Hierarchy of orbits in the β Tucanae system

β³ Tucanae

Beta³ Tucanae is a suspected

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 ...

which is separated from Beta¹ and Beta² Tucanae by 9

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

s on the sky, which puts the two systems at least 23 000

s (AU) or 0.37

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 apart. It is not clear how tightly Beta³ Tucanae is gravitationally bound to the rest of the β Tucanae system, but all the stars have similar distances from Earth and have the same

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

on the sky, indicating they are gravitationally influencing each other to some degree. In 1926, Beta³ Tucanae was reported to be a binary, with two components of magnitudes 5.7 and 6.1 separated by , although more recent observations could not confirm this. At the separation of they would be separated by at least . Beta³ Tucanae has an

infrared excess An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are of ...

, suggesting the presence a

debris disk A debris disk (American English), or debris disc ( Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris ...

around the primary star.

References

{{DEFAULTSORT:Beta Tucanae B-type main-sequence stars A-type main-sequence stars Binary stars 6 Tucana Tucanae, Beta Durchmusterung objects 002884 2885 3003 002484 487 578 0126 36

β1, 2 Tucanae

β3 Tucanae

References

β^{1, 2} Tucanae

β³ Tucanae