TW Piscis Austrini (also known as Fomalhaut B) is a

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 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 ...

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 as ...

. It lies relatively close to the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, at an estimated distance of . To an observer on Earth the star is visually separated from its larger companion

Fomalhaut Fomalhaut (, ) is the brightest star in the southern constellation of Piscis Austrinus, the Southern Fish, and one of the brightest stars in the night sky. It has the Bayer designation Alpha Piscis Austrini, which is an alternative ...

(A) by 2 degrees—the width of four full moons. TWPsALightCurve

The name TW Piscis Austrini is a

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

. This is a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

of the type known as a

BY Draconis variable BY Draconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in thei ...

, with surface brightness variations causing the changes as the star rotates. It varies slightly in

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), ...

, ranging from 6.44 to 6.51 over a 10.3-day period. TW Piscis Austrini lies within a light-year of Fomalhaut. Due to sharing 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 ...

, and the same estimated age of approximately 440 ± 40 million years, astronomers now consider them to be elements of a multiple

star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...

. A third star, dimmer and more widely separated, Fomalhaut C, gives the system the widest visual separation, to observers from Earth, at approximately 6 degrees.

Planetary system

In 2019, an

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

candidate around Fomalhaut B was detected by

astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, th ...

, but this remains unconfirmed.

References

External links

TW Piscis Austrini
at SolStation. {{DEFAULTSORT:TW Piscis Austrini Piscis Austrinus K-type main-sequence stars BY Draconis variables Piscis Austrini, TW 216803 113283

8721 87 may refer to: * 87 (number) * one of the years 87 BC, AD 87, 1987, 2087 * Atomic number 87, francium * Intel 8087, a floating-point coprocessor * 87; Common gasoline rating * 87 Sylvia, a large asteroid * Tatra 87, a luxury car See also * * Li ...

0879 CD-32 17321 Fomalhaut