TW Piscis Austrini
TW Piscis Austrini is a dwarf star in the constellation Piscis Austrinus. It lies relatively close to the Sun, at an estimated distance of 24.9 light years.
To an observer on Earth the star is visually separated from its larger companion Fomalhaut A by 2 degrees - the width of four full moons.
The TW in the name is astronomical nomenclature for a variable star. This is a flare star of the type known as a BY Draconis variable. It varies slightly in apparent magnitude, ranging from 6.44 to 6.49 over a 10.3 day period. While smaller than the Sun, it is relatively large for a flare star. Most flare stars are red M-type dwarfs.
TW Piscis Austrini lies within a light year of Fomalhaut A. Due to sharing the same proper motion, and the same estimated age of approximately 440±40 million years, astronomers now consider them to be elements of a multiple star system. 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.
In 2019 NASA's Transiting Exoplanet Survey Satellite space telescope found an exoplanet candidate around Fomalhaut B.
