Other objects contained within the boundaries of the constellation include Lacaille 9352, one of the brightest red dwarf stars in the night sky (though still too faint to see with the naked eye); and PKS 2155-304, a BL Lacertae object that is one of the optically brightest blazars in the sky.

[2][3] Professor of astronomy Bradley Schaefer has proposed that ancient observers must have been able to see as far south as Mu Piscis Austrini to define a pattern that looked like a fish.

[4] Like many of Schaefer's proposals this is nothing new: mu PsA is explicitly mentioned in the Almagest and the constellation is definitely a takeover from ancient Babylon.

[5] Along with the eagle Aquila the crow Corvus and water snake Hydra, Piscis Austrinus was introduced to the Ancient Greeks around 500 BCE; the constellations marked the summer and winter solstices, respectively.

[7] In the 5th century BC, Greek historian Ctesias wrote that the fish was said to have lived in a lake near Bambyce in Syria and had saved Derceto, daughter of Aphrodite, and for this deed was placed in the heavens.

[8] Piscis Austrinus is a constellation bordered by Capricornus to the northwest, Microscopium to the southwest, Grus to the south, Sculptor to the east, and Aquarius to the north.

[11] The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of four segments (illustrated in infobox).

[13][a] Ancient astronomers counted twelve stars as belonging to Piscis Austrinus, though one was later incorporated into nearby Grus as Gamma Gruis.

Ptolemy had catalogued Fomalhaut (Alpha Piscis Austrini) as belonging to both this constellation and Aquarius.

[15] Its companion Fomalhaut b was thought to be the first extrasolar planet ever detected by a visible light image, thanks to the Hubble Space Telescope, but infrared observations have since retracted this claim: it is instead a spherical cloud of dust.

[20] Beta is a white main-sequence star of apparent magnitude 4.29 that is of similar size and luminosity to Fomalhaut but five times as remote,[17] at around 143 ± 1 light-years distant from Earth.

[24] Zeta Piscis Austrini is an orange giant star of spectral type K1III that is located 413 ± 2 light-years distant from Earth.

[16] Lacaille 9352 is a faint red dwarf star of spectral type M0.5V that is just under half the Sun's diameter and mass.