Constellations: Piscis Austrinus 'the Southern Fish' Content from the guide to life, the universe and everything

Constellations: Piscis Austrinus 'the Southern Fish'

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The shield of the Science, Mathematics and Engineering faculty of the h2g2 University.Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
Camelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus
Cepheus | Cetus | Chamæleon | Circinus | Columba | Coma Berenices | Corona Australis | Corona Borealis | Corvus
Crater | Crux | Cygnus | Delphinus | Dorado | Draco | Equuleus | Eridanus | Fornax | Gemini | Grus | Hercules | Horologium
Hydra | Hydrus | Indus | Lacerta | Leo | Leo Minor | Lepus | Libra | Lupus | Lynx | Lyra | Mensa | Microscopium | Monoceros
Musca | Norma | Octans | Ophiuchus | Orion | Pavo | Pegasus | Perseus | Phoenix | Pictor | Pisces | Piscis Austrinus
Puppis | Pyxis | Reticulum | Sagitta | Sagittarius | Scorpius | Sculptor | Scutum | Serpens | Sextans | Taurus
Telescopium | Triangulum | Triangulum Australe | Tucana | Ursa Major | Ursa Minor | Vela | Virgo | Volans | Vulpecula
Superb unreturning tide,
those silent waters weave for him
a fluctuant mutable world and dim...

- Rupert Brooke
Name:Piscis Austrinus (Latin: 'Southern Fish')
Genitive:Piscis Austrini
Short form:PsA
Area:245 sq deg
Co-ordinates1:Right Ascension 23h, Declination −39°

On a bright moonlit night (or in an place containing street lights) this area of the sky, lying some 30 degrees south of the celestial equator, may look empty except for Fomalhaut which appears as a lone beacon in the autumn skies. Those in northern latitudes may find Piscis Austrinus2 is a bit too far south to observe; however more southerly viewers, under dark sky conditions with a pair of binoculars, will see plenty of stars.

The ancient observers connected these faint stars in their minds to make a fish lying on its back with its mouth open. Located below Aquarius, next to Microscopium and north of Grus, this constellation lies south of the Zodiac and should not be confused with Pisces. Some early star charts showed the water from Aquarius pouring into the open mouth. Stars of the adjacent constellation Grus, the Crane, were part of Piscis Austrinus until Astronomer Johann Bayer created Grus in the 17th Century. Several of Grus' stars carry Arabic names that reflect their previous inclusion in Piscis Austrinus.


This fish was once thought to have been connected to the Assyrian fish god Dagon, and before that to the figure Oannes. Oannes, they said, taught all manner of knowledge during the day, but at night turned into a fish and slept in the sea.

In one Greek myth two fish swam up and rescued Aphrodite and Eros when they were besieged by a monster on the river bank. Eratosthenes postulated that these were the offspring of what he labelled 'The Great Southern Fish'. These two fish became the Zodiacal constellation Pisces.


Beta is a line-of-sight double. The two stars of +4.3 and +7.9 magnitude are not physically connected.

A small grouping of fifth and sixth magnitude stars - five in all - including tau, mu, upsilon and nu Piscis Austrini, form a small bright asterism near the tail of the fish.

Eta, theta, iota and mu Piscis Austrini were known in Chinese astrology as Tien Tsien, 'Heavenly Cash'.


Alpha Piscis Austrini, Fomalhaut, is the brightest and only first magnitude star. This was one of four 'Royal Stars' in Mesopotamia. The Romans also observed this star from some of their southern provinces and called it Piscis Meridiani. The word Fomalhaut is derived from 'Fom al Hat' which translates as 'the mouth of the fish'. It has a ring some 15 AU (Astronomical Units) in diameter which is irregular in shape. Like the braided ring of Saturn, it was speculated that some unseen shepherd planets were determining the shape of this ring. In November 2008 Astronomy Picture of the Day featured Fomalhaut's dust disc, confirming a gas giant planet at 115 AU distance from the star.

Lacaille 9352

This seventh magnitude red dwarf, located near pi Piscis Austrini, is in the list of ten closest stars. It was originally hoped that a planetary system would be found here but repeated attempts to find one proved to be unsuccessful.

   Star  DesignationName or
catalogue number
Brightness (m)Distance
(light years3)
Spectral Classification
α PsA Alpha Fomalhaut+1.1622 A3
ε PsA EpsilonHD 214748+4.17744B8
δ PsA Delta HD 216763+4.21160G8
β PsA Beta HD 213398+4.29170 A0
ι PsA Iota HD 206742+4.3445A0
γ PsA GammaHD 206742+4.46222A0
μ PsA Mu HD 210049+4.5130A2
τ PsA Tau HD 210302+4.9262F6
υ PsA Upsilon HD 210066+4.99 360F0
θ PsA Theta HD 2071555.02540 A1
π PsA Pi HD 217792+5.1163A6
η PsA Eta HD 209014+5.421,012B8
lac9352 Lacaille9352 HD 217987+7.3410.74M0



The New General Catalogue, by J Dreyer, was published by the Royal Astronomical Society in the late 19th Century. It was expanded to include two Index Catalogues (IC). This list of star clusters, nebulae and galaxies was revised again in 1973, and is continually updated by the NGC/IC Project.

Cat. NO.ClassBrightness (m)Distance
NGC 7172 S0 +12.0103
NGC 7174 Sab+11.6106
NGC 7259Sb +13.366
NGC 7262 Sa +13.9 346
NGC 7277 Sb +13.5165
NGC 7306 SBb +12.5143
NGC 7314Sc +11.0200
NGC 7567S0 +14.8174
IC 5131 Sb0+12.4105
IC 5156Sb+13.0111
IC 5157 Elliptical+12.5185
IC 5169 S0a+12.9126
IC 5262 Elliptical+13.4366
IC 5269 S0+13.075
IC 5270 SC+13.176
IC 5271 SbD+12.664

Extrasolar Planets

Three planetary systems had been found in this constellation by 2008. The size of these extrasolar planets is comparable to the mass of Jupiter, our Solar System's largest planet, known by astronomers as the 'Jovian scale'. Some exoplanets have been given proper names by the IAU. Fomalhaut b has been anointed Dagon, after the fish god of fertility and agriculture in Phoenician mythology.

Star NamePlanet
FomalhautFomalhaut b/DagonApprox 872 yrs 0.5 115 AU2008
HD 216770HD 216770 b118.45 days0.6470.46 AU2003
HD 205739HD 205739 b279.8 days1.370.896 AU2008
HD 207832HD 207832 b162 days0.560.57 AU2012
HD 207832HD 207832 c1,155 days0.732.1 AU2012
WASP-112WASP-112 b3.04 days0.880.04 AU2014
WASP-124WASP-124 b3.37 days0.60.05 AU2016

Meteor Shower

The streak of light of the shooting star is caused by small specks of dust which burn up from friction with the air in the upper reaches of the Earth's atmosphere. The dust is usually from the trails of comets that have crossed the Earth's orbit leaving debris behind them. If the tracks of a number of meteors can be traced back to a common point of intersection, they are named from the star nearest to that point. This Constellation is host to seven minor meteor showers all of which occur in July and August. The most well known, Alpha Pisces Australids, was discovered in 1865 by Alexander S Herschel. Due to the orbital mechanics involved, if you live south of Earth's equator you will be more likely to observe these meteors. Here are the dates of these meteor showers.

Alpha Pisces Australids16 July-13 August
Theta Pisces Australids12 August-14 August
Beta Pisces Australids14 July-22 July
Lamba Pisces Australids 5 August-14 August
Epsilon Pisces Australids13 August-14 August
Pi Pisces Australids28 July-3 August
20 Pisces Australids 8 August-9 August
1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2Also called Piscis Australis.3A light year is the distance light travels in one year, roughly 5.88 trillion (short scale, 5.879×1012) miles or 9.46 trillion (short scale, 9.461×1012) kilometres.

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