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Piscis Austrinus is a
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 ...
in the
southern celestial hemisphere The southern celestial hemisphere, also called the Southern Sky, is the Southern Hemisphere, southern half of the celestial sphere; that is, it lies south of the celestial equator. This arbitrary sphere, on which seemingly fixed stars form cons ...
. The name is
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
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 Piscis Notius. Piscis Austrinus was one of the 48 constellations listed by the 2nd-century astronomer
Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...
, and it remains one of the 88 modern constellations. The stars of the modern constellation Grus once formed the "tail" of Piscis Austrinus. In 1597 (or 1598), Petrus Plancius carved out a separate constellation and named it after the crane. It is a faint constellation, containing only one
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 ...
brighter than 4th magnitude: Fomalhaut, which is 1st magnitude and the 18th-brightest star in the
night sky The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include moonlig ...
. Fomalhaut is surrounded by a
circumstellar disk A Circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the res ...
, and possibly hosts a planet. Other objects contained within the boundaries of the constellation include Lacaille 9352, one of the brightest
red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...
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.


Origins

Pisces Austrinus originated with the Babylonian constellation simply known as the Fish (MUL.KU). 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. 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. 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 Summer or summertime is the hottest and brightest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, daylight hours are the longest and darkness hours are the shortest, with day ...
and
winter solstice The winter solstice, or hibernal solstice, occurs when either of Earth's geographical pole, poles reaches its maximum axial tilt, tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern Hemisphere, Northern and So ...
s, respectively. In
Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...
, this constellation is known as the Great Fish and it is portrayed as swallowing the water being poured out by Aquarius, the water-bearer constellation. The two fish of the constellation Pisces are said to be the offspring of the Great Fish. In
Egyptian mythology Egyptian mythology is the collection of myths from ancient Egypt, which describe the actions of the Egyptian pantheon, Egyptian gods as a means of understanding the world around them. The beliefs that these myths express are an important part ...
, this fish saved the life of the Egyptian goddess
Isis Isis was a major goddess in ancient Egyptian religion whose worship spread throughout the Greco-Roman world. Isis was first mentioned in the Old Kingdom () as one of the main characters of the Osiris myth, in which she resurrects her sla ...
, so she placed this fish and its descendants into the heavens as constellations of stars. In the 5th century BC, Greek historian
Ctesias Ctesias ( ; ; ), also known as Ctesias of Cnidus, was a Greek physician and historian from the town of Cnidus in Caria, then part of the Achaemenid Empire. Historical events Ctesias, who lived in the fifth century BC, was physician to the Acha ...
wrote that the fish was said to have lived in a lake near Bambyce in Syria and had saved Derceto, daughter of
Aphrodite Aphrodite (, ) is an Greek mythology, ancient Greek goddess associated with love, lust, beauty, pleasure, passion, procreation, and as her syncretism, syncretised Roman counterpart , desire, Sexual intercourse, sex, fertility, prosperity, and ...
, and for this deed was placed in the heavens. For this reason, fish were sacred and not eaten by many Syrians.


Characteristics

Piscis Austrinus is a constellation bordered by
Capricornus Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat Horn (anatomy), horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is hal ...
to the northwest,
Microscopium Microscopium ("the Microscope") is a minor constellation in the southern celestial hemisphere, one of twelve created in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. The name ...
to the southwest, Grus to the south,
Sculptor Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...
to the east, and Aquarius to the north. Its recommended three-letter abbreviation, as adopted by the
International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
in 1922, is "PsA".
Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...
called the constellation ''Ichthus Notios'' "Southern Fish" in his ''
Almagest The ''Almagest'' ( ) is a 2nd-century Greek mathematics, mathematical and Greek astronomy, astronomical treatise on the apparent motions of the stars and planetary paths, written by Ptolemy, Claudius Ptolemy ( ) in Koine Greek. One of the most i ...
''; this was Latinised to Piscis Notius and used by German celestial cartographers Johann Bayer and Johann Elert Bode. Bayer also called it Piscis Meridanus and Piscis Austrinus, while French astronomer
Nicolas-Louis de Lacaille Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a kingdom of France, French astronomer and geodesist who named 14 out of the IAU designated constellations, 88 constellations. From 1750 ...
called it Piscis Australis. English
Astronomer Royal Astronomer Royal is a senior post in the Royal Households of the United Kingdom. There are two officers, the senior being the astronomer royal dating from 22 June 1675; the junior is the astronomer royal for Scotland dating from 1834. The Astro ...
John Flamsteed John Flamsteed (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, ''Catalogus Britannicus'', and a star atlas called '' Atlas ...
went with Piscis Austrinus, which was followed by most subsequently. The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of four segments (''illustrated in infobox''). In the
equatorial coordinate system The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of astronomical object, celestial objects. It may be implemented in spherical coordinate system, spherical or Cartesian coordinate system, rect ...
, the
right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...
coordinates of these borders lie between and , while the
declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...
coordinates are between −24.83° and −36.46°. The whole constellation is visible to observers south of latitude 53°N.


Features


Stars

Ancient astronomers counted twelve stars as belonging to Piscis Austrinus, though one was later incorporated into nearby Grus as Gamma Gruis. Other stars became part of Microscopium. Bayer used the
Greek letters The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to systematically write vowels as we ...
alpha Alpha (uppercase , lowercase ) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter ''aleph'' , whose name comes from the West Semitic word for ' ...
through mu to label the most prominent stars in the constellation. Ptolemy had catalogued Fomalhaut (Alpha Piscis Austrini) as belonging to both this constellation and Aquarius. Lacaille redrew the constellation as it was poorly visible from Europe, adding pi, and relabelling
gamma Gamma (; uppercase , lowercase ; ) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter normally repr ...
,
delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...
and
epsilon Epsilon (, ; uppercase , lowercase or ; ) is the fifth letter of the Greek alphabet, corresponding phonetically to a mid front unrounded vowel or . In the system of Greek numerals it also has the value five. It was derived from the Phoenic ...
as epsilon,
eta Eta ( ; uppercase , lowercase ; ''ē̂ta'' or ''ita'' ) is the seventh letter of the Greek alphabet, representing the close front unrounded vowel, . Originally denoting the voiceless glottal fricative, , in most dialects of Ancient Greek, it ...
and gamma, respectively. However, Baily and Gould did not uphold these changes as Bayer's original chart was fairly accurate. Bode added
tau Tau (; uppercase Τ, lowercase τ or \boldsymbol\tau; ) is the nineteenth letter of the Greek alphabet, representing the voiceless alveolar plosive, voiceless dental or alveolar plosive . In the system of Greek numerals, it has a value of 300 ...
and
upsilon Upsilon (, ; uppercase Υ, lowercase υ; ''ýpsilon'' ) or ypsilon is the twentieth letter of the Greek alphabet. In the system of Greek numerals, has a value of 400. It is derived from the phoenician alphabet, Phoenician Waw (letter), waw ...
. Flamsteed gave 24 stars Flamsteed designations, though the first four numbered became part of Microscopium. Within the constellation's borders, there are 47 stars brighter than or equal to
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), ...
 6.5. Traditionally representing the mouth of the fish, Fomalhaut is the brightest star in the constellation and the 18th-brightest star in the night sky, with an apparent magnitude of 1.16. Located 25.13 ± 0.09
light-year 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 Astr ...
s away, it is a white main-sequence star that is 1.92 ± 0.02 times as massive and 16.63 ± 0.48 as luminous as the Sun. Its companion
Fomalhaut b TW Piscis Austrini (also known as Fomalhaut B) is a main sequence star in the constellation Piscis Austrinus. It lies relatively close to the Sun, at an estimated distance of . To an observer on Earth the star is visually separated from i ...
was thought to be the first
extrasolar planet 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 detect ...
ever detected by a visible light image, thanks to the
Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...
, but infrared observations have since retracted this claim: it is instead a spherical cloud of dust. TW Piscis Austrini can be seen close by and is possibly associated with Fomalhaut as it lies within a light-year of it. Of magnitude 6.5, it is a BY Draconis variable. The second-brightest star in the constellation, Epsilon Piscis Austrini is a blue-white star of magnitude +4.17. Located 400 ± 20 light-years distant, it is a blue-white main-sequence star 4.10 ± 0.19 times as massive as the Sun, and around 661 times as luminous.
Beta Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...
,
Delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...
and
Zeta Zeta (, ; uppercase Ζ, lowercase ζ; , , classical or ''zē̂ta''; ''zíta'') is the sixth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 7. It was derived from the Phoenician alphabet, Phoenician letter zay ...
constitute the ''Tien Kang'' ("heavenly rope") in
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
. 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, at around 143 ± 1 light-years distant from Earth. Delta Piscis Austrini is a double star with components of magnitude 4.2 and 9.2. The brighter is a yellow giant of spectral type G8 III. It is a red clump star that is burning helium in its core. It is 172 ± 2 light-years distant from Earth. Zeta Piscis Austrini is an orange giant star of spectral type K1III that is located 413 ± 2 light-years distant from Earth. It is a suspected variable star. S Piscis Austrini is a long-period Mira-type variable red giant which ranges between magnitude 8.0 and 14.5 over a period of 271.7 days, and V Piscis Austrini is a semi-regular variable ranging between magnitudes 8.0 and 9.0 over 148 days. Lacaille 9352 is a faint
red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...
star of spectral type M0.5V that is just under half the Sun's diameter and mass. A mere 10.74 light-years away, it is too dim to be seen with the naked eye at magnitude 7.34. In June 2020 two super-Earth planets were discovered via radial velocity method. Exoplanets have been discovered in five other star systems in the constellation. HD 205739 is a yellow-white main-sequence star of spectral type F7 V that has a planet around 1.37 times as massive as Jupiter orbiting it with a period of 279 days, and a suggestion of a second planet. HD 216770 is an orange dwarf accompanied by a Jupiter-like planet every 118 days. HD 207832 is a star of spectral type G5V with a diameter and mass about 90% of that of the Sun, and around 77% of its luminosity. Two gas giant planets with masses around 56% and 73% that of Jupiter were discovered in 2012 via the radial velocity method. With orbits of 162 and 1156 days, they average around 0.57 and 2.11 astronomical units away from their star. WASP-112 and WASP-124 are two sun-like stars that have planets discovered by transit.


Deep sky objects

NGC 7172, NGC 7174 and NGC 7314 are three galaxies of magnitudes 11.9, 12.5 and 10.9, respectively. NGC 7259 is another
spiral galaxy Spiral galaxies form a galaxy morphological classification, class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''
, which hosted a
supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...
SN 2009ip—in 2009. At
redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and e ...
z = 0.116, the BL Lacertae object PKS 2155-304 is one of the brightest blazars in the sky.


See also

* Piscis Austrinus in Chinese astronomy


Notes


References


External links


Warburg Institute Iconographic Database (medieval and early modern images of Piscis Austrinus under the name Piscis magnus)


{{DEFAULTSORT:Piscis Austrinus Constellations Southern constellations Constellations listed by Ptolemy