Piscis Austrinus constellation lies in the southern sky. It is the 60th constellation in size, occupying an area of 245 square degrees. Its name means ‘the southern fish’ in Latin. The constellation is sometimes also called Piscis Australis. It is located in the fourth quadrant of the southern hemisphere (SQ4) and can be seen at latitudes between +55° and -90°. The neighboring constellations are Aquarius, Capricornus, Grus, Microscopium and Sculptor.
[http://www.constellation-guide.com/constellation-list/piscis-austrinus-constellation/]
Piscis Austrinus, called Piscis Notius on the Uranographia of Johann Bode (1801), is shown lying on its back and drinking water from the urn of Aquarius. In its mouth is the bright star Fomalhaut.
Eratosthenes called this the Great Fish and said that it was the parent of the two smaller fishes of the zodiacal constellation Pisces. Like Pisces, its mythology has a Middle Eastern setting that reveals its Babylonian origin.
According to the brief account of Eratosthenes, the Syrian fertility goddess Derceto (the Greek name for Atargatis) is supposed to have fallen into a lake at Bambyce near the river Euphrates in northern Syria, and was saved by a large fish. Hyginus says, in repetition of his note on Pisces, that as a result of this the Syrians do not eat fish but they worship the images of fish as gods. All the accounts of this constellation’s mythology are disappointingly sketchy.
[http://www.ianridpath.com/startales/piscisaustrinus.htm]
Pisces Austrinus originated with the Babylonian constellation simply known as the Fish (MUL.KU).
In Greek mythology, 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, this fish saved the life of the Egyptian goddess Isis, so she placed this fish and its descendants into the heavens as constellations of stars.
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.
Piscis Austrinus: First magnitude Fomalhaut far outshines the other stars of Piscis Austrinus, the Southern Fish. The upper stars of Grus, the Crane, form a downward line at lower right. while Sculptor lies to the lower left, Aquarius to the upper left.
[http://stars.astro.illinois.edu/sow/psa-t.html]
DSS image of Fomalhaut, field of view 2.7×2.9 degrees
The constellation’s only star brighter than 4th magnitude is Fomalhaut, which is a first-magnitude star and is the 18th brightest star in the night sky. It has had various names ascribed to it through time. Its modern name derives from Arabic ‘fum al-ḥawt,’ meaning ‘mouth of the [Southern] Fish,’ a translation of how the classical astronomer Ptolemy labeled it. Fomalhaut is a class A star on the main sequence approximately 25 light-years (7.7 pc) from Earth as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
At a declination of −29.6°, Fomalhaut is located south of the celestial equator, and hence is best viewed from the Southern Hemisphere. However, its southerly declination is not as great as that of stars such as Acrux, Alpha Centauri and Canopus, meaning that, unlike them, Fomalhaut is visible from a large part of the Northern Hemisphere as well. Its declination is greater than that of Sirius and similar to that of Antares. At 40°N, Fomalhaut rises above the horizon for eight hours and reaches only 20° above the horizon, while Capella which rises at approximately the same time will stay above the horizon for twenty hours. From England the star never appears much brighter than magnitude 2.2 due to it being so close to the horizon, and from southern Alaska or Scandinavia it never rises above the horizon at all. Fomalhaut can be located in these northern latitudes by the fact that the western (right-hand) side of the Square of Pegasus points to it. Continue the line from Beta to Alpha Pegasi towards the southern horizon: Fomalhaut is about 45˚ south of Alpha Pegasi, with no bright stars in between.
Debris ring around Fomalhaut showing location of planet Fomalhaut b- imaged by
Hubble Space Telescope’s coronagraph.
Fomalhaut is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk. On November 13, 2008, astronomers announced an object, which they assumed to be an extrasolar planet, orbiting just inside the outer debris ring. This was the first extrasolar orbiting object to be seen with visible light, captured by the Hubble Space Telescope. A planet’s existence had been previously suspected from the sharp, elliptical inner edge of that disk. The mass of the planet, Fomalhaut b, was estimated to be no more than three times the mass of Jupiter but at least the mass of Neptune. There are indications that the orbit is not apsidally aligned with the dust disk, which may indicate that additional planets may be responsible for the dust disk’s structure. Fomalhaut is the third brightest star (as viewed from Earth) known to have a planetary system, after the Sun and Pollux.
Fomalhaut, K-type star TW Piscis Austrini (Fomalhaut B) and M-type star LP 876-10 (Fomalhaut C) constitute a triple system even though the companions are separated by several degrees. Fomalhaut B 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. It lies 0.28 parsecs (0.91 light years) away from Fomalhaut. Fomalhaut C is a red dwarf of spectral type M4V, and located even further from Fomalhaut A than Fomalhaut B- about 5.7° away from Fomalhaut A in the sky in the neighboring constellation Aquarius, whereas both Fomalhaut A and Fomalhaut B are located in constellation Piscis Austrinus. Its current separation from Fomalhaut A is about 0.77 parsecs (2.5 light years), and it is currently located 0.987 parsecs (3.2 light years) away from (Fomalhaut B).
[https://en.wikipedia.org/wiki/Fomalhaut#Fomalhaut_B_.28TW_Piscis_Austrini.29]
Epsilon Piscis Austrini is the second brightest star in the constellation. It is a blue-white main sequence dwarf belonging to the spectral class B8V. It has an apparent visual magnitude of 4.18 and is approximately 744 light years distant from Earth.
Delta Piscis Austrini is the third brightest star in Piscis Austrinus. It is really a multiple star system with the stellar classification G8III. The primary component in the system is a yellow giant. The system has an apparent magnitude of 4.20 and is about 170 light years distant from the Sun.
Beta Piscis Austrini is the fourth brightest star in the constellation. It is another multiple star system. It has an apparent visual magnitude of 4.29 and is approximately 148 light years distant from Earth. The system has the stellar classification of A1V, matching the spectrum of a white main sequence dwarf.
[http://www.constellation-guide.com/constellation-list/piscis-austrinus-constellation/]
Lacaille 9352 is a faint red dwarf star which is a mere 10.74 light-years away. At magnitude 7.34, it is too dim to be seen with the naked eye:
Lacaille 9352
Lacaille 9352 is a nearby red dwarf in the constellation Piscis Austrinus close to the border with Sculptor. Lacaille 9352 has the fourth highest known proper motion, moving a total of 6.898" per year. Its closest neighbor is the EZ Aquarii system, 4.21 light-years (1.29 parsecs) away.
[http://www.daviddarling.info/encyclopedia/L/Lacaille_9352.html]
Hickson Compact Groups are groups of galaxies located in Piscis Austrinus:
Hickson Compact Group 90
Scanning the skies for galaxies, Canadian astronomer Paul Hickson and colleagues identified some 100 compact groups of galaxies, now appropriately called Hickson Compact Groups (HCGs). This sharp Hubble image shows one such galaxy group, HCG 90, in startling detail. Three galaxies are revealed to be strongly interacting: a dusty spiral galaxy stretched and distorted between a pair of large elliptical galaxies. The close encounter will trigger furious star formation. On a cosmic timescale, the gravitational tug of war will eventually result in the merger of the trio into a large single galaxy. The merger process is now understood to be a normal part of the evolution of galaxies, including our own Milky Way. HCG 90 lies about 100 million light-years away in the constellation Piscis Austrinus. This Hubble view spans about 80,000 light-years at that estimated distance. Of course, Hickson Compact Groups also make for rewarding viewing for Earth-bound astronomers with more modest sized telescopes.
[http://apod.nasa.gov/apod/ap090313.html]
This is a picture of hot intergalactic gas, in Piscis Austrinus, as if it formed ‘rivers of gravity:’
Four independent teams of scientists have detected intergalactic gas with temperatures in the range 300,000 to 5 million degrees Celsius by observing quasars with the Chandra X-ray Observatory. An artist’s rendering illustrates how X-rays from a distant quasar dim as they pass through a cloud of the intergalactic gas. By measuring the amount of dimming due to oxygen and other elements in the cloud - see the spectrum of the quasar PKS 2155-304 in the inset - astronomers were able to estimate the temperature, density and mass of the absorbing gas cloud.
Observations of PKS 2155 and the quasar H1821+643 by an Ohio State group revealed various parts of the hot gas system. One of these appears to be a filament in which the Milky Way and Andromeda galaxies are embedded, whereas other detected portions are at distances of a few billion light years from Earth.
The hot gas, which appears to lie like a fog in channels carved by rivers of gravity, has been hidden from view since the time galaxies formed. It is thought that this gas forms part of a gigantic system, or web, of hot gas and dark matter that defines the cosmic landscape. The hot gas part of this system could contain more material than all the stars in the universe. Ultraviolet telescopes had detected cooler components of the hot gas system, but most of it is now known to be detectable only with an extremely sensitive X-ray telescope.
The hot gas detected by Chandra can be used to trace the more massive dark matter component. Eventually, astronomers will be able to use the hot gas to map of the distribution of dark matter in the universe and perhaps understand its origin.
[http://chandra.harvard.edu/photo/2002/igm/index.html]
[https://en.wikipedia.org/wiki/Piscis_Austrinus]
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