[http://www.davidmalin.com/fujii/source/Cir.html]
Triangulum Australe is a small constellation in the far Southern Celestial Hemisphere. Its name is Latin for ‘the southern triangle,’ which distinguishes it from Triangulum in the northern sky and is derived from the almost equilateral pattern of its three brightest stars. It is bordered by Norma to the north, Circinus to the west, Apus to the south and Ara to the east. It lies near the Pointers (Alpha and Beta Centauri), with only Circinus in between. The constellation is located within the Milky Way, and hence has many stars. A roughly equilateral triangle, it is easily identifiable. Triangulum Australe lies too far south in the celestial southern hemisphere to be visible from Europe, yet is circumpolar from most of the southern hemisphere. In the equatorial coordinate system, the right ascension coordinates of the constellation lie between 14h 56.4m and 17h 13.5m, while the declination coordinates are between −60.26° and −70.51°. Triangulum Australe culminates each year at 9 p.m. on 23 August.
Triangulum Australe, with the alternative name Libella, the level, on Chart XX of Johann Bode’s Uranographia (1801). Bode followed Lacaille in showing a plumb bob attached to the triangle, thereby representing it as a surveyor’s level. Along with the compasses (Circinus) and a set square (Norma) it formed a group of surveying instruments in this part of the sky.
[http://www.ianridpath.com/startales/triangulumaustrale.htm]
Italian navigator Amerigo Vespucci explored the New World at the beginning of the 16th century. He learnt to recognize the stars in the southern hemisphere and made a catalogue for his patron king Manuel I of Portugal, which is now lost. As well as the catalogue, Vespucci wrote descriptions of the southern stars, including a triangle which may be either Triangulum Australe or Apus. This was sent to his patron in Florence, Lorenzo di Pierfrancesco de’ Medici, and published as Mundus Novus in 1504.
The first depiction of the constellation was provided in 1589 by Flemish astronomer and clergyman Petrus Plancius on a 32 1⁄2-cm diameter celestial globe published in Amsterdam by Dutch cartographer Jacob Floris van Langren, where it was called Triangulus Antarcticus and incorrectly portrayed to the south of Argo Navis. His student Petrus Keyzer, along with Dutch explorer Frederick de Houtman, coined the name Den Zuyden Trianghel. Triangulum Australe was more accurately depicted in Johann Bayer’s celestial atlas Uranometria in 1603, where it was also given its current name.
Nicolas Louis de Lacaille portrayed the constellations of Norma, Circinus and Triangulum Australe as a set square and ruler, a compass, and a surveyor’s level respectively in a set of draughtsman's instruments in his 1756 map of the southern stars. Also depicting it as a surveyor’s level, German Johann Bode gave it the alternate name of Libella in his Uranographia.
The Wardaman people of the Northern Territory in Australia perceived the stars of Triangulum Australe as the tail of the Rainbow Serpent, which stretched out from near Crux across to Scorpius. Overhead in October, the Rainbow Serpent ‘gives Lightning a nudge’ to bring on the wet season rains in November.
[http://www.dibonsmith.com/tra_con.htm]
Triangulum Australe
[http://www.astronomytrek.com/star-constellation-facts-triangulum-australe/]
The three brightest stars, Alpha, Beta and Gamma, make up the triangle of the constellation. Readily identified by its orange hue, Alpha Trianguli Australis is a bright giant star of spectral type K2 IIb-IIIa with an apparent magnitude of +1.91 that is the 42nd-brightest star in the night sky. It lies 424 light-years (130 parsecs) away and has an absolute magnitude of −3.68 and is 5500 times more luminous than our sun. With a diameter 130 times that of our sun, it would almost reach the orbit of Venus if placed at the centre of the Solar System. The proper name Atria is a contraction of its Bayer designation.
Beta Trianguli Australis is a double star, the primary being a F-type main-sequence star with a stellar classification of F1V, and an apparent magnitude of 2.85. Lying only 40 light-years (12 parsecs) away, it has an absolute magnitude of 2.38. Its companion, almost 3 arcminutes away, is a 13th magnitude star which may or may not be in orbit around Beta.
The remaining member of the triangle is Gamma Trianguli Australis with an apparent magnitude of 2.87. It is an A-type main sequence star of spectral class A1 V, which lies 180 light-years (55 parsecs) away.
HD 147018 b
[http://www.exoplanetkyoto.org/exohtml/HD_147018_b.html]
HD 147018 is a yellow dwarf with the stellar classification of G9V. It has an apparent magnitude of 8.4 and is about 139 light years distant from the solar system. The star has 88 percent of the Sun’s mass.
Two extrasolar planets were discovered orbiting the star in August 2009. The inner planet has a mass at least 2.12 times that of Jupiter and orbits the star with a period of 44.236 days. The outer planet has at least 6.56 Jupiter masses and completes an orbit around the star every 1,008 days. [http://www.constellation-guide.com/constellation-list/triangulum-australe-constellation/]
EK Trianguli Australis, a dwarf nova of the SU Ursae Majoris type, was first noticed in 1978 and officially described in 1980. It consists of a white dwarf and a donor star which orbit each other every 1.5 hours. The white dwarf sucks matter from the other star onto an accretion disc and periodically erupts, reaching magnitude 11.2 in superoutbursts, 12.1 in normal outbursts and remaining at magnitude 16.7 when quiet. Nova Trianguli Australis 2008 was a slow nova which peaked at magnitude 8.4 in April 2008, before fading to magnitude 12.4 by September of that year.
Triangulum Australe has few deep-sky objects- one open cluster and a few planetary nebulae and faint galaxies:
NGC 6025
[https://en.wikipedia.org/wiki/NGC_6025]
NGC 6025 is an open cluster with about 30 stars ranging from 7th to 9th magnitude. Located 3 degrees north and 1 east of Beta Trianguli Australis, it lies about 2,500 light-years (770 parsecs) away and is about 11 light-years (3.4 parsecs) in diameter. Its brightest star is MQ Trianguli Australis at apparent magnitude 7.1.
NGC 5979, a planetary nebula of apparent magnitude 12.3, has a blue-green hue at higher magnifications, while Henize 2-138 is a smaller planetary nebula of magnitude 11.0:
The planetary nebula NGC 5979
This previously unreleased color image of the planetary nebula NGC 5979 is a composite of raw FITS files made with the ESA/ESO/NASA Photoshop FITS Liberator. The image was composed from four individual exposures taken through: A blue narrow-band filter (502 nm, 460 seconds showing the forbidden OIII line); A green wide-band filter (555 nm, 240 seconds); An orange-red narrow-band filter (658 nm, 1200 seconds showing the forbidden NII line); A red, or near-infrared, wide-band filter (814 nm, 480 seconds).
Stars like the Sun spend most of their life quietly converting hydrogen into helium. However when the hydrogen in the stellar core is exhausted, they start a short phase of much more rapid evolution, growing in size and brightness, to become cooler red giants that begin to eject large amounts of gas and dust as a slow stellar wind.
When the star has lost most of its mass, it heats up again and brightens so that the ejected material begins to glow. At the same time a faster wind sweeps through to clear out the cocoon of obscuring material and so a planetary nebula is born.
[https://www.spacetelescope.org/images/heic0412c/]
ESO 69-6 is a pair of merging galaxies whose contents have been dragged out in long tails by the interaction:
ESO 69-6
The galaxies of this beautiful interacting pair bear some resemblance to musical notes on a stave. Long tidal tails sweep out from the two galaxies: gas and stars were stripped out and torn away from the outer regions of the galaxies. The presence of these tails is the unique signature of an interaction. ESO 69-6 is located in the constellation of Triangulum Australe, the Southern Triangle, about 650 million light-years away from Earth.
[https://www.spacetelescope.org/images/heic0810bz/]
ESO 137-001 is a barred spiral galaxy located in the cluster known as Abell 3627 (Norma Cluster). As the galaxy moves to the center of the cluster, it is stripped by hot gas thus creating a 260,000 light-year long tail. There is evidence of star formation in the tails. The galaxy was discovered by Dr. Ming Sun in 2005:
[https://en.wikipedia.org/wiki/ESO_137-001]
Stripping ESO 137-001
Spiral galaxy ESO 137-001 hurtles through massive galaxy cluster Abell 3627 some 220 million light years away. The distant galaxy is seen in this colorful Hubble/Chandra composite image through a foreground of the Milky Way’s stars toward the southern constellation Triangulum Australe. As the spiral speeds along at nearly 7 million kilometers per hour, its gas and dust are stripped away when ram pressure with the cluster’s own hot, tenuous intracluster medium overcomes the galaxy’s gravity. Evident in Hubble’s near visible light data, bright star clusters have formed in the stripped material along the short, trailing blue streaks. Chandra’s X-ray data shows off the enormous extent of the heated, stripped gas as diffuse, darker blue trails stretching over 400,000 light-years toward the bottom right. The significant loss of dust and gas will make new star formation difficult for this galaxy. A yellowish elliptical galaxy, lacking in star forming dust and gas, is just to the right of ESO 137-001 in the frame.
[https://apod.nasa.gov/apod/ap140328.html]
[https://en.wikipedia.org/wiki/Triangulum_Australe]
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