Deux constellations voisines de l'hémisphère celeste Sud: la Couronne Australe et le Télescope.
Une vue de chaque constellation, un zoom sur une partie de la Couronne Australe (NGC 6723 de la constellation du Sagittaire et un nuage sombre), et une vue regroupant ces deux constellations voisines.
La Couronne Australe (Source Wikipedia): Répertoriée par Ptolémée, le nom de cette constellation fait pendant à celui de la Couronne boréale. Ses étoiles sont en effet disposées selon un arc-de-cercle qui rappelle une couronne. Il s'agirait de celle du Sagittaire, tout proche.
C'est une constellation faible (mag 4 à 5) et sa forme est nettement moins marquante que sa sœur la Couronne boréale. La constellation se repère à partir du Scorpion, plein Est par rapport à la queue, et du Sagittaire, plein Sud par rapport au cou Nunki.
Le Télescope (Source Wikipedia): Cette constellation fut introduite par
Nicolas-Louis de Lacaille en 1752 pour désigner un pan de ciel sans dénomination. Comme plusieurs autres constellations créées par Lacaille, elle porte le nom d'un appareil scientifique.
La constellation du Télescope héberge une nébuleuse planétaire, IC 4699, un amas globulaire, NGC 6584, et plusieurs galaxies, NGC 6725, NGC 6761, NGC 6754 et NGC 6861.
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Two neighboring constellations of the southern celestial hemisphere: Corona Australis and Telescopium.
A view of each constellation, a partial zoom on Corona Australis (NGC 6723 from Sagittarius and a dark cloud), and a grouping view of these two neighbors.
Corona Australis (Source Wikipedia) is a constellation in the Southern Celestial Hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax.
Although fainter than its northern counterpart, the oval- or horseshoe-shaped pattern of its brighter stars renders it distinctive. Alpha and Beta Coronae Australis are the two brightest stars with an apparent magnitude of around 4.1. Epsilon Coronae Australis is the brightest example of a W Ursae Majoris variable in the southern sky. Lying alongside the Milky Way, Corona Australis contains one of the closest star-forming regions to the Solar System—a dusty dark nebula known as the Corona Australis Molecular Cloud, lying about 430 light years away. Within it are stars at the earliest stages of their lifespan. The variable stars R and TY Coronae Australis light up parts of the nebula, which varies in brightness accordingly.
The name of the constellation was entered as "Corona Australis" when the International Astronomical Union (IAU) established the 88 modern constellations in 1922.[5][6] In 1932, the name was instead recorded as "Corona Austrina" when the IAU's commission on notation approved a list of four-letter abbreviations for the constellations. The four-letter abbreviations were repealed in 1955. The IAU presently uses "Corona Australis" exclusively.
Telescopium (Source Wikipedia) is a minor constellation in the southern celestial hemisphere, one of twelve named in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. Its name is a Latinized form of the Greek word for telescope. Telescopium was later much reduced in size by Francis Baily and Benjamin Gould.
The brightest star in the constellation is Alpha Telescopii, a blue-white subgiant with an apparent magnitude of 3.5, followed by the orange giant star Zeta Telescopii at magnitude 4.1. Eta and PZ Telescopii are two young star systems with debris disks and brown dwarf companions. Telescopium hosts two unusual stars with very little hydrogen that are likely to be the result of two merged white dwarfs: PV Telescopii, also known as HD 168476, is a hot blue extreme helium star, while RS Telescopii is an R Coronae Borealis variable. RR Telescopii is a cataclysmic variable that brightened as a nova to magnitude 6 in 1948.
History: Telescopium was introduced in 1751–52 by Nicolas-Louis de Lacaille with the French name le Telescope, depicting an aerial telescope, after he had observed and catalogued 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised 14 new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honored instruments that symbolised the Age of Enlightenment. Covering 40 degrees of the night sky, the telescope stretched out northwards between Sagittarius and Scorpius. Lacaille had Latinised its name to Telescopium by 1763.
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