One of the most magnificient constellations of the southern hemisphere.
It stretches from RA = -30 degrees to RA = -65 degrees and DECL = 11h10m
to little more than Decl= 15h, covering a quite large and very interesting
part of the sky.
At the northern border Hydra is located. At the western border you find Antlia, Vela and Carina from north to south. The southern border neighbours to Musca, Crux, which is nearly embedded into Centaurus and Circinus at the south eastern border. Finally to the east the neighbour constellations are Lupus and Libra.
Centaurus is best known for its brightest star alpha Cen which is the second closest star to our sun. If one draws a line from alpha Cen to beta Cen (also called Hadar) and follows that line it leads directly to the Southern Cross stars beta Cru and delta Cru. This can be used to locate the true Southern Cross as another "False Cross" is formed by i Car, eta Car, delta Vel and kappa Vel.
But there a more interesting objects to an observer and even simple star sweeping can be rewarding as the Milky Way runs through the southern part of the constellation. Especially the regions around alpha Cen and beta Cen are magnificient: the clouds of stars of the Milky Way are brilliant, yet sometimes obscured by clouds of interstellar dusts, which makes observing even more fascinating.
Stars and objects
The best known star of the constellation alpha Cen (arab.:
foot of the centaur), known as Rigil Kentaurus
(often short Rigil Kent), was not only long thought to be the closest
star to our sun but is as well an occulting binary system. When
viewed with the naked eye the alpha Cen looks like a very
bright single star (showing a brightness of -0.3 mag which makes it
the 3rd brightest star in the sky). With a small scope the
components of the binary system can be split into a -0.1 mag yellow star
(G2V) and a 1.33 mag orange star (K1V). Both revolve each other with a
period of 80 years. This system lies in a distance of 4.3 light years.
Even closer lies Proxima Cen, a red dwarf of 11th mag,
the closest star to our our sun. Proxima Cen is about
2 degrees apart from its brighter companions.
To split the pair gamma Cen telescopes with an aperture of at least 300mm are necessary. The both components show a brightness of 3.1 mag and 3.2 mag, respectively. The two stars revolve each other with a period of about 85 years (older sources list values about 203 years).
Another double is k Cen, also labelled as 3 Cen. It consists of a pair of blue-white stars of 5th and 6th mag. The pair is nice object for small scopes as the both stars show a wide separation.
North of delta Cen lies the double D Cen. The two stars with a brightness of 5.6 mag and 6.8 mag can easily be resolved in small scopes.
The faint halo around the star lambda Cen is listed as IC 2944.
The planetary nebula NGC 3918 shows a small disk with a blue-green color that resembles the color of our planet Uranus. It was called Blue Planetary by Johann Herschel.
The famous globular star cluster omega Cen (NGC 5139) is the largest and brightest in the sky. It takes an area on the sky even larger than the full Moon. When viewed with the naked eye it appears as a somewhat fuzzy star of about 4th mag showing a slightly elliptical shape. As the object is large enough even in binoculars the cluster begins to reveal its true nature. Small telescopes reveal stars at the borders of that object, with larger scopes more and more of the globular cluster can be detected resolving more of the outer borders into a mass of stars. With about 16,000 light years this globular star cluster is also one the closest globular clusters to us.
A fascinating object is the peculiar galaxy NGC 5128, which became famous not only for its appearance but also for its strong radio source Centaurus A. In small scopes this galaxy appears as small fuzzy patch of 7th mag. Long exposure photographs reveal an elliptical galaxy with a broad dark lane of dust running through it. The galaxy lies in a distance of about 15 million light years (which makes it the nearest of all known radio sources).
According to Eratosthenes (Catasterism.40) Centaurus represents the centaur Chiron. Although an centaur Chiron has been a good doctor and astronomer. So he has been the teacher of many famous poeple as Hercules, Achilleus, Aeskulapios and many more (see Xenophon de venat. in init. p. 972. Opp). Chiron died from one of the arrows of Hercules in an accident: one of the arrows fell out of Hecules quiver; it hit Chiron on the foot. The head of the arrow had been poisoned with the blood of the lernaic snake. Chiron found no way of healing himself. Being immortal (due to his ancestors) he suffered great pain with no chance for redemption. Finally he asked from the gods the favor to die. Because he lived his life with so high virtue Zeus himself placed him under the stars.