Centaurus is a prominent southern constellation. It is one of the major constellations along the southern Milky Way. For southern observers, it signifies the coming of fall. Crux, the Southern Cross, lies on the southern boundary of Centaurus. Along with Centaurus, the constellation Sagittarius is also a centaur.
History and Mythology
A centaur is a creature which dates from the ancient Greeks and is half man, half beast. Unlike most other centaurs, who were war loving, Chiron was a wise and gentle creature. He was skilled in music, hunting, and medicine. He educated Jason (who searched for the Golden Fleece), Achilles, Hercules and Aesculapius.
One of Chiron's accomplishments was to create the constellations. Chiron placed the stars into groups allowing people to read the patterns in the sky. They could now predict the seasons by following the stars. Chiron created a southern constellation, Centaurus, to honor himself.
Notable Stars
Centaurus contains Alpha Centauri, the third brightest star in the sky and the closest star system to our own. Alpha Centauri is 4.3 light-years away. It is also known as Rigel Kentaurus, the "foot of the centaur" (not to be confused with Rigel in Orion). It is a triple star system with yellow components of magnitude 0.0 and 1.2. The two brighter components have an 80-year orbital period, over which their apparent separation varies from 2 to 22 arcseconds. The brighter component is a remarkably sunlike star; its companion has about half the Sun's luminosity.
The third member of the system is Proxima Centauri, a red dwarf in a long-period orbit around Alpha Centauri. It is currently the closest of the three, about a tenth of a light year closer to us, and appears at 13th magnitude, about 2 degrees south of the brighter pair. It has 0.0008 of the Sun's luminosity.
Beta Centauri is a bluish star of magnitude of 0.61, and is the 10th brightest star in the sky. Also called Hadar, which comes from the Arabic word for "ground", this star is 335 light years away and therefore bright because it is truly luminous.
Clusters, Nebulae, and Galaxies
The largest and richest globular cluster in the sky is Omega Centauri. It can be seen with the naked eye as a fuzzy ball as large as the full moon. In a small telescope it is a stunning sight, in which thousands of individual stars can be seen.
In areas of Centaurus not obstructed by the Milky Way, there is a good selection of galaxies, some of which are southern members of the Coma-Virgo galaxy cluster. Two are of special interest to amateur observers. Centaurus A (NGC 5128) is a peculiar, edge-on galaxy with a large dust lane extending across the nucleus. At 7th magnitude, it is the fifth brightest star in the sky, and is also known to be a radio source. Its strange shape is the result of a collision between a larger elliptical galaxy, which is devouring a smaller spira. NGC 4945 is a bright, edge-on spiral visible in any medium size telescope.
Also notable is the region of nebulosity surrounding the star Lambda Centauri. This region, dubbed the "Running Chicken" nebula, is IC 2948. The associated star cluster is IC 2944.
Located near IC 2948 is the Pearl Cluster, NGC 3766, a very dense 5th-magnitude open cluster that lies at a distance of 5500 light years. NGC 5286 is an 8th-magnitude globular cluster located 4° SW of Zeta Centauri. NGC 3918 is a bright, 8th-magnitude planetary nebula, often called the "Blue Planetary" due to its beautiful rich blue color.