Centaurus the Centaur

Written by Pam Eastlick of the University of Guam.

Although Crux the Southern Cross is probably more famous in northern latitudes, there is no question that Centaurus the Centaur is the most magnificent of the southern constellations. It's the ninth largest constellation and it contains two of the ten brightest stars. No other constellation can make this claim although Orion the Hunter and Crux the Southern Cross each contain two of the twenty brightest stars. Centaurus also contains the closest star to the sun, the best globular cluster, and has its own meteor shower. It does not contain any Messier objects because the constellation is too far south for Messier to have seen it.

That wasn't the case 2,000 years ago, however, when precession had carried the southern stars of spring into the view of the ancient Greeks. They could see the Southern Cross and all the stars of the Centaur. Although there are conflicting reports from ancient Greek sources, most seem to agree that this centaur whose name was Chiron was a wise and benevolent being as opposed to the war-like Sagittarius. Some sources say he was the tutor for Heracles who accidentally wounded his teacher with a poisoned arrow. He begged Zeus to grant the noble creature immortality in the sky. Centaurus is traditionally depicted as carrying Lupus the Wolf to sacrifice on Ara the Altar.

Centaurus contains Alpha and Beta Centauri, the third and tenth brightest stars in the sky. (Note: Some lists name Betelgeuse in Orion as the tenth brightest star, but Betelgeuse is a variable star making its ranking difficult). Alpha Centauri (proper name Rigel Kentaurius) is bright only because it is close and it is the closest star to the sun at 4.3 light years away. Alpha Centauri is a triple star system.

Beta Centauri (proper name Hadar) is a blue-white super giant and in about 4,000 years, the proper motion of Alpha Centauri will carry it close enough to Beta Centauri that they will appear to be a magnificent double star. Since Beta Centauri is about 300 light years away, they will be an optical double. Now the two stars look like two eyes, the right one (Beta) distinctly blue. They are called the 'pointer stars' since they point to the Southern Cross to the west. Some of the Australian aboriginals call them 'The Two Men that once were Lions'. Other aboriginals call them the twins that created the world.

Centaurus also contains Omega Centauri (NGC 5139), the largest and richest globular cluster in the sky. It looks like a 4th magnitude star to those lucky enough to see it, but through even a small telescope the stars resolve into pinpoints of light. The cluster is larger than the full moon. Centaurus also has its very own meteor shower, the alpha Centaurids that are best on the eighth of February.

Centaurus also contains 20 open clusters and several galaxies including Centaurus A (NGC 5128), one of the brightest radio objects in the sky. It also contains a significant portion of our own galaxy, the Milky Way, and the river of stars through Centaurus is an awesome sight on a dark moonless night. Centaurus contains over 100 visible stars (brighter than 5.5 magnitude).

Centaurus is a magnificent sight on a balmy spring night (it reaches culmination on 30 March) or a pleasant fall evening if you live in the Southern hemisphere. Centaurus is truly a jewel of the southern sky.

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