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Centaurus is one of several constellations that deal with the
Labours of Heracles.
In the Fourth Labour, Heracles' assignment was to bring back a rampaging
wild boar that was bringing death and destruction to the inhabitants of
the northern part of the Peloponnesian peninsula. On his way, he stops
to visit a friend of his, a Centaur named Pholus.
Centaurs were featured in a number of Greek myths, but by and large
remained on the periphery of Greek fable.
Gathering up huge boulders, ripping out trees to use as clubs, and
arming themselves with axes, the Centaurs advance on the dinner party.
Pholus takes fright, so the battle is left to Heracles. After repulsing
a number of Centaurs single-handedly, Heracles then chases the rest of
them to the cave of their king, Cheiron.
Heracles shoots an arrow at one fleeing Centaur (Elatus by name), but it
passes through his arm and strikes Cheiron on the knee. You may recall that
Heracles' arrows were all dipped in poison, so each was fatal, no matter
how slight the wound. Cheiron was a great friend of Heracles, and our
hero is devastated. He tries to assist Cheiron, but there is nothing to
be done.
Cheiron was immortal, so the poison couldn't kill him, only cause great
pain that would last through eternity. He descends to the depths of his
cave, his screams of agony echoing throughout the cavernous walls.
Eventually Prometheus takes pity on the long-suffering king of the
Centaurs, and offers to take over Cheiron's immortality, if Zeus would
agree. Zeus does agree, so Cheiron's agony finally comes to an end,
and Zeus places the great king of the Centaurs in the heavens.
Back to the previous battle. The Centaur Pholus looks over the dead and
dying and wonders how Heracles' arrows could be so fatal. He plucks one
arrow out of a body and looks at it, but it slips through his fingers and
strikes him on the foot, killing him instantly.
Heracles hears of the tragedy and returns to bury his friend, at the
foot of the mountain that bears his name: Mt Pholoe.
These half-men half-horse figures were also transformed at times to
half-man half-goat. Many rituals are known to have involved dressing as
one of these half-beasts, rituals which may date back to Neolithic times.
Centaurus is one of the largest constellations
with a clearly discernible asterism: the huge form faces east, with a
sword waving menacingly toward Lupus the Wolf on the west.
The constellation has an almost complete list of Bayer stars except for omega, which isn't a
star, but a well known globular cluster, NGC 5139 (see below).
The front hooves (or feet, if you wish) are formed by two bright stars:
alpha and beta Centauri, known also by the Arabian names of Wazn and Hadar.
Alpha Centauri is best known by the name "Rigil Kentaurus", or the
Centaur's foot. This is a triple system, three stars which are the closest
to our own Sun.
The closest star is actually alphaC, known as Proxima
Centauri. This is a red dwarf of visual magnitude 11.01 and distance
4.221 light years.
Beta Centauri is a difficult double because of the primary's brightness compared to the companion: 0.58, 3.95; PA 251º, separation 1.3". The orbit has not been calculated, but is thought to be at least several hundred years.
Gamma Centauri is a visual double of two nearly identical stars, with orbit of 84.5 years: 2.9, 2.9. The 2000.0 values are a PA of 347º and separation 1.0".
Eta Centauri is a binary with very faint companion: 2.3, 13; PA
270º, separation 5.6".
Kappa Centauri also has a faint companion: 3.1, 11; PA 82º,
separation 3.9"
Many more binaries are found in this enormous constellation. Check the Binocular link below.
The prototype of this kind of variable is UV Ceti, which has been known
to change 3.5 magnitudes within seven seconds!
The cluster is estimated to be from 15000 to 25000 light years away, and
may be comprised of over a million stars.
For a closer appreciation of Centaurus, visit the Binocular Section.
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© Richard Dibon-Smith.