HerculesHercules
Particulars:
General:
This northern constellation is not very conspicious but the
fifth largest in the sky. The northern boundary runs close to
DECL=50 degrees, the southern streches with DECL=4 degrees nearly
down to the celestial equator. The west-east extention starts at
RA=15h 50m and nearly reaches RA=19h.
The four stars epsilon Her, zeta Her, eta Her and pi
Her form the asterism Keystone.
Hercules seems to be kneeling on the head of Draco. His
outstreched hand is holding a bow and the arrow Sagitta is flying
towards the two birds, the Eagle, Aquila and the Swan, Cygnus.
The greek word for the complete form is Kornephoros.
Stars and other objects
The leading star alpha Her, called Ras Algethi
(arab.: kneeler's head), is a red supergiant (spectraltype
M5Ib-II). Its brightness varies erratically from 3.1 mag to 3.9
mag. A small telescope reveals a second star of 5.39 mag
(physically not related to the other). This 'companion' is a
binary consisting of a G5 giant and a F2 main sequencec star (not
resolvable by amateur scopes).
The brightness of the variable star S Her varies every 307
days from 5.9 mag to 13.6 mag. It belongs to the same class of
variable stars as R Ser.
The varibale star SZ Her is a eclipsing binary. Every 16
hour the fainter component dims the brighter from 10.2 mag down
to 12th mag. The eclipse has a duration of about 90-100 minutes.
The double zeta Her (a 10157) has a period of 34 years.
An easy object for small telescopes is kappa Her. The two
stars are a G8III of 5.00 mag and a K1III of 6.25 mag.
Also resolvable in small scopes is the pair rho Her, an A0
main sequence star of 5.47 mag and a B9.5 III star of 4.52 mag.
The binary u Her consists of a B1.5Vp and a B5III star.
The system appears to the naked eye as a star of 4.82 mag.
An attractive pair to observe with small telescopes is 95 Her;
two stars of 5th mag shining in a golden and silver light.
One of the most beautiful globular clusters in the sky is M13,
the famous Hercules Cluster. To the naked eye it
is visible as a star of 4th mag. In smaller telescopes it appears
as a misty patch being more dense towards the center. Large
scopes reveal a nearly perfect sphere of stars.
Although nearly a magnitude fainter M92 is still an
interesting object for smaller scopes.
NGC 6229 is a faint globular cluster - compared to the
other two. Its brightness is just of 10th mag.
The planetary nebula NGC 6210 shows a quite bright inner
ring and a faint outer ring. The apparent dimension of the latter
is 20''x43''.
The next object is not visible with amateur telescopes: Hercules
X1 together with Cygnus X1 is probabaly the most
studied X-ray source. The spectrum of Hercules X1 shows a
periodicity of tau=1.2378 sec; within this interval the
star finishes one revolution around itself. This is a typical
value for pulsars - fast rotating neutron stars. A second
periodicity has been discovered: each 1.7 days the signals stop.
So obviously Hercules X1 is part of a double star. In
September 1970 the primary star could be located: its HZ Her.
This system lies in a distance of about 20000 lightyears from us.
Its mass of Hercules X1 has been determined to be 0.9
+/- 0.4 solar masses.
From May, 19th, to June 19th, the meteor shower Tau Herculids
is active. On June, 9th, the maximum occurs with about 4 meteors.
See Gary Kronk's database of meteor showers for details.
Mythological Background:
In the mythology of the ancient Greeks Hercules has been the
son of Godfather Zeus and the Alkmene, the wife of Amphitryon.
Zeus made Alkmene believe thar he was Amphitryon.
Of course, Hera, the wife of Zeus, was not very pleased by this;
somehow she managed that Eurystheus was the first born son of
Alkmene. This son gave this half brother twelve tasks to solve:
to strangle the Lion of Nemea,
to kill the Hydra,
to catch the hind of Diana,
to kill or chase the Stymphalion Birds,
to bring the boar of Erymanthes to Mykene alive,
to defeat the bull of Kreta,
to clean the Augias stable,
to tame the maneating horses of king Diomedes,
to get the arms of the Hippolyta,
to get the cows of the giant Geryon,
to pick the apples in the garden of the Hesperides (well, it was Atlas who picked them while Hercules carried the heaven),
to get Zeberus, the three-headed dog of the Hades (hell)
(Ovid, Metamorphoses, IX,2).
Because all this has to be done because Hera wishes so (to
perish Hercules, not to make him famous); yet his greek name was
"Heracles", meaning "the man becoming famous
through Hera".
At last the gods accepted him as one of them and gave him Hebe as
wife.
