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Transcript
Our installment next month (September) will focus on the constellations of
Cassiopeia, Perseus, Pegasus and Andromeda Thank you. Bob McGovern.
August Skies – Cepheus, Capricornus tiny Delphinus and Sagitta and the
Perseid Meteor Shower.
For the Naked Eye - (for some fascinating mythologies and astronomy facts
simply Google the names found in the text below and check out the sky maps by
Sky & Telescope online at:
http://www.skyandtelescope.com/observing/skychart/ ).
The Constellation Cepheus the King – Cepheus (sē-fē-əs) is the name of a
mythological king of Ethiopia, the son of Belus, king of Egypt and the grandson of
Poseidon. This is not the modern country of Ethiopia south of Egypt in Africa but
was then referred to as a kingdom on the eastern shores of the Mediterranean
(Phoenicia) based in the city of Joppa, now called Jaffa and part of Tel Aviv,
Israel. Cepheus was married to Cassiopeia, was the father of Andromeda and
the father-in-law of Perseus, all interconnected constellations that will be
described in next month’s soap opera section of this newsletter. This is an
ancient constellation representing a king and dates back to at least 400 BC in
Greece. To me, the shape of the brightest stars in this constellation resembles a
lopsided house or, if someone insisted that it represent a primate type figure, I’d
make it a gnome with a big pointy hat and name him Gulcifer. Given the
choices, how would you describe this stellar grouping?
proposed “Gulcifer”
the “crooked house”
Cepheus as accepted
The most well known star in Cepheus is the variable star Delta Cephei (marked
by the arrow pointing at the gnome’s right toe above) first described by John
Goodridke, an 18 year old deaf student in England in 1784. This class of
variable stars, now known as Cepheids, have allowed astronomers to estimate
intergalactic distances since their pulsating periods are related to their absolute
magnitudes. Delta Cephei is a pulsating supergiant star with a period of 5.4
days. Although there are no Messier objects in Cepheus, the area is quite rich
with stars as part of it lies in the Milky Way just above Cygnus.
The Constellation Capricornus the Sea Goat – The plane of our solar system
projected against the stars contains 12 constellations, the ecliptic or the zodiac if
you’re into astrology. Three of these constellations are considered the water
signs and this area of the heavens was described as the sea: Aquarius the water
carrier, Capricornus the sea goat and Pices the fish. These constellations never
get very high in the sky for us here in Rochester and due to the approximate 23
degree tilt of our Earth’s axis, it appears that our sun, on the first day of winter,
can be seen directly overhead at locations of about 23 degrees south latitude – a
circle around the earth known as the Tropic of Capricorn. It is thought that the
“goat” part of Capricornus pertains to the observation that the sun started to
“climb” back towards the north after reaching this constellation, much like a goat
is known for climbing, and the “fish tail” part pertains to it leaving the “wet”
months of winter.
Capricornus is best viewed from a dark location as the stars are quite faint but
once you’ve found it, you can easily recognize it as a part goat facing to the right
with the back end having the tail of a fish. The shape reminds me of the smile of
the Cheshire Cat.
Capricornus is one of the most ancient of constellations and was recorded in the
Babylonian star charts as the “Goat Fish” about 3,000 years ago.
There is a great deal of mythology
around Capricornus and one
describes the origin from the god
Pan. The worship of Pan spread
throughout Greece from Arcadia
around the time of the battle of
Marathon. He was the god of the
forest, pastures, shepherds,
mountains and every place natural.
He protected flocks and had a great
time dancing around and playing
his flute. Pan was also noted for
his sexual powers and, through
trickery, seduced Selene, goddess
of the moon.
One myth tells of Pan being
attacked by a monster and being
forced to dive into the Nile to
escape. The half of Pan that
stayed above the water retained the
features of a goat and those under
the water turned into a fish. There
is lots of fun reading about Pan!
Neptune was discovered in Capricornus by Johann Galle in 1846 although it was
observed by Galileo in 1613 and his records showed that he even noticed that it
had moved somewhat in later observations. Neptune was around magnitude 8
and did not show a disc in his equipment. Johann Galle, however, made his
observations of selected areas based on mathematical calculations of his own
and by others using Newton’s laws of gravitation and how they affected the
motion of Uranus. Since its discovery in 1864, Neptune is once again in the
constellation of Capricornus on its 163 year trip around the sun. It is currently
shining at magnitude 8 at a distance of 29 astronomical units from the sun and is
about 3 degrees east of brilliant Jupiter at mid month.
The Constellation of Delphinus the Dolphin This is just a tiny constellation but an ancient one just
the same. You can locate this pretty star pattern by
looking for the little quadrilateral just to the east of a line
drawn between the bright stars Deneb and Altair in the
“summer triangle”. The 4 brighter stars in the head also
form the asterism commonly called Job’s Coffin (marked
in blue) for reasons lost in history. A few fainter stars
form the body and tail of the dolphin. Delphinus was a
messenger of Poseidon, god of the sea. Poseidon sent
the dolphin with messages to one of the sea nymphs to
become his wife who found it impossible to disappoint
this cute animal. For accomplishing this, Poseidon gave
the dolphin immortality in the heavens.
The Constellation of Sagitta the Arrow Extend this line to Deneb
extend this line to Vega
The blue stars and connecting lines define the two tiny constellations of
Delphinus and Sagitta. Sagitta lies within the boundaries of the “summer
triangle” asterism and is imbedded in the Milky Way so sweeping through this
area with your binoculars of wide field telescope is well worth the effort. In dark
skies, Sagitta is formed by 4 stars and was told by the ancient Greeks to be the
arrow that Hercules used to kill Aquila the eagle. If you look at any star chart,
however, the arrow is above the eagle and heading in the wrong direction! It was
a clear miss of the eagle but appears headed towards the belly of Vulpecula the
fox (a very faint constellation within the “summer triangle”). There are other
stories that associate Sagitta as the arrow of Cupid.
The Perseid Meteor Shower – I have great memories from my childhood of
lying in a field across the road from the home where I grew up in (very) rural
Pennsylvania (Bear Hollow) watching the Perseid meteor showers every August.
Just lying there wrapped up in a blanket and listening to the crickets in pitch
blackness until I fell asleep was something that would paralyze me now but was
certainly magical then.
The source of the Perseid meteor shower is actually debris from the comet SwiftTuttle. Every year, the earth passes through the debris stream left by the comet
and the earth's atmosphere incinerates the particles into the glowing embers
called meteors or “falling stars”. The shower peaks early afternoon on the 12th,
so the morning of the 12th (midnight to dawn) is the best time to watch although
quite a few should be visible a few nights before and after this date. The meteors
from this shower appear to radiate from the constellation Perseus which is
located low in the NE sky. It’s important then to find a dark location with a good
view to the NE and enjoy the show. The bright moon present this year will
obscure the fainter ones but you should still see quite a few. Like most celestial
events, they are best viewed from a dark, moonless location. Maybe next year
the moon will cooperate.
The More Prominent Planets –
Jupiter - Jupiter is absolutely brilliant at magnitude minus 3 low in the SE in the
constellation of Capricornus at around 10 pm. It reaches it highest point above
the horizon around 3 am at mid month and still, as of August 10, shows a faint
scar from the asteroid or comet impact that occurred last month.
The Moon and the Moon and Venus- This month the full moon is on August
6th and is called the “Full Sturgeon Moon” by some Native American tribes
around the Great Lakes as it was the prime time to fish for sturgeon. It was also
called the “Green Corn Moon” or the “Grain Moon”. A few tribes called it the “Full
Red Moon” because of its color when rising through the warm summer haze.
The waning crescent moon will make a beautiful early morning pair with the
“morning star” Venus on the 17th and 18th of the month with Venus at a brilliant
magnitude of minus 4.