'Astronomy and our World Today'
Textbook - Modules 1-13
Author: Professor Avon
Chapter 4: The Gas Giants
Flying further to the reaches of outer space we find the Gas Giants! These planets are rather unique and beautiful. Jupiter Saturn Uranus and Neptune are the larger members of our Solar System, Jupiter being the largest. They are known as Gas Giants because that is basically what they are! Big Giant Humongous... large balls of gas. These Four Planets are made mostly of hydrogen
and helium and thicker layer of metallic hydrogen. Even though they are giant balls of gas they still have a giant solid cores that are 7 times larger then earth. These planets are often called "Jovians" because Saturn Uranus and Neptune are thought to be small version so Jupiter and Jove is a Latin word meaning Jupiter.
Jupiter
Mythology: Jupiter was worshipped as an important God in many Cultures. He usually went by different names however. For Example: Rome: Jupiter was one of the most important Roman gods, he usually changed with need. In the early Roman Era he appeared as the god of agriculture who controlled the sun and the moonlight, win rain storms thunder lightening ect.
Greek: He was named Zeus in Greek Mythology. He overthrew his father Cronus and became the ruler of the gods on mount Olympus. He was also known as a rain God and God of the Sky is depicted with a Lightening bolt in his hand.
India: He was known as Guru or Brihaspati in Hindu Mythology. He was
thought to be a teacher or counselor of the rulers of heaven (The
Devas). He is highly regarded as the sun of Angiras and is renowned as
an intelligent and knowledgably god by the Hindus.
Ammon: He is one of the Chief Egyptian gods and was shown as a picture of a Ram's head.
Facts: Jupiter is the largest planet in our solar system. It is visible
in our nights sky with the naked eye (yes quite a treat!). It is the
fifth planet from the sun and about 318 times larger then Earth. It is
twice larger then ALL the other planets combined. It has an equator
that is 11 times wider then earths. Jupiter has the most circular orbit
out of all the planets however because it is so far away, it takes 12
years to complete one rotation around the sun. In spite of its slow
rotation around the sun it's rotation results in a day that is only 10
earth hours long.
Jupiter’s most unique feature and one you will probably hear much about
is "The Great Red Spot". This spot is a huge storm that measures 12,000
by 25, 000km. That is big enough to hold 2 earths beside one another.
Even though Jupiter’s cloud patters change with in the hours or days
like here on Earth, The Spot has lasted over 300 years.
Many people do not know this but Jupiter does have rings like Saturn;
However they are fainter and smaller. They are most likely made up of
very small grains of rock and other stray materials not ice like
Saturn. This brings us to her moons! As of last count Jupiter has 63
Satellites orbiting outside its rings (last counted May 2005). In
addition to the four inner moons the next four are the largest and
referred to as Galilean moons because Galileo the Astronomer first seen
them in 1610. The four moons names are Io, Europa, Ganymede, and
Callisto.
Saturn
Mythology: Saturn is the Roman god of agriculture and in named Kronos
by Greek Mythology. He ruled the heavens in its 'golden age' he brought
the world social order and the arts. He planted the seeds of
civilization. Saturn was dethroned by his sons Jupiter, Neptune and Dis.
Facts: Saturn is the 6th planet from the sun. It is smaller then
Jupiter but its rings are a vision to behold. It is the second largest
planet in our solar system it is extremely less Massive then Jupiter.
It is only about 95 times larger then Earth's mass. Saturn's poles are
flattened because of its very fast rotation of less then 11 hours
(which means 1 day = 11 hours on Saturn). In spite of its quick
rotations it takes 29.5 years to complete one orbit around the Sun.
Saturn’s rings are made of mostly water ice, or even possibly rocks
coated by ice. The ring's vary in size with some containing particles
no larger then pea pebbles or dust and others with boulder sized or
even giant rock's that are over several meters wide. It is estimated
that there could be objects as large as a kilometer in diameter. The
rings are around 250 000km wide. They are not very thing a few hundred
meters thick.
A recent look at the moons or satellites around Saturn reveals 47
known. They tend to come and go as they please it seems. Saturn’s
largest moon is known as Phoebe it is dark with a highly inclined
orbit. Saturn's has a few other larger moons like Jupiter’s Galilean
moons. For example a few are named, Pan, Atlas, Prometheus, Pandora,
Hyperion, Mimas and Tethys.
Uranus:
Mythology: Uranus is the Latin version of Ouranos (Greek for sky). In
Greek Mythology Uranus is the Son and Husband of Gaia (mother earth).
These two gods are ancestors of Jupiter (Zeus). In Roman mythology he
is equal too Coelus.
Uranus was a key part in the Olympian Creation myth. Uranus came every
night to cover the earth and mate with Gaia, Mother Earth. However he
hated the children they had and put Gaia's youngest in to prison
(Tartarus). These children were Hecatonchires, and cyclopes. Gaia was
sad and asked her Sons Cronus and Uranus to casturate their father with
a flint sickle she created. Cronus took the challenge and ambushed his
father and castrated him. Uranus's remains spilled to earth and grew as
Gigantes, the three avenging Furies, the Erinyes and Melia the ash
nymphs. It is also said that the parts of him that fell in the sea grew
Aphrodite
Facts: Uranus is the 7th planet from the sun. It is the 3rd largest
planet in our solar system. It takes 84 years to orbit our sun. It
rotates in 17.5 earth hours. Uranus's axes unusually likes on the same
plane as the solar System (as if it was knocked over). This planet is
quite 'plane' in comparison to Jupiter’s mass and Saturn’s rings. It
too has a faint ring of rings. It has around 27 satellites but only 5
are of substantial size to be called moons. Miranda, Ariel, Umbriel,
Titania and Oberon.
Neptune:
Mytholgoy: Neptune is the Roman version of the Greek god Poseidon. He
is one of the three sons of Kronos. His domain became the sea when the
world was divided between Zeus Hades and himself. Poseidon was given
complete control of the water element.
Facts: The Eight planet on our list and the 8th farthest from the sun.
Neptune is the farthest of all four gas giants. It is not much smaller
then Uranus but is denser. Like all the other gas giants Neptune has a
very fast rotation and takes 16 Earth hours it has a slow orbit and
takes 164 earth days.
Chapter 5: What is a Star?
Now what kind of SILLY question is that you ask? Stars are those bright
shinny things made of gas that are up in the sky. Our own sun just
happens to be a star. There are billions of them in our universe. There
is much more to stars then the points of light we see. It takes
millions or even billions of years for that light to reach earth. So
essentially when we gaze at the stars we are seeing ancient objects.
That is unless your me and can see in to the future.
Chapter 6: What is a Galaxy?
So a galaxy- that is a system of about 100 billion stars. Not only
stars but also a collection of gas dust and stars held together by
shared gravitation. We are a member of the Milky Way Galaxy. We can
view billions of Galaxies currently from Earth. Our sister Galaxy is
called Andromeda and is very beautiful on a dark night. I suggest
everyone go out and see it as soon as you can. There are 3 types of
galaxies, elliptical spiral and irregular. We live in a spiral galaxy.
Chapter 7: The Sun
The crowning glory and overlady of our solar system is the Sun. For
millions of years it has been worshiped as a god: The giver of life and
light. With out it we wouldn't be here to talk about it! It allows
plants to grow and along with some other basic elements keeps our
planet on track.
Unlike a planet the sun is made up of a multitude of layers.
The Core: It is incredibly dense, most would think because of its
density it would be a solid however it is so hot, 15 million Kelvin’s
(27 million degrees Fahrenheit) to be exact, the core is in a gaseous
state. The core is the 'heart' of our sun. Here fusion reactions
produce energy called gamma rays and neutrinos. Gamma rays are photons
with a very high energy and frequency. The rays are absorbed and then
re-emitted by atoms on their way out of the sun. The core contains 40%
of the suns mass in 10% of its volume.
Solar Envelope: It is broken in to two areas, the radioactive envelop
and the convective envelope. This layer is not as dense as the core and
its temperature is around 4 million Kelvin’s or 7 million degrees
Fahrenheit. The Envelop puts pressure on the core and maintains the
temperature for fusion to take place. The hotter the gas is the more
transparent it is, so this area of the sun is more opaque then the
core. This causes it to be less efficient for energy to move by
radiation and heat builds up on the radioactive area, this is how the
convection zone is created. It is huge cells of moving gas several
hundred kilometres in diameter.
Photosphere: This is where our sun light is emitted. This area is a
layer of low pressure gasses just outside the envelope. It is only a
few hundred kilometers thick and about 6000 degrees Kelvin. You can
find out the composition, temperature, and pressure by analyzing the
colour spectrum of sunlight. A little side fact, helium was discovered
by Mr. William Ramsey. He was analyzing the spectrum of sunlight when
he found features that were not present in anything on earth. He named
it helium after the Greek God of the Sun Helios.
Chromosphere: After the photosphere the layers of the sun gradually
become hotter again. In an eclipse you can see this layer on occasion
as the red circle outside the sun. Its red colour is caused by the
amount of Hydrogen. The other layers get cooler as they get farther
away from the core; however this layer is 7000k. Temperature increases
through the Carona.
Corona: The Carona is the farthest layer of the sun. It is only visible
during an eclipse. It is very low density because it is a cloud of
plasma with a high transparency unlike the inner layers. The white
Carona is a million times 'less' bright then the inner layers of the
sun but many, many times larger. We find this layer to be hotter then
the inner layers with a temperature of 1 million degrees Kelvin or 2
million degrees Fahrenheit as an average but some areas can become 3
million degrees Kelvin." Moving back to her desk she got another drink
of water.
Chapter 8: The Moon
Wizard Mythology: If I remember correctly even Muggle’s say the moon is
made out of cheese. It may be a jest for them but here in the Wizarding
world it is true. A few hundred or more years back a wizard wanted to
fly to the moon. He tried many spells and they never worked. One day he
got so angry he used a rare and forbidden magic that launched him in to
outer space and on to the moon. He wasn't sure what to do so as he fell
he turned the spot he was going to land in to cheese so it wouldn't
hurt. At least that is the 'legend'. It is just on the border between
the lighted and the dark side of the moon.
Facts: Below I have an image of the moon's phases. This is one
'lunation' or lunar month. It has an elliptical orbit that varies its
distance from Earth. The Moons "near" side faces the earth more then
the "far" side. An effect called "Libration" is the reason for the
Moon's different angles at is orbits us. It is caused by the moons
partially titled axis compared to its orbital plane and because the
speed and orbit vary.
Phases:
New Moon: The Moon's dark side is facing the Earth. The Moon is not visible (except during a solar eclipse).
Waxing Crescent: The moon appears to be less then half light up in direct sunlight.
First Quarter: Half of the Moon appears to be lit by direct sunlight.
Waxing Gibbous: The Moon appears to be more than half but not fully lit up by direct sunlight.
----------------- All the phases above the light appears to be INCREASING -----------------
Full Moon: The Moon's fully lit up side is facing the Earth. The Moon appears to be completely illuminated by direct sunlight.
Waning Gibbous: The Moon appears to be more than one-half but not fully
lit up by direct sunlight. (The opposite side of Waxing Gibbous)
Last Quarter: Half of the Moon appears to be illuminated by direct sunlight. (The Opposite side of First Quarter)
Waning Crescent: The Moon appears less than one-half illuminated by direct sunlight. (Opposite side of Waxing Crescent)
Thu Dec 11, 2008 12:14 pm