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Did it start as a bang!
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The Expanding Universe
A. The Big Bang Theory:
Idea that all matter began in
an infinitely small point and
exploded out in all
directions
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Galaxies: _____________________
_____________________________
______________________________Billions of
stars, dust,
and gas held
together by
gravity
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UNIVERSE
Let’s start out big and work our way down
VIRGO SUPER CLUSTER
LOCAL GROUP
GALAXY: BILLIONS OF
STARS, DUST AND GAS HELD
TOGETHER BY GRAVITY
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• ________________ was an astronomer in the 1920s who
gathered many pictures of galaxies
Who knew?
• noticed they all didn’t look alike
• decided to classify them by the way
they looked into 3 types
• “E” or _____________________
• “S” or _____________________
• “SB” or ____________________
Spiral
Barred Spiral
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Galaxies
• Galaxies are grouped
together in clusters.
• The cluster the Milky
Way belongs to is called
the Local Group.
• Three types of
galaxies:
• Cluster of galaxies
Where do we live? Earth’s
Galaxy—and Others
• Galaxies are
grouped together
in clusters.
• The cluster the Milky
Way belongs to is
called the Local
Group.
• Cluster of galaxies
Spiral Galaxies
• Spiral Galaxies: Circular
galaxies that have
arms curve outward
from a central hub.
–Arms are made
up of stars and
dust
• Two spiral galaxies!!
Elliptical GalaxiesMost common type of galaxy; large three-dimensional
football shaped galaxies.
-Contain mostly older and dimmer stars.Vary in shape from completely round to extremely
elongated ovals. Unlike spiral galaxies
No bright nucleus at their center. Elliptical galaxies are
represented by the letter E
Divided into seven subgroups according to their shape.
These subgroups are labeled E0 to E7. E0 galaxies
nearly circular in shape while E7 galaxies are
extremely elongated or stretched out.
Irregular Galaxies
• Come in many different
shapes and are smaller
and less common
• Irregular Galaxies - No
regular shape, includes
nebulas, with no central
bulge or spiral arms.
Earth’s Galaxy
• Galaxy: A large group of
stars, gas, and dust held
together by gravity.
• Milky Way: Our galaxy
which contains about 200
billion stars and many
nebulas
• Spiral Galaxies
The Milky Way Galaxy• The Milky Way is the galaxy that contains our Solar
System which is just one of the several galaxies of the
universe.
• . This name derives from its appearance as a dim
"milky" glowing band arching across the night sky, in
which the naked eye cannot distinguish individual stars.
• 100,000 light years in diameter
• Our sun orbits the center of the galaxy once every 240
million years
• A barred spiral galaxy
• Contains over 200 billion stars
• Its where we live!!!!!
Solar System
Our star (Sun), the planets, many
moons, and other small bodies that
ALL travel around the Sun
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What do we see in the sky?• The stars move in the sky but not
with respect to each other
• The planets (or “wanderers”) move differently from stars
– They move with respect to the stars
– They exhibit strange retrograde motion
• What does all this mean?
• How can we explain these movements?
• What does the universe look like?
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The Great Debate!
• Heraclides (330 B.C.) developed
the first Solar System model,
beginning of the geocentric versus
heliocentric debate
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Geocentric (Ptolemaic) System
• The theory (in Greek, geo means
earth), which maintained that
Earth was the center of the
universe, usually referring to the
system of Claudius Ptolemy.
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Geocentric
(Ptolemaic) System
• The accepted model for
1400 years
• The earth is at the center
The Sun, stars, and
planets on their spheres
revolve around the earth: explains daily
movement
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Geocentric (Ptolemaic) System cont’…
• To account for unusual planetary
motion epicycles were introduced
• Fit the Greek model of heavenly
perfection – spheres are the perfect
shape, circular the perfect motion
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Heliocentric (Copernican) System
• The word "helios" in
Greek means "sun."
Heliocentric means that
the sun is at the center.
A heliocentric system is
one in which the planets
revolve around a fixed
sun.
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Helio- continued
• Thus Mercury, Venus, the Earth,
Mars, Jupiter and Saturn all
revolve around the sun. The moon
is the only celestial sphere in this
system which revolves around the
earth, and, together with it, around
the sun.
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Heliocentric (Copernican) System
• Sun at center
(heliocentric)
• Uniform, circular motion
–No epicycles (almost)
• Moon orbited the earth,
the earth orbited the sun
as another planet
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Heliocentric (Copernican) System
• Planets and stars still on
fixed spheres, stars don’t
move
• The daily motion of the
stars results from the
Earth’s spin
• The annual motion of the
stars results from the
Earth’s orbit
Our Solar System
Our solar system is made up of:
Sun
Nine planets
Their moons
Asteroids
Comets
Meteoros
Inner Planets
The inner four rocky / Terrestrial planets. These planets have hard rock crusts, and dense rock and metal cores are:
Mercury
Venus
Earth
Mars
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Mercury• Mercury is the closest planet to the Sun.
• Mercury rotates the Sun in only 88 days.
• Mercury rotates very slowly on its axis with
one day taking 58 Earth days.
• Mercury barely has any atmosphere, but
does have glaciers.
• Called a morning star. This is because
Mercury shines brightly in the early morning
just before the sun rises. It has also been
called an evening star for the same reason.
Mercury is often visible for a brief period of
time just after the Sun sets.
Venus
Sister planet to Earth Size and structure is VERY similar to Earth, often called "Earth's Twin"
Has no moons or rings
Hot, thick atmosphere
Brightest object in sky besides sun and moon (looks like bright star)
Covered with craters, volcanoes, and mountains
Earth
Third planet from sun
Only planet known to have life and liquid water
Atmosphere composed of composed of Nitrogen (78%), Oxygen (21%), and other gases (1%).
Mars
Fourth planet from sun
Appears as bright reddish color in the night sky Called "the Red Planet" because it surface is covered with iron oxide- RUST! Proves that Mars once had free oxygen molecules in its atmosphere.
Surface features volcanoes and huge dust storms
Has 2 moons: Phobos and Deimos
Outer Planets
A gas giant (sometimes also known as a jovian planet after the planet Jupiter, or giant planet) is a massive planet with a thick atmosphere of hydrogen and helium
Jupiter
Saturn
Uranus
Neptune
Jupiter
Largest planet in solar system
Brightest planet in sky
60+ moons, 5 visible from Earth
Strong magnetic field
Giant red spot
Rings have 3 parts: Halo Ring, Main Ring, Gossamer Ring
Saturn 6th planet from sun
Seven thin, flat rings not solid but made up of particles of ice, dust and rocks
31 moons
Largest moon, Titan,
Easily visible in the night sky
A lightweight planet and it spins so fast
Voyager explored Saturn and its rings.
Uranus 7th planet from sun
Has a faint ring system
27 known moons
Covered with clouds
Sits and spins on its side with the north and south poles sticking out the sides.
Neptune 8th planet from sun
Discovered through math
7 known moons
Triton largest moon
Storm called the "Great Dark Spot" because it appears as a dark oval shape on the surface of the planet.
Great Dark Spot thought to be a hole, similar to the hole in the ozone layer on Earth
Pluto our dwarf
Pluto, the outermost planet, is a small, icy "dwarf planet“ it is smaller than the Earth's Moon.
Pluto
9th planet from sun (usually)
Never visited by spacecraft
Orbits very slowly
Moon, Charon, is very close to Pluto and about the same size
Comet- chunks of ice and dust
• Has an elliptical orbit around Sun
• Has a head (nucleus and coma) and
tail.
• Tail always points away from sun.
Asteroids-
Larger chunks of rock
Vary in size and shape
In Asteroid Belt between
Mars and Jupiter
Revolve around sun in 3-6
years
Asteroids: Illustrate /draw
Meteoroids- smaller chunks of rock and dust in space.
1. randomly move about space ; no specific orbit
2. come from remains of comets and asteroids
• Meteor- a meteoroid that burns in the atmosphere- produces a streak of light.
nickname: “Shooting star”
•MeteoriTe- a meteoroid that doesn’t burn up in the Earth’s atmosphere. It Touches Earth.