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Astronomy = the study of space
• The big bang theory proposes that about 14 billion
years ago the entire universe was in a bubble smaller
than the head of a pin. It was hotter and denser than
anything we can imagine…then it EXPLODED and the
universe was born!!! Time, space and matter all
started with the big bang. The universe grew from
being smaller than an atom to larger than a galaxy.
The universe continues to expand.
• The Nebular theory tells us how solar
systems and stars are created.
Gaseous clouds (nebulae) slowly
rotate, gradually collapse & flatten
due to gravity and eventually form
stars and planets.
• No one knows the size or shape of
the universe but there are billions of
galaxies spread throughout the
• Gravity or gravitational forces are
forces of attraction.
• Every object that has mass exerts a
gravitational force on every other
•Planetary Gravity –
the Sun’s
gravitational pull
keeps the planets
orbiting the sun.
•The motion of the
moon is affected by
the earth and the
• The amount of gravitational pull depends
on the amount of mass & the distance
between the two objects. Mass is the
amount of matter and object has. Gravity
is a force caused by mass. Weight is a
measure of how much force is applied due
to mass. Distance also plays a role in the
amount of gravity: if the distance between
objects is increases then gravity
decreases, and conversely if the distance
between the objects is decreases then the
gravity will increase.
• Gravity gives objects weight. No one
knows the mechanism by which gravity
• The universe is made up of two things –
matter and energy.
• Matter examples – planets and stars.
• Energy examples – light and heat
• The universe is made up of galaxies.
There are 2,000,000,000,000,000,000
stars in the universe and each of these
stars makes up a galaxies.
• The universe has a diameter of 150 billion
light years! The universe is more than
13.7 billion years old!
Solar System
Country Home
• Universe
• A galaxy is a group of millions of stars relatively near each
other. Most stars seem to be in one or another galaxy.
Earth’s own star - the Sun – is in the Milky Way Galaxy.
Small galaxies have about 10 million stars – Big galaxies
have a trillion stars.
• There are three types of galaxies: spiral, elliptical, and
• Spiral Galaxies have a bulge, disk and halo. The bulge is
a round structure in the center. The disk is made up of
dust and gas. The disk forms “arms” of our galaxy. Our
galaxy the Milky Way is located in an arm of our galaxy.
Elliptical galaxies are shaped like an elongated
sphere. These galaxies are older and therefore have very
little dust or gas.
Irregular galaxies have no shape.
• turns like a pinwheel.
• This the type of our galaxies shape
“The Milky Way”
• Our star, the sun, is located on the
arm and the planets travel around
the sun
• Sun takes 250 million years to make
a complete trip
• Arms Are Stars
• Contains Gas and Dust
• Ellipse or Sphere shape (Oval)
• Thought to contain older stars.
• Contains almost no gas or dust
• no definite shape
• Contains lots of dust and
fewer stars
Picture of the Galaxies
Spiral Galaxy
Irregular Galaxy
• Comets are sometimes called “dirty snowballs”
because they are a mixture of ice and dust, and so
they look like dirty snowballs. The ices contained
by comets include: water, methane, ammonia and
carbon dioxide. The ices sublimate off the nucleus
when the comet nears the sun. A dust tail – which
is the part of the comet easiest to see – is made of
dust particles driven off the nucleus by escaping
gases. As the sun vaporizes the gases a coma is
formed which is a cloud around the nucleus.
• Comets are leftovers from the formation of the
Meteoroids, Meteor and Meteorite
• Meteors or meteorites are bits of rock (like granite)
and ice – from out in space that get pulled in by
Earth’s gravity and fall through the atmosphere
and sometimes land on earth’s surface. Many
meteors are from comet pieces.
• Meteors are sometimes called “shooting stars” but
they are not stars. They glow in the sky like stars
because when they hit the earth’s atmosphere the
friction of the rock rubbing against the atmosphere
causes heat and light – and look like a fire.
• Most meteors are tiny, the size of pebbles, and
most fall in the ocean.
• Remember!
• Meteor – flash of light
• Meteorite – space rock that hits
earth’s surface
• Meteoroid – piece of an interplanetary matter smaller than a
• Asteroids are generally larger chunks of rock
that come from the asteroid belt between Mars
and Jupiter.
• Asteroids are metallic, rocky bodies without
atmosphere that orbit the Sun, but are too small
to be classified as planets.
• Asteroids are thought to be primordial material
which has been prevented from forming planets
– accretion.
• Known asteroids can range in size from 1000
km to the size of pebbles.
• The solar system is made up of all
the planets that orbit our sun. The
solar system also consists of
moons, comets, asteroids, minor
planets dust and gases.
• Everything in the solar system orbits
(revolves) around the sun. The sun
contains 98% of all the matter (mass)
in the solar system. The sun is so
massive it has more gravitational pull
that any other objects in the solar
system & attracts all other objects to
it. These objects are moving quickly
away from the sun and so are not
pulled into the sun.
• The sun is the center, then Mercury,
Venus, Earth, Mars, Jupiter, Saturn,
Uranus, and finally Neptune. There is
a band of asteroids between Mars
and Jupiter. The Kuiper Belt exists
beyond Pluto – most all items in the
Kuiper Belt are comets.
• The Oort cloud is even farther out and
consists of comets buzzing around in
random directions.
Inner Planets - Terrestrial Planets
• Mercury, Venus, Earth and Mars
• Closest to the Sun
• Have Rocky Crust
• Small in Size
• Dense in mantle and core
• Temperature depends on the sun
Outer Planets - Gas Giants
Jupiter, Saturn, Uranus and Neptune
Farthest from the Sun
Made of Mainly of Gases
Small Solid Core
Most have Rings Around Them
Most have Many Moons
Most have much more mass that gravity
pull objects in close
Geocentric Theory
Geocentric – Geo = earth, centric = center
• The geocentric model states that
the earth is the center of the solar
system and universe. The Catholic
Church supported this model
because the church taught that God
put earth at the center of the solar
system/universe. Aristotle and
Ptolemy were two supporters of
geo-centricity. The idea that the
earth was moving seemed silly,
because if the earth was moving we
should be able to feel the
•The order of the planets in the Geocentric model is: Earth, moon,
Mercury, Venus, Sun, Mars, Jupiter, Saturn, and the stars.
Heliocentric Theory
Heliocentric – Helio = sun, centric = center
• The heliocentric model states that the
sun is the center of the solar system
and the earth and other planets revolve
around the sun. The geocentric model
had been accepted for 1000 years. A
scientist named Copernicus proposed
that the sun was the center of the solar
system. The church felt as though this
idea went against the teaching of the
church. Galileo wrote a book that
supported Copernican ideas –later he
was arrested and found guilty of heresy
and sentenced to house arrest for the
remainder of his life. Galileo was
pardoned 350 years after his death.
What you see as moon light is really
light from the sun reflecting on the moon’s
surface. Areas where sunlight doesn’t
reach look dark. Areas on the surface
move into and out of sunlight.
The moon’s position in its monthly orbit
determines how it appears form earth.
• Phases of the Moon –
• 1st Week – Moon starts to Wax (starts looking larger)
• New Moon – unlit portion of moon faces earth, the
moon looks dark
• Waxing Crescent – A small portion of moon can be
• 2nd Week
• 1st Quarter – 50% of the near side is in sunlight and
can be seen
• Waxing Gibbous – near side of moon is more than
50% lit, but not 100% lit
• 3rd Week
• Full Moon – Half way through the cycle the whole near
side of moon is lit
• Moon Starts to Wane (starts looking
• Waning Gibbous – near side is less than
100% lit but more than 50% lit
• 4th Week
• 3rd Quarter – 50% of the near side is in
sunlight and can be seen.
• Waning Crescent – A small portion of the
moon can be seen.
• Cycle then repeats with a New Moon
Moon Phase Song
(To the tune of “If You’re Happy and You Know It”)
If it’s waxing you’ll be seeing much more light.
It’ll be getting so much brighter on the right.
If it’s waxing then you’ll know.
For you will see more of a glow.
Soon a full moon will light up your darkest night.
When it’s waning there’s less light for you and me.
Don’t go whining ‘bout the darkness that you see.
Though the cycle’s going to end
It will soon begin again
For a cycle goes around and ‘round you see.
• 2 types of Eclipses: Solar and
Lunar Eclipses
• Sunlight streams past earth and the moon,
lighting one side of each. Beyond each is a long
thin cone of darkness where no sunlight reaches
- a shadow in space. If the moon, the sun, and
earth line up exactly a shadow crosses the Earth
or moon. An eclipse occurs when a shadow
makes the sun or moon appear to grow dark,
remember if it is dark we cannot see it.
• Lunar Eclipse – the moon becomes dark during
a lunar eclipse because it passes through
Earth’s shadow. There are two parts of Earth’s
shadow – the umbra- which is the darkest part
of the shadow, and the penumbra which is a
lighter cone of shadow. Just before lunar
eclipse sunlight streaming past earth produces
a full moon then the moon moves into the
umbra. Earth’s dark shadow seems to creep
across the moon. The moon is small enough to
fit completely in earth shadow, and so cannot
be seen.
• Total lunar eclipse – moon
passes completely into the
earth’s shadow and no part of
the moon can be seen.
• Partial lunar eclipse – if the
moon misses part or all of the
umbra, only part of the moon
is in shadow cannot be seen.
Solar Eclipses
In a solar eclipse the sun appears to
darken (and we can’t see it) because
the moon’s shadow falls onto part of
the earth.
A solar eclipse occurs when the
moon passes directly between the
earth and the sun.
Only locations in the path of the
moon’s shadow experience a solar
eclipse. Solar eclipses are rarer than
lunar eclipses.
Bright light from the sun disk
can damage your eyes if you look
directly at it.
Annular Eclipse
Earth’s Tilt And Seasons
The seasons are the result of the
Earth’s tilt on it axis. The earth’s axis is
tilted at 23.45 degrees. This tilting is
what gives us four seasons of the year
– spring, summer, autumn and winter.
Since the axis is tilted, different parts of
the globe are pointed toward the sun at
different times of the year.
• Summer is warmer than winter because the
sun’s rays strike the Earth at an angle with
is more direct during the summer than in
winter. In addition to the angle of the sun’s
rays, it is warmer in summer because the
days are longer than the nights during the
summer, allowing a longer time for the
warming to occur.
• Quick Vocab: Solstices (sol = sun; stice from stit
= stopped)
When the sun reaches the highest or lowest
point in the sky at noon a solstice occurs and
marks the longest day (in daylight hours) in the
summer, and the shortest day (in daylight hours)
in the winter. The winter solstice occurs on 12/21
or 12/22, the summer solstice occurs on 6/21 or
• Quick Vocab: Equinox: (equi = night; nox = night)
• Equinox – The day and night are equal in length.
Vernal equinox – happens in March 20th and is the
beginning of spring. Autumnal equinox – happens
in September 22 and is the beginning of fall.
NH = Spring Equinox
SH = Autumn Equinox
Rotation and
PAGE 45 - 48
• Rotation means to spin on an axis. All celestial bodies
rotate. Once started spinning objects in space tend to
keep spinning. If an object decreases in size it will spin
faster. The fact that most objects from galaxies to
planets spin in nearly the same way is a clue that they
have a common origin.
The earth’s rotation takes 23 hours and 56 minutes.
The earth and moon rotate about their axes at the
same rate so the same side of the moon always faces
the earth.
Rotation is responsible for the length of the day and
night. Rotation is responsible for the apparent
movement of the moon, stars, and planet.
• 58 days 16
hours --rotation
• Rotation =
243 days
• Rotation 23
hours 56
• Rotation 24
hours 37
• Rotation 9
hours 50 min
• Rotation 10
hours 14
• Rotation 20
• Rotation 21
• The earth moves in an almost circular but
slightly elliptical motion around the sun – this is
called revolution.
• One revolution around the sun is equal to
365.25 days – or one year.
• The moon revolves around the earth in 27.322
• Orbit is a regular repeating path that one object
in space takes around another object in space.
225 Earth days
1.9 Earth years
365.25 days
88 Earth days
12 Earth years
29 Earth years
84 Earth years
164 Earth Years