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Unit Test Study Guide:
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Astronomy
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Use the summary points below as a resource to help you study for our unit test next class!
BIG BANG THEORY:
 Astronomers’ explanation for the start of the universe is called the big bang
theory.
 According to the big bang theory, the universe was at first very hot and small.
It was no larger than a period at the end of a sentence. The universe then
exploded. That explosion is called the big bang. The bang happened billions
of years ago. Scientists believe since the big bang explosion that our universe
began to condense and form galaxies, then solar systems. Since the explosion,
the universe continues to expand today.
*From largest to smallest, the composition of our universe is:
UNIVERSE, GALAXIES, SOLAR SYSTEMS
GALAXIES:
Spiral Galaxies:
 Have a bulge in the center and arms that spiral
outward
 Contain bright, young stars
 Our galaxy, the Milky Way Galaxy is a spiral galaxy
 Our solar system is located at the base of one of
the galaxy arms
Heliocentric Model
 There are two models that developed over
time to describe the function of our
universe:
o Geocentric Model – earth is
perceived to be at the center of the
revolving planets and the sun
o Heliocentric Model – Earth and the
other planets revolve around the sun
o The invention of the telescope years
later confirmed that the heliocentric
model was indeed the true model
Geocentric Model
GEOCENTRIC & HELIOCENTRIC MODELS:
Elliptical Galaxies:
 Look like flattened circles, ovals or ellipses
 Contain old stars
Irregular Galaxies:
 Have no definite shape
 Contain bright, young stars
 If it does not shape like a spiral or elliptical galaxy, it
is classified as an irregular galaxy
INNER PLANETS:
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The four inner planets are called terrestrial planets. This means they have rocky
or solid surfaces.
The four inner planets are (in order from the sun): Mercury, Venus, Earth, Mars
Earth has liquid water on its surface.
Venus is Earth’s twin because it is about the same size and it’s structure is similar
to Earth’s
Scientists think that a large amount of liquid flowed on Mar’s surface in the
distant past. This is because there are ancient coastlines on the surface.
Venus’ is the hottest planet. This is because Venus’ atmosphere traps heat from
the sun and does not let it out. This trapping of heat is called the greenhouse
effect.
Mars is considered the red planet because it’s surface is covered in red dirt.
Mercury is too close to the Sun to have an atmosphere.
Currently, Earth is the only planet that can support life. Mars may have supported
life in the past, and could possibly support it in the future.
COMETS, ASTEROIDS AND METEORS:
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Comets are loose collections of ice, dust and small rocky particles.
Most asteroids revolve around the sun between the orbits of Mars and
Jupiter. This area is called the asteroid belt.
Meteoroids come from comets or asteroids.
Meteoroids are chunks of rocks in outer space. (has the most O’s for outer
space)
Meteors are meteoroids that make it into Earth’s atmosphere and move
quickly across our night sky. We often call meteors “shooting stars”.
Meteorites are meteoroids that hit Earth’s surface. (has the most E’s for
Earth’s surface)
A comet has three parts: the coma, nucleus and two tails.
A comet’s two tails always face away from the sun as it orbits the sun.
Identify:
Comet
Asteroids
Meteorod (top), Meteorite (bottom)
Meteor (pic on the side)
OUTER PLANETS:
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In order from the sun: Jupiter, Saturn, Uranus and Neptune are much larger and
massive than Earth.
These planets are made of gas and liquid which makes them jovian.
Most of the outer or jovian planets are made of hydrogen and helium, like our
sun.
Jupiter is the largest planet in the solar system. It has a red eye that can be seen
from Earth. Scientist believe this “eye” is a hurricane with high winds.
Saturn is the second largest planet.
Uranus’ axis rotation is at a 90 degree angle, which means it is on its side. It’s
rings are vertical instead of horizontal.
Neptune’s atmosphere has clouds and it is about the same size as Uranus.
Scientist believe Neptune is shrinking.
Pluto is no longer considered a planet and has been given a new classification –
dwarf planet.
None of the outer planets have the ability to support life.
Neptune
Uranus
Saturn
Jupiter
RELATIVE SIZE & RELATIVE DISTANCE:
Relative size means how big is an object in relationship to others as one is a determined
to be a certain size. So if Earth is this big, then that means Jupiter is this big. Take a look
at the relative sizes of the planets below:
Relative distance means how far an object is from another as one object is
determined to be from a certain distance from the other. Take a look at relative
distance in the picture below (recall our cash register tape activity).
GRAVITY & INERTIA:
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Gravity is the force that attracts all objects toward each other
Gravitational force is stronger when two objects are closer together.
Gravity is the force that pulls objects toward each other. Any two objects attract
each other with the same amount of gravitational force.
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Gravity is influenced by mass of the objects and the distance the objects are from
one another. This means the larger the mass, the gravitational force between
two objects has less impact.
Inertia: the tendency of an object to not change its motion
Inertia is why the planets stay in motion and never stop. (if it’s moving it wants
to continue moving. If it is not moving, it doesn’t want to move.
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So, the more mass an object has, the stronger the
impact of its gravitational force. In the picture to
the left, Earth has more mass, so it has more
impact on the person and the moon.
The closer objects are to one another the stronger
their gravitational force. Therefore, if the moon
were this far away from Earth, Earth’s
gravitational force would be weaker. This means if
this were true, our moon might not orbit earth since
the force would be weakened.
This diagram shows what would happen if there was no gravity
to balance out the inertia of the moon. In the absence of gravity,
our moon would not orbit Earth, it would just head in one
direction, in a straight line, forever.
ROTATION VS. REVOLUTION:
 Earth moves through space in two major ways:
o rotation – the spinning of Earth on its axis
o revolution – the movement of one object around another. In this case the planets
move around the sun in an orbit
 We experience night and day because of the Earth’s rotation.
 We experience seasons because of Earth’s tilt on its axis and revolution around the
sun.
SEASONS:
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The tilt of Earth on its axis causes seasons.
Autumn and fall are the same season. Scientists refer to fall as autumn.
To identify which season a particular hemisphere is experiencing, first look to see
which hemisphere is tilted towards the Sun. This hemisphere is experiencing
summer.
The hemisphere tilted away from the Sun is experiencing winter.
If Earth is “to the side” of the sun, meaning it is neither tilted towards or away from
the sun, autumn or spring is being experienced.
To determine whether autumn or spring is being experienced, check to see which
season the hemisphere was experiencing prior to Earth getting into its current
position.
Look at the picture above, on the left, the top part of the Earth’s
axis is pointing TOWARDS the sun, so the northern hemisphere is
in summer. Since the bottom of the axis is pointing away from the
sun, this means the southern hemisphere is in winter. Look at the
other side of the sun. The axis is in the opposite position, so the
seasons have changed.
SOLSTICES & EQUINOXES:
 Solstice - The two days of the year where the sun reaches farthest north or south of the equator.
o Summer solstice begins the longest of daytime. Winter solstice begins the longest of night
time.
o The north pole and south pole receive ONLY day or night depending on which season they
are experiencing.
 Equinox - The two days of the year where neither hemisphere is titled toward or away from the sun
resulting in a day or equal sunlight and night
o The day of autumn equinox (first day of autumn) and the day of vernal (spring) equinox
results in 12 equal hours of day and 12 equal hours of night time everywhere on Earth.
MOON PHASES:
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The changing relative positions of the moon, Earth and sun cause the phases of the
moon.
The phase of the moon you see depends on how much of the sunlit side of the moon
faces Earth.
There are eight phases of the moon which are new moon, waxing moon, first
quarter, waxing gibbous, full moon, waning gibbous, third quarter, and waning
crescent
From new moon to full moon, light increases. From full moon back to new moon light
decreases.
During the waxing phases, the light is on the right. During the waning phases, the
light is on the left.
To determine where the moon phase starts (no matter where the sun is), find the
moon that is directly in front of the sun – this is the new moon. The phases continue
by moving up and away from the sun.
What’s the Phase?
Waxing Crescent – A little part of the
moon’s right side is in sunlight.
Full Moon - The moon's entire disk is in
sunlight because the Earth is between
the sun and the moon.
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New Moon - The moon's disk facing us is
dark because the moon is between the sun
and the Earth.
Last Quarter - The left half of the moon's
disk is in sunlight.
ECLIPSES:
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A solar eclipse occurs when the moon passes directly between Earth and the sun.
The umbra must touch the Earth’s surface for this to happen.
Solar eclipses happen during the day and we see a new moon (black) directly
covering the sun, with the sun’s light shining bright around the new moon’s edges.
During a lunar eclipse, Earth’s blocks most of the sun’s light from reaching the
moon. It bends the suns light in a way that only allows red light to be reflected on
the moon through Earth’s shadow.
Lunar eclipses happen at night time and we see the moon as red.
Eclipses can be partial or total.
An umbra is the darkest part of an object’s shadow.
A penumbra is the lighter part of an object’s shadow cast at an angle.
Total vs. Partial Solar Eclipse
Partial vs. Total Lunar Eclipse
penumbra
lunar eclipse
LIFE CYCLE OF A STAR:
Life Cycle of Low and Medium Mass Stars:
main sequence – the star begins to
White dwarf – as the star
nebula – a large cloud of
protostar – the first star; gravity pulls a
gas and dust
nebular together into a protostar
heat up and becomes hot.
Based on its temperature,
the star enters the main
sequence as a low, medium
or high mass star.
comes out of fuel, it
becomes a white star.
Once the fuel runs out,
it becomes a black
dwarf.
nebula – a large cloud of
protostar – the first star; gravity pulls a
main sequence – the star begins to
supernova – as high mass
gas and dust
nebular together into a protostar
Life Cycle of High Mass Stars:
heat up and becomes hot.
Based on its temperature,
the star enters the main
sequence as a low, medium
or high mass star.
stars begin to run out of
school an explosion,
called a supernova
occurs
OR
black hole – high mass stars
with the greatest mass
become black holes
after the supernova
neutron star – some high mass
stars form neutron stars
which is the leftover mass
from the supernova
CONSTELLATIONS:
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Ancient cultures imagined that constellations formed animals or peoples.
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Constellations are a group of stars (imaginary patterns) that are visible in a certain region of the sky.
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Constellations appear in the same section or region of the sky.
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Since generally, the location of stars does not change, early astronomers used stars to map the night’s
sky. Since certain constellations can be found in the sky during certain seasons, ancient cultures also
used constellations to know when to harvest the land and to track time (when a season was coming).
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The constellations that can be seen in the northern hemisphere may not be visible to people who live
in the southern hemisphere.
 The regions of the sky in this picture show that
constellations appear in specific locations whenever
we can see them. If you observe this picture, you
should notice that they resemble states. Just like we
can travel to certain states by knowing their
location, ancient cultures used the knowledge of
knowing which constellations appeared in which
section of the sky to know which way was east,
north, south or west. For instance, if I know that the
little dipper has the north star in it’s handle, all I
have to do is find the little dipper, locate the north
star and heads towards it to travel north.
SPACE TECHNOLOGY:
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NASA has used space shuttles to perform many important tasks. These include taking
satellites into orbit, repairing damaged satellites, and carrying astronauts and
equipment to and from space stations. a space station provides a place where longterm observations and experiments can be carried out in space.
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A space shuttle is a spacecraft that can carry people into space. A space shuttle can
then return to Earth and land like an airplane. A space shuttle can be used many times.
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A space station is a large satellite where people can live and work. The international
space station is in orbit around Earth.
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A space probe is a spacecraft that carries specific scientific instruments into space. The
instruments collect information. No humans are ever on board a space probe.
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Some space probes land on other planets. Some space probes fly around other
planets.
o Some space probes are small robots called rovers. Rovers are more robotic and
move around on the surface of a planet and collect information.
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Space probes have been sent to all planets.
space shuttle
docked
space shuttle
space probe
space rover
International
Space station
STUDY PRACTICE:
VOCABULARY SECTION: Update your vocabulary dictionary with the words below. Be sure to include the
definition and a visual drawing of each. I have included definitions of each word in
their appropriate sections in this study guide.
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greenhouse effect
terrestrial planet
Big Bang Theory
geocentric model
heliocentric model
rotation
revolution
spiral galaxy
elliptical galaxy
irregular galaxy
1. Pluto is a(n):
a. inner planet
c. dwarf planet
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jovian planet
gravity
inertia
umbra
penumbra
solstice
equinox
space probe
space rover
asteroid belt
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meteor
meteorite
meteoroid
comet
waxing moon
waning moon
space shuttle
b. outer planet
d. gas giant
2. The region between Mars and Jupiter where many rocky objects are found is the
a. comet zone
b. meteoroid haven
c. asteroid belt
d. Kuiper belt
3. A meteoroid that reaches Earth’s surface is called a(n):
a. comet
b. meteorite
c. asteroid
d. meteor
4. Pluto is a(n):
a. inner planet
c. dwarf planet
b. outer planet
d. gas giant
5. Why does Mercury have very little atmosphere?
6. What evidence do astronomers have that water once flowed on Mars?
7. Compare and contrast meteoroids, comets and asteroids.
8. Observe the picture below. Based on what you know about comets, draw the sun in the position
that would show a comet as it orbits the sun.
Matching:
9. Match the term with its description:
Term:
1. spiral galaxy
Descrip on:
a. galaxy that does not have any
certain shape and bright young stars
2. ellip cal galaxy
b. galaxy with a bulge in the middle,
arms that curve and has many
bright new stars
3. irregular galaxy
c. galaxy that looks like a round or
fla ened ball and contains only old
stars
10. Describe the similarities and differences between the inner and outer planets.
11. Use what you know about moon phases to shade and label the moon phases below.
12. Complete this chart to see comparisons and contrasts of Solar and Lunar Eclipses.
Moon Phase
Visible to those in the…
Total solar
Partial solar
Total lunar
Partial lunar
13. Explain how you know which season the Northern and Southern Hemispheres are experiencing in
the picture below.
14. What is the big bang theory?
15. Sketch a picture of the geocentric and heliocentric models below. After you make your sketch,
write one sentence that describes each of them below each picture.
heliocentric model:
geocentric model:
16. How does the model below describe the universe, galaxies and solar systems?
solar systems
galaxies
universe
17. Place the letter of your choice beside the picture that best defines or represents the type of galaxy:
18. What is the difference between rotation and revolution? Please also identify what happens as a
result of rotation and revolution (hint: night or day).
19. The earth is in between the moon and the sun. The moon appears red. What is happening,
explain.
20. Sketch a picture of the sun, earth, moon, penumbra, and umbra during a solar eclipse.
21. What is the difference between a high mass star’s life cycle and a low/medium mass star’s life
cycle?
22. What are constellations?
a.regions of the sky that contain recognizable star patterns
c.star patterns
b. stars
d. galaxies
23. Jazzmine is lost in the woods. She knows that her cabin is east of where she is currently located.
How might she use the night sky to figure out how to get back to her cabin?
24. How has space technology been used to advance what we know about outer space?