Study Guide
Module 2
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Big Bang : Scientific theory of how the universe started.
 All matter in the universe was once a single point.
 Gravity and energy may have caused the matter to expand
 The universe is still expanding
 After the Big Bang, the universe contained pockets of dust.
Law of Universal Gravitation: that all objects attract each other.
 All objects that have mass attract each other.
 Objects with large masses (like planets and some stars) have a
large amount of attraction
 Small objects like people, houses, and cars have a very small
amount of attraction
Explosion of
great force
Dust and clouds
appear
Clouds and dust pull
towards each other
in a spiral
Tightly packed
dust cloud form
planet or star
Stars start out
in a giant
nursery called
a Nebulae
Then gravity pulls all
the dust and gas
together until the pull
is soo strong it forms
a ball, this can take
millions of years!
Then as the pressure and
mass increase, the heat
increases too! Soon it gets so
hot it goes through nuclear
fusion, where the atoms in
the dust and gas form helium
and poww!~ a star is born!
Stars + Stars + Stars +
planets = the Universe!
It’s Huge!!
Our Galaxy is called the
Milky Way. It is a spiral
galaxy and contains
billions of stars!
Eventually the gravitational
pull of our Sun (a main
sequence star) pulled all the
newly formed planets, comets,
etc into orbit around it. And so
our galaxy was born!
The Milky Way is said to have around 100,000,000,000 stars!
And there are 100,000,000,000 other galaxies in the Universe.
That leaves the universe with trillions and trillions of stars! Many scientists
estimate that the universe has 400,000,000,000,000,000,000,000 stars.
A galaxy is a group of stars, planets, gas, and dust that is
held together by gravity.
There are three different types of galaxies:
Type
Shape
Gas/Dust content
Age
Irregular
No real shape
Contain lots of gas Young
and dust
Spiral
Revolve around
single point
Some gas and
dust
Middle
Elliptical
Circular and
concentrated
Little to no gas
and dust
Older
Speed of Light: light travels 800,000 times faster than sound. In
fact, light is the fastest thing in the universe that we know of!
Light travels:
 Around the Earth in 0.13 sec
 To the Moon in 1.3 sec.
 To the Sun in 8 min.
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The nearest Star to Earth is Proxima Centauri. It takes light 4.2
years to travel from the star to our eyes! This means that 4 years
ago the star could have exploded and we would have no idea!
A light year is the distance that light can travel in one year. So if an
object is one light year away, it will take light one year to get there.
 1 light year = 9,461,000,000,000 km or 5,879,000,000,000
miles
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Light years are used to measure distances in space because
their large size allows us to talk about vast distances using
smaller numbers.
For example, it is 20,000,000,000 light years to the edge of the
universe which equals 117,580,000,000,000,000,000,000 miles!
Scientists use four different characteristics to help them classify and describe stars.
Temperature
Size
Composition
Brightness
Temperature - Determines the color of the star
Cold = red, warm = yellow, Hot = white, Super hot = blue
Star composition - Provides a "fingerprint" for stars. Most common elements are
hydrogen and helium
Star Brightness - Is determined by star size, distance away, and strength of light
Apparent Magnitude- The brightness of a star as it appears from the earth, without
the effect of the earth’s atmosphere
Absolute Magnitude- the actual amount of light that a star gives off. (brightness)
Star Size – Neutron, medium, giant and supergiant, Dwarf
The HR diagram is a scatter graph used by scientists to study the stars. The graph shows
the relationship between the stars' absolute magnitudes versus their temperatures (C˚).
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Y – axis = Star’s Absolute Magnitude
X – axis = Star’s temperature
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When we compare the absolute
magnitude and temperature of stars,
we will see that the brighter a star is,
the hotter it will be.
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The main reason that the HR Diagram
is so useful is you can tell the size of
the star by plotting it on the graph.
The different sizes of stars form a
pattern.
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Types of Stars!
Type
Size
Surface
temperature
Brightness Weight
Details
Neutron
Small
Very High
Dull
Heavy :
1tbs = 10 tons!
Tight and compact
Dwarf
Same as Earth
High
Little to no
light
Less than the
sun
Half the weight of a
neutron
Medium-Size
(main
sequence)
Same as the
Sun!
Average
Average
Moderate/Aver
age
Most stars are in
this category
Giant
10-100 times
larger than sun
Low
Bright
Very big
Becomes a dwarf
when it dies
Supergiant
1000 times
larger than sun
Low
Very Bright
Largest in
universe
Becomes a black
hole when it dies
Stars are formed, mature, and eventually cease to function as stars!
There are two tracks a star can take in its life…
Or…
A black hole is formed when a supergiant star dies and are hard
for scientists to study because they are black and hard to see.
Mass causes gravity. The more mass an object has, the more gravity it applies.
Now, imagine an astronomical object so massive that its gravity becomes large
enough to crush itself into a small volume. The gravity of this object would be so
large that even light, the fastest moving phenomenon in the universe would not
be fast enough to break free of the pull.
Since light cannot escape from it, it would not be possible to see the object. The
object would pull in all the light around it and so appear black. Stars have very
high mass and therefore very high gravitational pull. The atoms of a star
undergo nuclear reactions and release huge amounts of energy. The gravity of a
star pulls the matter forming the star towards its center while the energy from
nuclear reactions pushes the matter out. These two forces are in balance.
Eventually, the matter undergoing nuclear reactions runs out. If this core
contains enough mass, the structure of the atoms forming the core breaks under
the high gravity and the core collapses into a black hole. Thus, black holes form
when very high concentrations of mass are squeezed in a small volume.
• High mass stars will not live as long as low mass stars.
• The high mass stars will be hotter and brighter. Because of this they will burn
through their fuel faster and die sooner.
• Small mass stars will live for 100 billion years.
• Average mass stars will live for 10 billion years.
• Large mass stars will live for 5 billion years or less.
1) Solar prominences are flame-like arcs into
space, which are associated with sunspots
and magnetic fields. Some solar
prominences last for many days, others for
only minutes.
5) The chromosphere is the middle layer
atmosphere of the sun. Temperatures in the
chromospheres average more than 25,000
ºC.
The photosphere is considered the surface
of the sun. Temperatures in the photosphere
are usually around 6,000 ºC.
2) Solar Flares- Flares, of all solar events, are the shortest…lasting only minutes..(pause)..
and the most violent… creating a fusion explosion equal to millions of hydrogen bombs.
The explosion of a solar flare is so violent that, like an earth quake, pressure waves race
across the entire immense surface of the sun in just a few hours.
4) Corona-The corona is the outermost part of the suns
atmosphere. The temperature of the corona exceeds
one million ºC and can only be seen during an eclipse,
where the moon covers up the sun leaving only the
corona exposed, or through a special solar telescope.
3) Sunspots- Dark regions on the sun’s
surface where the temperature within the
spot is lower than the rest of the sun. These
cooler spots come and go and can be effect
earth. When there are a large number of
sunspots, the magnetic activity that comes
from these sunspots can disrupt
communication systems on earth. Cell
phones, radios, and TV antennas will not
work as well.
The electromagnetic spectrum is the range for light shown in the graph below.
We can only “see” a very small range of actual light due to the frequency of the light
waves. Sound waves are different from light waves and are not found on the graph.
Sound waves require matter to travel through, where light does not.
The range of colors we “see” are the frequencies visible to our eyes.
If you combine all frequencies they will appear as white light,
which is just the same as black being the absence of light.
DID you know!?
Ultra-Violet frequencies
are visible to insects
and snakes can sense
infra-red waves!
The non-absorbed frequency
that is reflected by the object
is what we see and how we
get different colors.
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Light does not travel in a perfectly straight line but moves
like a wave in the ocean. There are two important
properties of waves that determine the type of light.
Wavelength: distance between two crests.
Frequency: Number of times a wave crest
passes by a point in one second.
Wavelength and Frequency are Related
 if you change the wavelength of a wave it will affect the
frequency,
 if you change the frequency of a wave it will affect the
wavelength.
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Types of light can be determined by studying the wavelength
and frequency of the light.
Light has a “fingerprint” called an emission spectrum. When
an atom lets off or emits light it does not let off just one color.
It emits a combination of a few colors. The emission spectrum
is all the colors that the atom emits. Here is the emission
spectrum for iron.
Spectrometer are the instruments that
scientists use to see the atoms emission
spectrum. They take the light and bend it
through a prism to break them down into their
colors.
Stars and planets are made up of many different
atoms. When scientists pass the light coming
from the star or planet through the spectrometer
they get an emission spectrum. They then analyze
the emission spectrum to see which atom's
individual light fingerprints are in there. In this
way, they can use the light from stars and planets
to find out what the star or planet is made of.
Types of light emission fingerprints:
White Light
 White light is light that contains every color of the rainbow. Notice that every
color is in white light’s emission spectrum.
Hydrogen
 Hydrogen’s spectrum has some different shades of violet, some shades of
blue and a red. Hydrogen is the most abundant element in the universe.
Sodium
 Sodium’s spectrum contains two shades of yellow.
Helium
 Helium is another very abundant element in the universe. Helium’s
spectrum contains some different shades of blues, a yellow and a red.
Neon
 Neon is the atom that is contained in a neon light. Can you see why a neon
light looks orange?
Mercury
 Mercury’s spectrum contains purple, blue, green and two shades of yellow.
Be sure to review:
 The Big Bang Theory.
 The parts of the universe.
 The distances in the universe.
 The properties of stars.
 HR diagrams.
 The stages of a star's life.
 The physical appearance of the sun.
 The characteristics of the electromagnetic spectrum.
 How the electromagnetic spectrum is used to study stars
and planets.
Module Vocabulary
Absolute Magnitude
Apparent Magnitude
Betelgeuse
Chromosphere
Big Bang
Fusion Ignition
Super Giants
Neutron
Spiral Galaxy
Milky Way
Corona
Emission Spectrum
Frequency
Galaxy
Law of Universal
Gravitation
Nebula
Main Sequence
Dwarf
Irregular Galaxy
Light Year
Photosphere
Wavelength
Proxima Centauri
Solar Flare
Solar Prominence
Spectrometer
Protostar
Giant
Black hole
Elliptical Galaxy
Speed of light
Sunspot
Frequency