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Galaxies
• The basic structural unit of matter in the
universe is the galaxy
• A galaxy is a collection of billions of
_____________
stars , gas, and dust held together by
gravity
____________________
• An average galaxy will have over
___________________________
billion stars
100
Galaxies
• Galaxies are classified by their shape
• The three most common shapes are:
– ________________________
Elliptical (football shaped)
– ________________________
Irregular
– ________________________
Spiral
**based on the speed at which they rotate
Milky Way Galaxy
spiral
• Our solar system is part of a ________________
galaxy called the Milky Way Galaxy
• The Milky Way galaxy has about _________
billion stars
fast
• It is rotating very ___________
200
Milky Way Galaxy
2 main
spiral
“arms”
Stars
•https://www.youtube.co
m/watch?v=5az0W4Y1n
uU
Stars
• The majority of the visible matter in the
universe is made up of gas clouds, dust, and
stars
____________
• Definition:
gas held together by
– A star is a large ball of __________
gravity
– Stars produce tremendous amount of
________________
energy and shine
Stars
• The majority of the visible matter in the
universe is made up of gas clouds, dust, and
stars
____________
• Definition:
gas held together by
– A star is a large ball of __________
gravity
– Stars produce tremendous amount of
________________
energy and shine
Sun
• The star associated with the Earth and the
Sun
rest of our Solar System is called the ________
• The Sun is the main gravitational ____________
force
holding the Solar System together
• Most stars have a solar system revolving
around it
Energy in Stars
• Stars produce a tremendous amount of
energy!
• Stars create energy as a result of nuclear
cores
fusion in their ___________
Nuclear Fusion
• Nuclear Fusion is the process of combining
smaller atoms to
the nuclei of two ____________________________
create an atom with one larger nuclei
Nuclear Fusion
• What is a nucleus?
– Dense region at the center of an atom that
neutrons
consists of protons
_______________ and __________________
• Let’s look at an atom vof Hydrogen!
Nuclear Fusion
• Below is an atom of Hydrogen:
How many protons
are in the nucleus?
1!
Nuclear Fusion
• During Nuclear Fusion, two Hydrogen atoms
will be combined to form an atom with 2
protons in its nucleus
+
=
Nuclear Fusion
• During the combination of nuclei, some of
mass left over is converted into
the ____________
energy
_________________
• Our Sun converts hydrogen nuclei into
helium nuclei similar to the example
Nuclear Fusion
• Nuclear Fusion can only occur in extremely
temperature and high
high ________________________
pressure conditions
____________________
• http://www.bing.com/videos/search?q=nucl
ear+fusion+in+stars+youtube&qpvt=nuclear+
fusion+in+stars+youtube&FORM=VDRE#view
=detail&mid=97FD5A55FA8317BCF55597FD5
A55FA8317BCF555
Star Classification
• Stars are classified by two main conditions:
1. Surface Temperature
2. Luminosity
Surface Temperature
• The differences of surface temperature of
color
stars is reflected by their ______________
Think about a candle flame, the hottest
part is the closest to the wick – which is
blue!
The same pattern can be seen with
stars. The hotter the star, the bluer it
appears. Less hot stars are more
yellow/orange.
Luminosity
• Luminosity is the ___________________
brightness of a star
• However, when we observe distant stars
from Earth, we are seeing its apparent
brightness, not its luminosity
• The farther the star is away from us, the
less bright it will appear
__________
Characteristics of
Stars
• Reference Table – Page 15!
• Characteristics of Stars
1. Look at the X axis, what is the variable?
What is it measured in?
2. Look at the Y axis, what is the variable?
3. As you increase along the X axis, what
happens to temperature?
Characteristics of
Stars
4. Which star is more luminous – Alpha
Centauri or Rigel?
5. Which star has a higher surface
temperature – Spica or Polaris?
6. Read what’s in the parenthesis under
Luminosity – explain why this is so.
7. Find Polaris on the table. Does it have a
high luminosity? Is this what you would
have expected?
Characteristics of
Stars
8. What is the approximate color of Procyon
B?
9. Is there any relationship between
luminosity and color of the star?
Star Types
• There are 5 main types of stars:
– Main Sequence Stars
– Giant Stars
– Super Giants
– White Dwarfs
– Black Dwarfs
Main Sequence
• About 90% of all stars are Main Sequence
stars
• Main Sequence stars are generally average
_____________
size
• For all Main Sequence stars, as surface
temperature starts to increase, luminosity
increases
also _________________
• Most stars spend the majority of their life as
Main Sequence stars
Main Sequence
• The increase in luminosity that Main
Sequence stars go through is a result of its
temperature
increasing ________________________
• Our Sun is a Main Sequence star of
yellow
____________ color
Giant Stars
• Giant Stars are often referred to as “The Red
Giants” because of their
_________________________________
red and orange coloring
• These stars are extremely large! (about 10x
the diameter of the Sun)
• They have an extremely high
luminosity
__________________ but a low temperature
Super Giants
• Super Giant Stars can be anywhere from 100
to __________ times the diameter of the Sun!
• These stars are extremely luminous
• Super Giants usually explode in a
tremendous event called a
supernova
_______________________
• In order for a star to eventually become a
Super Giant, it must have started out much
larger than the Sun
1000
White Dwarfs
• White Dwarfs are _____________!
small
• They are usually about the size of the Earth
• White Dwarfs can be anywhere from white
to _________
blue in color
low in luminosity
• They are very hot but ________
• Represent the last luminous stage of a star
Black Dwarfs
• When a White Dwarf cools and no longer
energy it is considered a
emits any ______________-,
“dead” star – or a Black Dwarf
• These stars have stopped nuclear fusion and
no longer produce any nuclear energy
dense
• They are extremely ____________
Life of a Star
• https://www.youtube.com/watch
?v=PM9CQDlQI0A
Life Cycle of Stars
• Stars, like many objects on Earth, have a
evolution of features,
beginning, an _________________
and an ending
• Just like us, stars are“born”
___________
Star Birth
dust and
• Stars originate from clouds of __________
gas molecules
• These star forming clouds are called
nebulas
__________________
Nebulas
• Nebulas were created from the masses of
_________________
matter that were released during the
Big Bang
• Eventually, some of the gas and dust particles
clump together
in a nebula will begin to _____________
• As these clumps gain more mass, they build
gravitational pull that
up a stronger __________________________
causes more and more matter to be sucked
into it
Nebulas
• Once this mass gains enough size (reaches
about the size of Jupiter), the gravitational
pull results in high enough temperature
_____________________
and ___________________
pressure to start nuclear fusion!
shine as it
• The ball then begins to _____________
radiates energy --- thus, a star is born!
Nebulas
Main Sequence
• Every star begins its journey on the Main
Sequence after it is created in a nebula
• All stars spend most of their lives as a Main
Sequence star
• These stars will range greatly in their
mass
__________,which
will affect the rest of their
lives
Smaller Stars
• Stars with a mass similar to our Sun and
smaller will spend billions of years as a Main
Sequence star and eventually will become a
_____________________
Red Giant
hotter and
• As these stars age, they get ______________
luminous
more ___________________
Smaller Stars
• After billions of years, these stars eventually
use up most of their nuclear fuel used for
fusion and collapse to form a
____________
__________________________
White Dwarf
• They will then slowly die as they run out of
nuclear fuel completely and become a
Black Dwarf
________________________
Smaller Stars
dense
• These Black Dwarfs are extremely ____________
and have a very strong gravitational pull
light
• However, they no longer emit any __________
because nuclear fusion has stopped
Smaller Stars
Gas and
dust cloud
- Nebula
Black
Dwarf
Main Sequence Star
Red Giant
White
Dwarf
Red Super
Giant
Larger Stars
1.5
• Larger stars are any star that is ________times
the mass of our Sun
shorter
• These stars exist for much _______________
periods of time (approximately 100 million
years)
large Main
• These stars start as very ___________
Sequence stars
Larger Stars
Super Giants
• Next, they become _________________________
explode in an event
• They eventually ___________________
called a Supernova
Larger Stars
explosion
• A supernova is a stellar __________________
• When nuclear fusion no longer takes place in
collapses and
the stars core, the core _________________
releases a huge about of energy
• A Supernova will occur about once every 50
years in a galaxy the size of the Milky Way –
which means they occur about every second
in the universe!
Larger Stars
rapidly
• During a Supernova, the star _____________
collapses, forming a mass much smaller than
a White Dwarf
dense that only
• They get so small and ____________
neutrons can exist – these are called
_________________________
Neutron Stars
Larger Stars
Gas and
dust cloud
- Nebula
Main Sequence Star
Red Super
Giant
Supernova
Neutron
Star
HUGE Stars
• When the most massive stars collapse, the
density is so large that an extreme
______________
gravity field is created
light or any form of energy can
• No ____________
escape
Black Hole
• This is called a _____________________