Download The Universe - Solon City Schools

The Universe
Chapter 20
1
The Life and Death of Stars
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Stars are huge spheres of hot
gases that emit light and other
forms of electromagnetic
radiation.
The distance between stars is
measured in light years (the
distance that light travels in
one year).
Star produce energy by
nuclear fusion, fusing
hydrogen in to helium.
2
Layers of a Star
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Core(15,000,000 K-site of
nuclear fusion)
Radiative Zone (2,500,000 K)
Convective Zone (1,000,000
K)
Photosphere(6000 K-layer that
produces light)
Chromosphere(4000-50,000Klayer that produces color)
Corona(2,000,000 K-layer that
produces ultraviolet rays)
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Studying Stars

Stars are classified by
brightness.
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Color of a star indicates the
temperature of a star.
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Absolute magnitude is the
brightness of a star at a
distance of 10 parsecs.
Apparent magnitude is the
brightness of a star as seen
from the earth.
Hotter stars are blue in color.
Cooler stars are red in color.
The spectral lines can indicate
the composition of a star.
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Fate of Stars

The Hertzsprung-Russell
diagram is a graph of all the
stars in the Milky Way Galaxy.
 The temperature is on the
x-axis.
 The luminosity or
brightness is on the y-axis.
 Our sun is a main
sequence star (typical).
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Birth of a Star
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Stars are born from a
cloud of gas or dust
called a nebula.
The cloud condenses to
form a protostar.
The protostar becomes a
star when the core of the
star reaches 15,000,000
K and nuclear fusion
begins.
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Star Life
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The more massive stars
live for millions of years.
The less massive stars
live for billions of years.
Through out the life of
stars, elements are fused
into larger elements
(hydrogen to helium to
carbon to oxygen to iron).
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Life Cycle of Stars

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Stars that are less
massive go from a
main sequence star to
a red giant and
finishes as a dwarf
star.
Stars that are more
massive go from a
giant star to a
supernova.
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End of a Star’s Life
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Star that are less than 1.4
solar masses will use up
all of its hydrogen and
helium and become a
white dwarf.
Stars that are between
1.4-3.0 solar masses will
produce a Type I
supernova, leaving a
neutron star.
Stars that are greater
than 3.0 solar masses
produce a Type II
supernova, collapsing
and producing a black
hole.
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Galaxies
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A galaxy is a collection of
millions or billions of stars.
Galaxies are grouped in
clusters.
The Milky Way is a spiral
galaxy (our galaxy).
Types of Galaxies (by shape):
 Spiral galaxies (blue stars).
 Elliptical galaxies (red
stars).
 Irregular galaxies.
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Quasars

Quasars are the most
distant and most
radiant objects in the
universe (center of
distant galaxies).
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Origin of the Universe
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The universe is
everything in space.
The Big Bang Theory
states that the universe
began with a gigantic
explosion 10 to 20 billion
years ago.
Proof of the theory is the
red shift of stars showing
the universe is
expanding.
12
Future of the Universe
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The universe will keep
expanding forever
(Hubble).
The expansion of the
universe will gradually
slow down, and the
universe will approach a
limit in size.
The universe will stop
expanding and start to fall
back in on itself.
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Tools to Study the Universe
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Reflecting telescopes
use mirrors to magnify
the image.
Refracting telescopes use
lenses to magnify the
image.
Radio telescopes collect
radio waves to study the
stars.
Spectroscopes analyze
the light given off by stars
to indicate composition,
movement and
temperature of stars.
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Reflecting Telescope
15
Refracting Telescope
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Radio Telescope
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One of the greatest advancements in astronomy
was the telescope. Which is the correct order of
advancements?
D.
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18
Why do astronomers measure interstellar
distances in light years instead of kilometers or
miles?
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Light years are a
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Miles and kilometers are
too small of a unit.
Miles and kilometers are
too large of a unit.
I don’t have a clue . . .
help me!
Li
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Which of the following correctly shows the age
progression of an average star?
A.
B.
C.
D.
Main sequence→White
Dwarf→Red Giant
→Nebula
Red Giant →White
Dwarf →Main Sequence
→Nebula
Nebula →Main
Sequence →Red Giant
→White Dwarf
White Dwarf →Red
Giant →Main Sequence
→Nebula
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What is the next likely stage of a
protostar?
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Super Giants
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What type of galaxy is shown in the
picture?
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B.
Spiral
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C.
Elliptical
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D. I have no idea … I need help!!!
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Review Questions
Which unit is used to measure the
distance between stars?
 light year
 Which type of telescope uses mirrors to
see stars?
 reflecting telescope
 What happens to a star at the end of its
life, that is more than 3 solar masses?
 supernova to a black hole

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Review Questions
What is the color of stars that are cooler?
 red
 What is the type of brightness of a star
when it is observed from the earth?
 apparent brightness
 What is graphed on the x-axis of the H-R
diagram?
 temperature

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Review Questions
What is graphed on the y-axis of the H-R
diagram?
 brightness or magnitude
 How does a star produce energy?
 fusion
 How do we know that the universe is still
expanding?
 red shift

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Review Questions
Name the three types of galaxies.
 irregular, spiral, elliptical
 What is used to classify galaxies?
 shape
 What is the color of very hot stars?
 blue
 Name the three types of telescopes.
 reflecting, refracting, radio

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Review Questions
How do you calculate the distance that
light travels in one year?
 Multiply the number of seconds in a year
by the speed of light.
 What is the speed of light?
 300,000 km/s
 What is the name of the theory of the
creation of the universe?
 Big Bang

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Review Questions
What do we call the most distance objects
in the universe?
 quasars.
 How long ago did the Big Bang take
place?
 10 to 20 billion years ago
 What will the sun turn into when it dies?
 white dwarf
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Review Questions
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Which galaxy do we live in?
Milky Way
What type of galaxy is the Milky Way?
spiral
Which type of galaxy has old red stars?
elliptical
Which type of galaxy has young blue stars?
spiral
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Review Questions
What can the spectrograph tell us about a
star?
 compostion, temperature, and whether the
star is approaching us or going away
 Who proposed that the universe is
expanding by the red shift?
 Edwin Hubble
 What does hydrogen fuse into in a star?
 helium
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Review Questions
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When does a star change from a nebula and
protostar to a star?
The core of the star heats up to 15 million K to
begin nuclear fusion.
What happens to a medium size star (1.4 to 3.0
solar masses) when it dies?
supernova to a neutron star
What do you call the brightness of a star at the
distance of 10 parsecs?
absolute magnitude
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Review Questions
What happens to a star from birth to
death?
 nebula to proto star to either a white dwarf,
supernova to neutron star or supernova to
black hole
 How is the mass of the star related to the
length of life of a star?
 low mass, long life; high mass, short life
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