Download Notes Chapter 20 - Universe and Stars

Formation of the Solar System
Chapter 19
Section 3
Astronomy – A history
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The first record of the study of astronomy
was in Nabta, Egypt
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Group of stones were arranged to line up with
the sun on the longest day of the year
(summer solstice)
Stonehenge, England – one of the world’s
oldest observatories
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Stones are aligned with the winter and
summer solstice
The Universe
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THE SUM OF ALL SPACE,
MATTER, AND ENERGY THAT
EXISTS, THAT HAS EXISTED IN
THE PAST AND THAT WILL EXIST
IN THE FUTURE.
Inside of this universe there are
galaxies that hold millions of stars.
We are located in one of these
galaxies…THE MILKY WAY
GALAXY.
The Milky Way Galaxy
Models of the Earth
History of the Universe Model
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The first models had the Earth in the
center of the solar system – GEOCENTRIC
Greeks were the first to try to determine
Earth’s place in the universe
Aristotle used math and models to
illustrate the universe
Models of the Earth
History of the Universe Model
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Copernicus was the first to put the sun in
the center of the solar system (1543) –
HELIOCENTRIC
Also explained that the earth and other
planets orbited the sun in perfect circles.
Models of the Earth
History of the Universe Model
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Kepler (1605) – improved on the
Copernicus model
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Explained that the orbits are actually ellipses
or ovals
At this time, there was no mathematical proof
so it was not considered true.
Models of the Earth
History of the Universe Model
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Newton (1687) – Explained Gravity
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Helped to explain why the planets traveled in
elliptical orbits around the sun
Explained that every object in the universe
exerts a gravitational force on every other
object.
Gravitational Forces
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Every object in the universe has a
gravitational force.
Larger objects have more gravitational pull
compared to smaller objects.
Smaller objects that are close enough to a
larger object will ORBIT the larger object.
Formation of the Solar System
The NEBULAR MODEL
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This is the most widely accepted model for
the formation of the solar system (-p. 648649)
NEBULA – A large cloud of dust and gas in
space…region where stars are born or
explode
According to this model the sun and
planets formed from a cloud of gas and
dust that collapsed because of gravity.
Steps in the Nebular Model
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1. Young solar nebula collapses due
to gravity.
2. Solar nebula begins to rotate,
flatten, and get warmer near the
center.
3. Small “planetismals” begin to form
4. Larger “planets” begin to collect
dust and gas from the nebula
5. ACRETION – smaller planetismals
collide with the larger “planets”
causing them to grow
6. Remaining dust and gas are
eventually removed…leaving planets
around the sun
7. A NEW SOLAR SYSTEM IS
FORMED!
The Big Bang Theory
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The theory that all matter and energy in
the universe was compressed into an
extremely small volume that 10 to 20
billion years ago exploded and began
expanding in all directions.
Red Shift and Blue Shift
The Doppler Effect
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Based on wavelengths of light.
Longer wavelengths show red shift
Shorter wavelengths are blue shift
Red Shift relates to the movement of objects
away from the observer (our universe has red
shift so it is believed to be expanding)
Blue shift relates to the movement of objects
towards the observer
Galaxies
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Contain millions to billions of stars
Distances between galaxies are extremely
large.
3 Types of Galaxies – Spiral, Elliptical, and
Irregular
Spiral Galaxies
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Have spiral arms
made of gas, dust,
and stars.
Example: Milky Way
Galaxy
Elliptical Galaxies
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Have no spiral
arms and are
egg shaped.
They contain
mostly older
stars.
Irregular Galaxies
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Lack regular shapes
and do not have a
well-defined
structure
Stars: Life and Death
Chapter 20
Stars
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A large celestial body that is composed of
gas and emits light
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The SUN is a typical star that is just closer to
earth than other stars
The Greeks grouped stars into shapes called
constellations
Core temperature is more than 15 million
Kelvins
Nuclear Fusion in Stars
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Takes place in the core of the star
Combines Hydrogen atoms fusing together
because of high temperature and pressure
Energy from fusion is released as radiation
and convection through the star layers
Light travels at 3 x 108 m/s
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From the sun to the earth it takes 8 minutes
Brightness
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Depends on the star’s temperature and
distance from earth
Sirius – brightest star in the night sky
Star Color
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Related to its temperature
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Hotter objects glow brighter and have shorter
wavelengths
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Cooler objects have less intense color and have
longer wavelengths
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(closer to blue)
(closer to reds)
The sun appears yellow because the peak
wavelength of the sun is near the color yellow
…Yellow also corresponds to a temperature near
6000 kelvin
The Life Cycle of a Star
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Stars appear different when they are in
different stages of the life cycle
Stars are born, they develop, and they die
Stars are “born” from a NEBULA (cloud of
gas and dust)
The SUN is thought to be in middle age
and has about 5 BILLION years left in it.
Star Life Cycle
Low Mass/Medium Mass
Star
1.
Nebula
2.
Protostar
3.
Star
4.
Red Giant
5.
Planetary Nebula
6.
White dwarf
7.
Black dwarf
High Mass Star
1. Nebula
2. Protostar
3. Star
4. Super Giant
5. Super Nova
6. Neutron star or Black
hole
A Star is Born
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Stars are formed from a
Nebula collapsing
inward and spinning
faster and faster.
The center core
increases in temperature
Nuclear forces begin the
process of fusion
And the star is turned
on
A Dying Star
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Fusion begins to slow down, pressure in
the core drops and the core will
contract…causing core temperature to
rise.
RED GIANT – A large reddish star late in
its life cycle
WHITE DWARF – a small, hot, dim star
that is the leftover center of an old star
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No longer fuses elements
Most stars in our galaxy end as white dwarfs
SuperGiant Stars
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Massive stars that evolve faster than
smaller stars
Develop hotter cores…create heavier
elements through fusion
Fuses Iron atoms right before its death
When fusion stops, the core collapses and
causes a shock wave … and causes a
bright explosion.
SuperNova
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A gigantic explosion
from the collapsing of
a massive star
Supernova explosions
cause NEUTRON
STARS or BLACK
HOLES
Neutron Star
Black Hole
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An object so massive and dense that not
even light can escape its gravity
Since no light can escape a black hole
cannot be seen directly
They have a very strong gravitational pull.
Hertzsprung-Russell Diagram
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P. 673 shows an example
Helps astronomers understand how stars change over
time
Vertical axis indicates brightness
Horizontal axis indicates surface temperature of the star
When stars are born, they appear as protostars
Position of a star changes as they go through their life
cycle
Red giants are cool and bright so they are in the upper
right
White dwarfs are faint and hot so they are in the lower
left.