Transcript 8 The Sun - Journigan-wiki

The Sun
Our Star
Warm Up
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Summarize what you remember from the
film “The Elegant Universe” in a few
paragraphs. Is string theory a “theory” or
a “philosophy?” Why or why not?
Warm Up-03/06/13
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Describe stage 1 on the proton-proton
chain, products and remnants.
Describe stage 2 on the proton-proton
chain, products and remnants.
Describe stage 3 on the proton-proton
chain, products and remnants.
Describe stage 4 on the proton-proton
chain, products and remnants.
Warm Up
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To make the math work out correctly,
how many dimensions are required in the
Universe?
What is a membrane or “brane” to a
string theorist?
What happens (theoretically) when
membranes collide?
What is the purpose of the supercollider
in CERN?
Warm Up
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What historical event occurred that
provided the catalyst to create the
Mercury space program.
Who was the first man is space?
Who was the first American in space?
Who was Chuck Yeager and what did he
do that made him famous?
Who was the last Mercury
Warm Up
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How far away is the Sun?
How much more massive is the Sun than
the Earth?
What are the three layers of the Sun?
What are the two zones of the Sun?
Warm Up
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6.
What is the northern-most constellation at midnight
tonight?
What was the eastern-most constellation on Christmas
at 10:00 pm?
What was the southern-most constellation on New
Years Day at 8:00 pm.
What constellation is located at the center of your
planesphere?
What was the northern-most constellation on your past
birthday at noon.
Name 3 constellations that are visible tonight at 9:00
pm.
Warm Up
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What powers the Sun
What does the Sun do, besides give off heat
and light?
What are the Sun’s two atmospheric layers?
What happens in the radiative zone of the Sun?
What happens in the convective zone of the
Sun?
How old is our Sun?
What is hydrostatic equilibrium?
Sun Webquest
http://jn016.k12.sd.us/sun_webquest_sites.htm
1. How old is the sun?
2. What is the temperature of the sun? (in Fahrenheit)
3. How far away is the sun from the Earth? ( Tell us in miles &
kilometers)
4. What are the layers of the Sun? Give a brief description of the
major layers AND include a labeled picture of our Sun's layers.
5. What is the chemical make up (elements)of the sun?
6. What are the percentages of those chemicals?
7. What are sunspots?
8. When were sunspots first discovered and who discovered them?
9. How are magnetic storms on Earth related to sunspot activity?
10. How does the number of sunspots change over time?
11. Describe what causes each of the following: prominences, solar
flares, solar wind, CME’s (coronal mass ejections)
12. How does the sun get its energy?
13. What is nuclear fusion?
14. How can you safely observe the sun?
Our Star
Our star, the Sun, is a dazzling luminous
ball of burning gas one hundred times the
radius of the Earth. Viewed normally, the
Sun seems peaceful and regular, but viewed
through a telescope, the Sun is a teaming,
explosive place where fountains of heated gas
leap 100’s of miles above the surface.
Scale of the Solar System
The Sun dwarfs the rest of the solar system.
100 times the radius of the Earth, the Sun
has a mass 300, 000 times that of our planet.
Solar Facts
The Sun is about 93 million miles from Earth.
Surface gravity on the Sun is about 30 times that
felt by a body on Earth.
The Sun’s surface temperature is about 5,800 K.
The Sun’s core temperature is about 15 million K.
The Sun’s core is 100 times denser than water.
Solar Facts
The mass of the Sun is about 333,000 times
the mass of the Earth.
It is estimated that the Sun releases about 4
X 1026 watts into space from its surface.
The Sun is composed of 71% hydrogen, 21%
helium and 2% heavier materials such as
carbon and iron.
The Sun’s Interior
The Sun is
composed of several
layers:
1. The Photosphere
2. The Chromosphere
3. The Corona
And two distinct zones
1. Radiative Zone
2. Convective Zone
The Photosphere
The outside of the Sun is relatively
transparent, however, with increased depth
the Sun becomes opaque. The cause of this is
that at a certain depth the weight of the
overlying gas crushes the underlying gases
together so tightly that they can not be seen.
The photosphere
makes up the portion of
the Sun that we cannot see.
Radiative Zone
Near the Sun’s core, energy is moved by
radiation carried by photons (remember
those?). This area is called the radiative zone.
Because the gas there is so dense, before most
photons travel an inch, they are absorbed by
an atom and stopped. The photon will be reemitted later only to be stopped by another
atom.
Radiative Zone
Like traffic stuck at a light, the photons are
delayed. This delay is quite long, to the
extent that the sunlight we see today was
generated about 16 million years ago.
The Convection Zone
Just below the photosphere where the gas is
cooler and less transparent, the flow of
energy is slowed. In this region, photons are
even less effective at moving energy.
The Convective Zone
Convection currents carry energy from this
region toward the Sun’s surface. These are like
similar currents within the Earth and the gas
giant planets.
This is why the
region is called the
convection zone.
The Convective Zone
While we can’t see these gases, we can infer
their motion by observing tiny bright
regions surrounded by darker areas that
appear on the surface. These are called
granules. These granulations form from
bubbles of rising hot gas.
The Convective Zone
These rising bubbles burst and cool,
emanating heat and light into space. The
cooling gases subside and turn dark,
creating the dark edges that surround each
granule.
The Convection Zone
Using the Doppler Effect, scientists have
measured how rapidly this granules rise and
found that their average speed is about one
kilometer per second (km/s).
The Sun’s Atmosphere
Scientist refer to the very low density gases
above the Sun’s photosphere as the Sun’s
atmosphere. This atmosphere, like the
Earth’s, becomes gradually thinner the
farther it extends into outer space.
The Sun’s Atmosphere
You’d think with the density of the gases
decreasing, that the temperature would
decrease too, but just the opposite occurs.
Because they are more easily heated at higher
altitudes, the gases burn with great
intensity. The temperature immediately
above the photosphere has an average
temperature of several million Kelvin.
The Sun’s Atmosphere
The Sun’s atmosphere consists of two major
divisions; the chromosphere lies directly
about the photosphere and it is the Sun’s
lower atmosphere.
Chromosphere
The chromosphere consists of millions of jets
of hot gas called spicules. Spicules are
generally thousands of kilometers long. The
chromosphere’s red color comes from the
strong emission spectrum of hydrogen.
The Corona
The outer-most layer of the Sun’s atmosphere
is the corona. The temperature in the
chromosphere is about 4,500 K, but only
about 2,000 km’s higher the temperature
soars to 50,000 K.
The Corona
Since rising into the corona from the
chromosphere, the temperature of a gas may
have climbed 1 million degrees. Despite its
high temperatures, the corona has very little
energy due to its lack of density.
Stellar Equilibrium
Our Sun, like all healthy stars, exists in a state of
equilibrium. Gravity pulls in the Sun’s mass
toward its center with tremendous force. But, the
Sun also pushes out (with heat and energy) with
great force. It pushes out exactly as hard as gravity
pulls it in.
This balance of forces
maintains the stability
of our star. This is known
as hydrostatic equilibrium.
Warm Up
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What is hydrostatic equilibrium?
Why does the Sun have a limited life time?
What does heat create?
What is a granule?
What is a spicule?
The earliest astronomers thought that the Sun was
fueled by what? And would last how long?
Who was the first dude to think that the Sun was
power by subatomic energy?
Who was the first dude to confirm it?
What did Einstein have to do with all this?
Warm Up-10/16/12
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What is hydrostatic equilibrium?
Why does the Sun have a limited life
time?
What does heat create?
What is a granule?
What is a spicule?
Stellar Equilibrium
Equilibrium comes at a price, however. In
order to maintain its outward force, the Sun
has to consume itself as fuel. As an area of
limited resources, the Sun will one day
exhaust its fuel supply and die. Every
second the Sun consumes 4 million tons of
itself.
Pressure in the Sun
The pressure that counter-balances gravity’s
forces comes from the rapid motion of atoms.
For a better understanding of the Sun, we
must understand pressure.
Pressure cooker
Pressure in the Sun
Pressure comes from atoms and
molecules colliding. The more you
compress something, the closer its atoms
and molecules are and the more
collisions that occur. This is called
density. This creates pressure.
Pressure in the Sun
The more you heat something, the faster
its atoms and molecules move and the
more violently they collide. This creates
pressure as well.
The Ideal Gas Law
We’ve established the relationship between pressure
and temperature and density. Stated formally, it
is known as the Ideal Gas Law and it states:
Pressure = Density X Temperature X some constant
Scientists have calculated that given the mass of the Sun
and its tremendous gravitational pull inward, its
internal temperature must be about 15 million K to
remain at equilibrium.
Warm Up
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Define the following: The Photosphere, The
Chromosphere, The Corona, Radiative Zone
and Convective Zone
What is the diameter and mass of the Sun
relative to Earth?
What are granules and how do they form?
What are the two layers of the Sun’s atmosphere?
What is stellar equilibrium? Why is it
important?
According to the Ideal Gas law, what effects
pressure?
What is the cost to the Sun for maintaining its
equilibrium?
What is a spicule?
Powering the Sun
Energy created by the Sun is eventually lost
into outer space by heat and light. If the
Sun did not replace this lost heat, the
pressure pushing the Sun out would
diminish until the Sun eventually collapsed
under its own gravity.
Powering the Sun
Many early astronomers believed that the
Sun burned conventional fuels such as coal.
The supply of coal would have been exhausted
after about 10,000 years.
Powering the Sun
In the late 1800’s, Lord Kelvin (English) and
Hermann Helmholtz (German)
independently proposed that the Sun was not
at hydrostatic equilibrium, but was actually
slowly collapsing.
The Sun could only
sustain itself for
about 10 million
years doing this.
Powering the Sun
In 1899, T.C. Chamberlin suggested that
subatomic energy might power the stars, but
could offer no explanation as to how.
Powering the Sun
It was not until 1905 that Albert Einstein
proposed that energy might actually come
from mass with his equation E=mc2.
Einstein’s Equation
E = mc2, where E is energy (joules), m is
mass and c is the speed of light (3X108
m/s2). The amount of energy that is
available from nuclear reactions is
staggering. One gram of mass (one paper
clip) could be converted into 20 kilotons
worth of
energy.
Follow Up Work
In 1919, Arthur S. Eddington showed that
converting hydrogen to helium could provide
enough energy to power stars including our
Sun.
Follow Up Work
Physicists Hans Bethe and Carl von
Weizsacker proposed that the Sun produced
its energy by the process of nuclear fusion.
Nuclear Fusion
Under normal conditions, hydrogen nuclei
repel each other due to similar electrical
charges, but under conditions of extreme heat
when these atoms collide their nuclei are
driven extremely
close to each other.
The Proton-Proton Chain
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Hydrogen fusion takes place in three stages
called the proton-proton chain.
The Proton-Proton Chain
Stage 1: Two hydrogen nuclei collide to
form a hydrogen isotope called 2H. This
process converts one proton into a neutron
and releases a positron (e+) and a
neutrino (v).
The Proton-Proton Chain
Step 2: The 2H nucleus collides with a 1H
nucleus to make an isotope of 3He. This
process releases energy in the form of
gamma rays (g).
The Proton-Proton Chain
Stage 3: Two 3He nuclei collide together and
fuse. This forms two separate particle types,
4He and two 1H nuclei.
Searching for Neutrinos
During Stage 1 of the
proton-proton chain, we
saw that the Sun
generates neutrinos in
the fusion process.
Scientists have
searched for these
neutrinos as evidence
of the fusion process in
the Sun.
Searching for Neutrinos
Scientists calculated the amount of
neutrinos that they expected to be generated
by the Sun. Because neutrinos have so little
mass, they can penetrate anything and are
very hard to detect, like bullets shooting
through tissue paper.
Searching for Neutrinos
The first neutrinos detectors were built in the late
1970’s, one in Japan and one in the United States.
They were built deep under ground for shielding
from
cosmic rays.
The detectors were
filled with a solution
like heavy water.
Searching for Neutrinos
When a neutrino
passes through the
solution and
collides with a
neutron, it creates a
flash of light from
an electron. Light
sensors count the
flashes.
Searching for Neutrinos
Another thing that makes neutrinos hard to
detect in that they come in three separate
structures (called a, b and g-neutrinos).
They transform themselves as the travel.
Initially, scientist only detected a third of
the neutrinos that they expected to find.
They could only detect one of the types.
Summary of Point
Not until very recently have we discovered
evidence of how our Sun actually
manufactures its energy. We didn’t even
have a good guess until the 1950’s. There is
still a lot that we do not know about our star!
Solar Magnetic Activity
The Sun’s magnetic field gives rises to
several solar phenomenon. These include
Solar prominences, Solar prominences, Sun
spots and the Earth’s aurora borealis.
Solar Phenomenon
Solar prominences: Are
magnetic disturbances
in the Sun’s atmosphere.
Gigantic plumes of hot
gas from the lower
chromosphere jump into
the corona. Prominences
form as cooling gas
trapped within the Sun’s
magnetic field. They are
usually seen arcing
between sunspots.
Solar Phenomenon
Solar flares: These are
not well understand
but are thought to be
the Sun’s magnetic
field being twisted by
hot, rising gas. The
fields can only be
twisted to much, before
they readjust, forming
a flare. Like a rubberband toy.
Solar Phenomenon
Sun spots: charged
particles are attracted
to the Sun’s magnetic
field. These particles
spiral down the
magnetic field lines
and slow the ascent of
heat. This creates
colder areas on the
surface. These cool,
black areas are known
as sunspots.
The Solar Wind
As the Sun burns, it releases heat and
energy in several forms. One of these forms
is as charged particles. These particles
streak across space at the speed of light.
They strike the Earth’s magnetic field and
glow in an eerie phenomenon known as the
aurora borealis.
Solar Phenomenon
Warm Up
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What is the source of the Sun’s energy?
Describe the three stages of the protonproton chain.
What is a solar prominence? How do they
occur?
What is a solar flare? How do they occur?
What is a sun spot? How do they occur?
What is a neutrino? Why are scientists
looking for them so hard?
What is the aurora borealis?
Writing Assignment
Step 1: Within your group, discuss current issues in science. Focus on
this question, “Is science destructive”?
Step 2: On a piece of paper, please write:
Paragraph 1: State three examples that you discussed and tell why they
are relevant to the question.
Paragraph 2: Explain your personal position concerning the question,
“Is science destructive”?
Solar Cycles
We have lots of solar cycles.