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The Sun

Our local star
by

Kellina Gilbreth

on 7 March 2016

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Transcript of The Sun

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The Sun
Our Local Star
A star is any celestial body that creates enormous amounts of energy through nuclear fusion reactions.
Internal Balance
2 opposing focres are at work within a star
Gravity pulling inwards makes the star contract
Pressure pushing outwards makes the star expand
Pressure and Gravity work on each other
Pressure supports the star from falling in on itself (preventing gravitational collapse)
Gravity contains the violent explosions from blowing the star apart (preventing expansion)
Hydrostatic Equilibrium
When there is exact balance between forces. In this condition, the star neither expands nor contracts (stays the same size)
Solar Cycle
The period of 22 years in which the Sun's magnetic field rotates a full 360 degrees, causing its poles to switch.
What causes it?
The Sun has many very strong magnetic fields. Pretend the Sun has a large bar magnet going straight through its center. Now pretend the bar magnet flips. Every 11 years, the magnet completes half its cycle and lines up North to South. At that time, the Sun’s magnetic fields are less turbulent, and the Sun appears less active. When the magnetic fields line up East to West, the Sun’s rotation causes more turbulence and the Sun appears more active.
Sunspots
Sunspots appear when the Sun is more active. They are dark spots on the Sun that are colder than the areas surrounding them (sunspots are 10 thousand °F compared to the normal ~26 million °F). Sunspots are centers for solar activity, such as solar flares, spicules, and coronal mass ejections (CMEs or solar storms).
How the active Sun affects the Earth:
In general, the atmosphere and Earth’s magnetic field protect the surface of Earth. However, it may cause the following effects:
1. Causes radio signal interference.
2. May damage satellites.
3. Creates brighter and more frequent auroras.
4. Increases radiation exposure on high flying aircraft traveling over the North or South Pole.
Solar Maximum
Every 11 years, this is the time during the solar cycle when the Sun is out of line with its magnetic poles and turning, causing more magnetic and solar activity.
Solar Minimum
Every 11 years, this is the time during the solar cycle when the Sun is in line with its magnetic poles as it has completed a 180 degree reversal, causing less magnetic and solar activity.
Layers of the Sun
Core
Radiation Zone
Convection Zone
Photosphere
Chromosphere
Corona
Innermost layer and source of energy. Unimaginably high temperature, pressure and density called plasma (the 4th state of matter – the state in which protons and electrons, which normally combine, coexist freely together. It is a super-charged gas, and is used here on Earth in welding torches). The extreme temperature (27 million °F!) causes the particles to move quickly, and slam into each other, fusing them together to create new larger atoms (nuclear fusion). Photons (packets of light and heat) are created from the fusion.
Heat and light from the core is transmitted outward. The Sun is so dense (atoms so close together) in this layer that the photon can’t easily get through. It takes millions of years for it to zig-zag its way through. Temperatures are about 9 million °F.
This is the boiling layer of the Sun. Hot material rises, and cool material sinks (like a lava lamp). Since the material is already moving outward where it is hot, the photon can travel through this layer in about 10 days. Temperatures are about 3.5 million °F.
The visible surface of the Sun. Once the photon gets here, it travels through the rest of space at the speed of light (3.0 x 10 m/s or 670 million miles per hour) Considered to be the “surface.” About 10 thousand °F.
The thin layer of the Sun that emits colored light which is seen in total solar eclipses. Considered to be the inner “atmosphere.” For unknown reasons, it is hotter than the photosphere at about 26.5 million °F. This explains why sunspots (holes in the chromosphere) are colder than the surrounding areas.
This layer is much larger than the Sun itself and merges with solar wind to fill the Solar System. The lower corona, which is closest to the Sun’s surface, is 2 million °F. Temperatures rise as you get further out to about 3.6 million °F. Considered to be the outer “atmosphere” and beyond.
Star Energy
Electromagnetic Radiation
Energy created from the motion of electrically charged particles. They can travel through the vacuum of space at the speed of light (3.0 x 10 m/s).
Electromagnetic Spectrum
To help you know the order of the EM spectrum, remember:
"Raging Martians Invaded ROY G. BIV Using X-ray Guns"
Electromagnetic Spectrum Categories:
Radio
Goes through the atmosphere. Harmless to organisms. Lowest energy. Longest wavelengths.
Infrared
Goes through the upper layers of the atmosphere. Is stopped at the tropopause. Is felt as heat. Low energy. Long wavelengths.
Visible Light
Goes through the atmosphere. Is seen as light. The “rainbow” – Red, orange, yellow, green, blue, indigo, violet (ROY G BIV). Medium energy. Medium wavelengths.
Ultraviolet
Goes through the upper layers of the atmosphere. Is stopped at the ozone layer in the stratosphere. Breaks down organic molecules. High energy. Short wavelengths.
X-ray
Cannot go through the atmosphere. Is stopped at the thermosphere. Breaks down organic molecules. Higher energy. Shorter wavelengths.
Gamma
Goes through the upper layers of the atmosphere. Is stopped by the tropopause. Easily and quickly breaks down organic molecules. Highest energy. Shortest wavelengths.
Energy vs. Wavelength
Inversely proportional. Higher energy waves have the smallest wavelengths. Lower energy waves have the largest wavelengths.
Atmospheric Filtering
Different molecules in the atmosphere reflect or absorb different wavelengths.
Nuclear Reactions
Reactions involving the nucleus of an atom (protons and neutrons)
Fission
When big “fat” atoms are broken down into smaller atoms, releasing large amounts of energy. Examples: Uranium splits into random smaller atoms like Thorium and Helium. The atom bomb (enough energy to destroy a city) Real world example: A glass vase is broken into smaller random fragments.
Fusion
When little atoms are combined into bigger atoms, releasing enormous amounts of energy. Examples: Hydrogen atoms combine into helium atoms. The hydrogen bomb (enough energy to destroy a small state) Real world example: Two slices of bread combine to make a sandwich.
Radioactivy Decay
The natural process by which unstable atoms become more stable by releasing particles (neutrons or electrons). The amount of energy being released depends on the specific type of atom. Example: Uranium releases radioactive particles at a high rate. Radon releases radioactive particles at a lower rate. Real world example: An overweight person slowly losing pounds through exercise.
E=mc
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Einstein’s famous equation relating energy to mass. E is energy in joules, m is mass in kilograms, and c is the speed of light (3.0 x 108 meters per second. For example: if we could somehow turn 1 kg of mass purely into energy, it would be enough energy to keep a 100 W light bulb lit for about 30 million years! In fusion reactions, the mass of the two smaller atoms together is smaller than the total mass of the new larger atom. The difference is tied up in the energy created.
Spectroscopy
The study of light
Continuous Spectrum
A spectrum with no breaks or interruptions. When the atoms in any solid object are excited, they emit a continuous spectrum.
Emission Spectrum
When only single lines of color are seen. When elements are excited (electrically charged), they emit specific wavelengths of energy, seen as thin lines of color. The light must be observed from its source, which must be a gas. This can be used to analyze the chemical composition of stars.
Absorption Spectrum
When a continuous spectrum is broken up with missing lines of color (black lines). The light must pass through an object to be absorbed. When atoms are hit with wavelengths of energy, the atom will absorb certain wavelengths (different for each element). For example: an object that absorbs blue, green and yellow light will appear red when viewed under white light. This can be used to analyze the chemical composition of gas clouds in space.
Microwave
Goes through the upper layers of the atmosphere. Is stopped at the mesopause. Poses little harm to organisms (when unconcentrated). Low energy. Long wavelengths.
Spectra
(plural of spectrum) – the sequence of colors created from splitting white light.

Sun's Absorption Spectrum -
(tells us the composition of the Sun's atmosphere)
Gamma
X-ray
Ultraviolet
Radio
Infrared
Visible
What do objects look like in other wavelengths?
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Nuclear Reactions
Reactions involving the nucleus of an atom (protons and neutrons)
When big "fat" atoms are broken down into smaller atoms, releasing large amounts of energy.
Starts a chain reaction.
Fission
Examples:
Uranium splits into random smaller atoms like Thorium and Helium.
The atom bomb (enough energy to destroy a city)
Nuclear power plants
Space agencies are looking to power spacecrafts for deep space travel.
Atom Review
Parts of an atom:
proton (p ), neutron (n ), and electron (e ).
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H
# of particles in the nucleus (protons + neutrons)
How "fat" the atom is.
# of protons
The atom's identity.
Symbol
The atom's name.
He
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Li
6
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Na
22
11
# of neutrons is like amount of atom "fat."
The more neutrons, the "fatter" the atom and the more unstable it is.
He
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He
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He
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He
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"Skinny" Generally Stable
"Fat" Generally Unstable
n + U Xe + Sr + n
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235
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n + U Xe + Sr + n
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Example Fission Reaction:
Don't feel overwhelmed!!!
The reaction can be broken down into 2 simple equations:
1 equation on the top
1 equation on the bottom
1+235=134+100+2
0+92=54+38+0
Remember that the arrow becomes an equal sign!
When little atoms are combined into bigger atoms, releasing enormous amounts of energy.
Requires energy to start.
Fusion
Examples:
Hydrogen atoms combine into helium atoms.
The hydrogen bomb (enough energy to destroy a state)
Powers all stars, including the Sun.
Someday, cold fusion may solve all of the world's energy needs.
H + H He + n
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Example Fusion Reaction:
2+3=4+1
1+1=2+0
H + H He + n
The natural process by which unstable atoms become more stable by releasing extra neutrons or electrons.
The amount of energy released depends on the type of atom decaying.
Radioactive Decay
Examples:
Uranium releases radioactive particles at a high rate.
Radon releases radioactive particles at a low rate.
Many worlds produce internal heat by radioactive decay, including Earth.
U Th + He
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Example Radioactive Decay Reactions:
238=234+4
92=90+2
U Th + He
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Th Pa + e
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Th Pa + e
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234=234+0
90=91-1
E=mc
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E = energy in Joules (J)
m = mass in kilograms (kg)
c = speed of light in meters per second (3.0 x 10 m/s)
Albert Einstein's famous equation relating energy to mass.
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If we could somehow turn 1 kg of mass into pure energy...
E = 1 x (3.0 x 10 )
E = 9.0 x 10 J
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That's enough energy to keep a 100 Watt light bulb lit for about 30 million years!
In nuclear reactions, the starting mass does not equal the ending mass.
That "missing" mass becomes energy!
Now we will practice some problems...
Why is Fusion stronger than Fission?
Generally, there is more of a mass difference in fusion reactions than fission reactions.

More difference in mass means more energy released!
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