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The Sun Our Star Warm Up 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 1. 2. 3. 4. 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 1. 2. 3. 4. 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 1. 2. 3. 4. 5. 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 1. 2. 3. 4. 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 1. 2. 3. 4. 5. 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 1. 2. 3. 4. 5. 6. 7. 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 1. 2. 3. 4. 5. 6. 7. 8. 9. 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 1. 2. 3. 4. 5. 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 1. 2. 3. 4. 5. 6. 7. 8. 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 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 1. 2. 3. 4. 5. 6. 7. 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.