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-------------------- 2489 - SUN - facts you won’t believe?
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- Yes, the interior of the Sun is hot, 13,600,000 degrees Kelvin. By contrast, the Sun’s surface is 5,785 Kelvin. The temperature of the Sun is generated by 4 protons fusing together. We have all learned that the fusion in the Sun is converting hydrogen into helium. This is true, but it is not hydrogen and helium gas as we know it. It is ionized plasma.
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- The temperature in the Sun is hot enough to separate all electrons from their nuclei. The electrons become free negative particles and the nuclei become free ionized, positive particles. This state of matter is called a “plasma“.
- Temperature is the average kinetic energy, or energy of motion, or constantly vibrating particles, or atoms. When the temperature is high enough and the vibrations are energetic enough the electromagnetic force that normally holds the electrons and protons together is overpowered. The two get separated.
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- The positive and negative electric charges are an attractive force. When the attractive force is overpowered they separate and the free electric charges go there separate ways. The hydrogen nuclei is a single free proton of positive charge. The nuclei of helium is 2 protons and 2 neutrons, with a positive charge of 2. Each neutron is a fused proton and electron and a neutrino. By weight it is another proton but by electric charge it is neutral.
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- In the Sun’s core, several other combinations of protons are fused together but these other nuclei are unstable and radioactive. They soon decay into other elements. However, the element of helium is very stable and it makes up 25% of the Sun. This is easy math: 75% is hydrogen with 1 proton. 25% is helium with 4 protons.
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- Each step of the fusion processes releases energy in the form of radiation. The highest energy electromagnetic radiation is called Gamma Rays. The Gamma Rays take years and years of bouncing off particles, being absorbed and re-emitted as lower energy radiation as they make their way to the surface.
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- It can take 17,000 to 1,000,000 years for each Gamma Ray to make it to the surface. When they finally make it they are much lower energy and are released into space as ultraviolet, visible and infrared radiation at a temperature of 5,785 Kelvin.
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- So, how can I state that the Sun is not so hot? It is in the details. The Sun’s core converts 3.4*10^38 protons into helium nuclei every second. There are a total of 8.9*10^56 protons in the Sun. 8.9*10^56 protons in the Sun. At 3.4*10^38 protons per second. That would exhaust the protons in 2.6*10^18 seconds. There are 3.156*10^7 seconds in a year. That is 83 billion years. Obviously the Sun will not burn at a constant rate. The rate will increase as the Sun gets older because it will last only another 5 billion years.
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- Every second there is a 1 proton to 4 proton fusion converting some of the mass into energy according to E=mc^2. The Sun converts 4,260,000 tons of matter into 3.83*10^26 watts of energy every second. It is not that the Sun is so HOT, it is that the Sun is so BIG.
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- 99.85% of all the mass in the Solar System is located in the Sun. At the Sun’s core the energy conversion is 0.3 microwatts per cubic centimeter (0.3*10^-6 w / cm^3). A cubic centimeter is about the size of a sugar cube.
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- A burning candle produces heat at 1,000,000 microwatts/cm^3. That is a million times more heat production from a candle than from a cubic centimeter at the Sun’s core. The human body produces about 1,200,000 microwatts per kilogram. That is 1.2 watts per kilogram. If you weigh 183 pounds, 83 kg, your body heat is about the same as a 100 watt light bulb. That is the reason you show up so bright on an infrared camera.
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- So, the Sun is not so HOT. If we were to use the Sun’s plasma to create a 1 gigawatt electric power plant here on Earth we would need to use 170 billion tons of plasma. That amount of plasma would occupy a volume of one cubic mile.
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- Fusion power plants might be practical here on Earth someday but they will have to operate at much higher temperatures than even the Sun. Temperatures so hot there is nothing that can contain them.
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- Fusion experiments are trying to develop magnetic and laser containers for the hot plasma. But, to date we have not been successful in developing a practical fusion reactor. That is fusing lighter elements into heavier ones. All the nuclear reactors in use today are fission reactors. Breaking heavy elements ( uranium ) into lighter ones.
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- The Sun is not so HOT, it is so BIG. 99.85% of all the mass in the Solar System is located in the Sun. That leaves 0.15% of the mass for all the planets, asteroids, comets and space dust that we are made of.
- The surface temperature of the Sun is 5,875 degrees Kelvin. But, the atmosphere above the surface is 1,000,000 Kelvin. The atmosphere near the surface is called the photosphere.
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- The photosphere is tens to thousands of kilometers thick ( 6 to 300 miles thick). The particle density of the photosphere is 10^23 particles / cubic meter. That is a very thin atmosphere. It is 1% the particle density of the Earth’s atmosphere at sea level, which is 2*10^25 / m^3.
- Above the photosphere, which is the optical surface, is the Corona which we only get to see during a solar eclipse. The Corona is very hot, 1,000,000 Kelvin and it is a mystery how it can be so hot. The surface of the Sun is 5,875 K.
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- How can the atmosphere far above it be 1,000,000 K. What could possible be heating it up? The total volume of the Corona surrounding the Sun is much larger than the Sun. The particle density is much less at 10^15 particles per cubic meter.
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- A theory as to how the Corona heats up is that it is the Sun’s magnetic fields providing the energy. To explain this we will need to learn how the Sun creates its magnetic fields. It is done much differently on the Sun than on the Earth.
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- Above the Sun’s core and from about 20% to 70% of the Sun’s volume the thermal radiation is so intense that thermal “convection” to transfer heat can not operate. Heat is being transferred by proton ions continually absorbing and re-emitting photons.
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- It is a very slow travel outward with all this bouncing around taking a photon anywhere from 17,000 to 1,000,000 years to reach the surface. However, above the 70% point from the core the solar plasma is no longer dense enough, or hot enough, to transfer heat by radiation. This is where thermal convection begins.
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- The thermal convection occurs in thermal columns, almost like chimneys, that carry hot plasma to the surface where it releases light radiation, cools, and plunges backward down its edges to the base of the convection zone again. The plasma heats up again and begins to rise repeating the process over and over again.
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- This thermal convection has the effect on the surface as being granules. The columns of material rise and sink back at the granule edges. The effect of these rising and falling charged plasma particles is to create a circular electric current. The circulating current in turn creates a powerful magnetic field.
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- The next part of the theory depends on the fact that the Sun rotates faster at the equator than it does at the poles. Plasma moves around the equator in 25 days. Plasma at higher latitudes rotates in 35 days.
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- The different rotation rates cause the magnetic field lines formed by the granules to become twisted over time. Field line loops snap and reconnect in their north-south connections releasing enormous magnetic energies.
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- These magnetic storms when sever enough appear as sunspots or solar prominences. The total twisting action creates an overall solar dynamo cycle repeating every 11 years. Every 11 years the magnetic activity peaks and the north-south orientations of the Sun’s magnetic fields reverse themselves.
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- This continuous magnetic activity occurring above the surface of the Sun is what causes the 1,000,000 Kelvin temperatures to occur in the Corona. This is still a theory and the exact mechanism and a complete understanding of this phenomena remains a mystery.
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- The 11 year cycle of sunspot activity has been recorded for the last 250 years. Sunspots usually exist as pairs with the opposite polarity. The polarity of the leading sunspot alternates every 11 year cycle. It will be a north magnetic pole in one 11 year cycle leading the way around the Sun, then a south magnetic pole in the next 11 year cycle.
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- The sunspot activity, and therefore the Sun’s magnetic activity, has significant influence on the Earth’s climate. When solar activity is at a minimum the Earth tends to have cooler temperatures. When solar activity is maximum the Earth has hotter temperatures.
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- In the 1600’s the solar activity was particularly low for several decades. Not many sunspots were seen. During that period the Earth experienced the Little Ice Age. Europe in particular documented very cold temperatures. Tree Rings have indicated lower than average temperature throughout the globe during the Little Ice Age.
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- Other Solar cycles, beyond the 11 year cycle, have shown fluctuations in the Sun’s activity every 41,000 years and every 100,000 years. When all of these activity cycles line up we could experience an extreme temperature variation on Earth.
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- Today we think we are entering a period of lower Sun activity and cooler temperatures. This might compensate for the opposite greenhouse gas effect created by human use of fossil fuels in global warming.
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- But, what happens when in 11 years the cycles line up with global warming creating an even greater extreme in temperatures. Understanding the Sun’s cycles and their effects on Earth should be a major concern and study for the students in today’s science classes. Our lives depend on it.
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See these Reviews for more about the Sun.
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- 1720 - lists 10 more Reviews including: “ How do we know the age of the Sun?’
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- 533 Why the Sun will become a White Dwarf star.
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- 382 Our Closet Star
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- 383 Could our Sun be a variable star? Sunspots.
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- November 19, 2019 2489 834 833
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