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Sun

Sun. enrico. hydrostatic equilibrium - the fact that pressure balances the self-gravity. the amount of energy generated equals the amount radiated away. Questions historical . What is the sun fuel? Why is not a coal sphere burning? Where does all that energy come from?

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Sun

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  1. Sun enrico

  2. hydrostatic equilibrium - the fact that pressure balances the self-gravity

  3. the amount of energy generated equals the amount radiated away

  4. Questions historical • What is the sun fuel? • Why is not a coal sphere burning? • Where does all that energy come from? • How did the sun affects our climate on the earth • How much fuel is burned every day • Which Is the future of the Sun • Is it possible to reproduce that on the earth? • How can you connect the end of the Sun with the end of human life?

  5. What is the sun fuel? some early scientific ideas: • In the late 1700s, the philosopher Immanuel Kant calculated that if the sun generated energy chemically (such as by burning coal), it could only last for a few thousand years. • In the late 1800s Hermann von Helmholtz calculated the energy that might be generated if the sun was still contracting under gravity, then would only last about 20 million years. • Energy emitted by friction of its gas masses or derived from gravitational potential energy released as it continuously contracted • Nuclear fusion was first proposed as the source of solar energy only in the 1930s

  6. How did the sun affects our climate on the earth • The faint young sun paradox describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the sun's output would be only 70% as intense during that epoch as it is during the modern epoch. • some form of super greenhouse environment early in the Earth's history.

  7. How old is the light that comes to us from the sun • The core's gas is about one hundred times denser than most metals. Since the core is this dense, it is hard for rays to leave. When gamma rays are released by fusion, they continue to collide with other atoms. Due to this, it takes the gamma rays almost thirty thousand years to reach the sun's surface! This means that the light that we receive on Earth was created thousands of years ago.

  8. Thermonuclear Fusion • This fusion reaction in the Sun is called the proton-proton chain (the same process that powers H-bombs). It has the following four stages

  9. 1st step • The first step involves the fusion of two hydrogen nuclei 1H (protons) into deuterium2H, releasing a positron as one proton changes into a neutron, and a neutrino. 1H + 1H → 2H + e+ + νe with the neutrinos released in this step carrying energies up to 0.42 MeV. This first step is extremely slow, because it depends on the weak interaction to convert one proton into a neutron. In fact this is the limiting step, with a proton waiting an average of 109 years before fusing into deuterium.

  10. 2nd and 3nd step • The positron immediately annihilates with one of the hydrogen's electrons, and their mass energy is carried off by two gamma rayphotons. e+ + e− → 2γ + 1.02 MeV • After this the deuterium produced in the first stage can fuse with another hydrogen to produce a light isotope of helium, 3He: 2H + 1H → 3He + γ + 5.49 MeV

  11. 4th step 3He +3He → 4He + 1H + 1H + 12.86 MeV • The complete pp I chain reaction releases a net energy of 26.7 MeV. The pp I branch is dominant at temperatures of 10 to 14 megakelvins (MK). Below 10 MK, the PP chain does not produce much 4He.

  12. How much mass the sun is burning • The rate at which the Sun produces energy is equal to the rate at which it emits energy from its surface (its luminosity), which is around 3.8 x 1026 Watts. Plugging this into the above formula tells us that the Sun loses around 4,200,000,000 kilograms every second!

  13. Sunspots • Sunspots pairs are due to magnetic flux tubes on the surface of the Sun. They carry energy away causing the surface to be cooler (1800 degrees cooler) than the surrounding material, thus their darker appearance. The number of sunspots per year varys with an 11 year cycle and the peaks are associated with times of high solar activity (many flares and solar storms).

  14. Is it possible to reproduce that on the earth? • Yes , they do it ever day at Cern • It is also available in a much less peaceful form as an H bomb

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