ANSWERS: 1
  • 1) "Sunlight is the primary source of energy to Earth. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. The solar constant is equal to approximately 1,370 watts per square meter of area at a distance of one AU from the Sun (that is, on or near Earth). Sunlight on the surface of Earth is attenuated by the Earth's atmosphere so that less power arrives at the surface—closer to 1,000 watts per directly exposed square meter in clear conditions when the Sun is near the zenith." "Through most of the Sun's life, energy is produced by nuclear fusion through a series of steps called the p–p (proton–proton) chain; this process converts hydrogen into helium. The core is the only location in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core. All of the energy produced by fusion in the core must travel through many successive layers to the solar photosphere before it escapes into space as sunlight or kinetic energy of particles." "The high-energy photons (cosmic, gamma and X-rays) released in fusion reactions are absorbed in only few millimetres of solar plasma and then re-emitted again in random direction (and at slightly lower energy)—so it takes a long time for radiation to reach the Sun's surface. Estimates of the "photon travel time" range from as much as 50 million years[12] to as little as 17,000 years.[13] After a final trip through the convective outer layer to the transparent "surface" of the photosphere, the photons escape as visible light. Each gamma ray in the Sun's core is converted into several million visible light photons before escaping into space. Neutrinos are also released by the fusion reactions in the core, but unlike photons they rarely interact with matter, so almost all are able to escape the Sun immediately." Source and further information: http://en.wikipedia.org/wiki/Sun 2) "Sun's energy comes from fusion processes deep in the solar core. Here the temperature reaches 10,000,000°, hot enough to fuse four hydrogen atoms into one helium atom. Unlike fusion energy research on Earth, where magnetic fields confine the plasma, Sun is able to confine the plasma through the tremendous gravitational forces. Outside of about 1/4 of Sun's radius the fusion processes stop, and we reach a region called the radiation zone. The energy generated in the core, in the form of electromagnetic radiation, slowly leaks out towards the surface. In fact, it takes about a million years for aphoton (a light particle) to travel from the core across the radiation zone. The outer 1/4 of Sun is the convection zone. Here the dense plasma fluid, like very hot sticky syrup, slowly circulates between the radiation zone and the surface. This stirring motion brings energy from the solar interior to the photosphere." "The photosphere is the name for Sun's surface; it's the point where the light finally escapes. Sort of like looking into a very dense fog, and the photosphere is the deepest layer you can see to. At the photosphere the temperature of Sun has cooled from 10 million degrees to 5,600 degrees. Then, something remarkable happens. One would expect that as we move away from Sun's surface the temperature would get cooler – like moving away from a campfire. But exactly the opposite happens: the temperature of the solar atmosphere increases! The solar atmosphere is broken up into three regions: the chromosphere, the transition region and the corona. The figure shows the different regions and how their temperature changes as we go up in the solar atmosphere. The temperature of the atmosphere rises from 5,600° to over 1 million degrees in the corona."

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