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ast review from someone else - What process creates energy...

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What process creates energy in the Sun? Nuclear fusion usually H to He Why does the Sun’s size remain stable? The Sun’s size remains stable because it is in gravitational equilibrium—the outward pressure of hot gas balances the inward force of gravity at every point within the Sun. How did the Sun become hot enough for fusion in the first place? As the Sun was forming, it grew hotter as it shrank in size because gravitational contraction converted gravitational potential energy into thermal energy. Gravitational contraction continued to shrink the Sun and to raise its central temperature until the core became hot and dense enough for nuclear fusion. What do we mean by the “surface” of the Sun? We consider the photosphere to be the surface of the Sun because light can pass through the photosphere but cannot escape from deeper inside the Sun. Thus, photographs of visible light from the Sun show us what the photosphere looks like. Know the zones of the Sun. radiation and convection Why is energy produced in the Sun at such a steady rate? The fusion rate is self-regulating like a thermostat. If the fusion rate increases for some reason, the added energy production puffs up and cools the core, bringing the rate back down. Similarly, a decrease in the fusion rate would allow the core to shrink and heat, bringing the fusion rate back up. Why was the Sun dimmer in the distant past? Although the fusion rate is steady on short time scales, the fusion rate gradually increases over billions of years, increasing the Sun’s luminosity. The increase occurs because fusion gradually reduces the number of individual nuclei in the solar core — because 4 hydrogen nuclei are fused to make just 1 helium nucleus — which causes the core to shrink and become hotter. Describe the sunspot cycle. Sunspots occur where strong magnetic fields trap and isolate gas from the surrounding plasma of the photosphere. The trapped gas cools, so that sunspots became cooler and darker than the rest of the photosphere. Sunspots therefore tend to occur in pairs connected by a loop of magnetic field, which may rise high above the surface as a solar prominence. The magnetic fields are twisted and contorted by the Sun’s differential rotation, and solar flares may occur when the field lines suddenly snap and release their energy. Cycle repeats every 11 years because the Sun's magnetic field switches polarity. What is the solar wind? When magnetic field lines break, they release the charged particles into space. This so-called solar wind escapes through the coronal holes.
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How does solar activity effect humans? Particles ejected from the Sun by solar flares and other types of solar activity can affect communications, electric power delivery, and the electronic circuits in space vehicles. It is not clear how solar activity affects the Earth’s climate. What is the difference between Luminosity and Apparent Brightness
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ast review from someone else - What process creates energy...

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