Chapter 14/5 – Flashcards
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What two forces are balanced in gravitational equilibrium?
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1. the inward pull of gravity 2. the outward push of internal gas pressure. As the weight increases in the lower layers of the sun, the pressure also increases (to maintain balance)
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The sun's "energy balance"
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-balance between the rate fusion releases energy in the core and the rate the suns surface radiates this energy into space
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Briefly describe the distinguishing features of each of the layers of the Sun.
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Outside to inside: Solar wind, Corona, Chromosphere, Photosphere and Sunspots, Convection Zone, Radiation Zone, Core.
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Solar wind
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the gas and particles ejected from the Sun
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corona
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the loose atmosphere around the sun
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chromosphere
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a more dense but less hot atmospheric region that has small spikes of gas jet up into it from the surface
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photosphere
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the visible surface of the Sun, and the region where sunspots develop
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sun spots
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Sun spots are cooler regions which have intense magnetic fields.
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Convection zone
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where the energy from the core is brought upwards via convection (the rising of hotter gases and the falling of cooler gases.)
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The radiation zone
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is where energy travels to the convection zone from the core primarily via photons.
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The Core
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is where fusion happens.
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What is the difference between nuclear fission and nuclear fusion?
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Fission: the process of generating energy by breaking apart large nuclei. ex. Nuclear power plants Fusion: where energy is produced by combining two or more small nuclei to make a larger nucleus. ex. the Sun
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Why does nuclear fusion require high temperature and pressures?
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-When the nuclei collide, they do so at very high speeds (and high temps) -this allows the strong forces the opportunity to bind them. -If they collide at low speeds, the repulsion force will dominate and prevent the collision (and fusing) of nuclei. -The pressure needs to be high so that the hot plasma is contained in the core and doesn't diffuse into space
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What is the overall nuclear fusion reaction in the Sun?
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-Nuclear fusion is the source of all energy the Sun releases into space. -The Sun fuses hydrogen at a steady rate, thanks to a natural feedback process that acts as a thermostat for the Sun's interior (p-p chain). -Solar energy production remains steady because the rate of nuclear fusion is very sensitive to temperature.
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Proton-proton chain
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-When two protons fuse to make a hydrogen nucleus, which the fuses with a proton to makes a nucleus of helium. -Two helium 3 nuclei fuse and form helium-4, releasing two protons in the process.
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Briefly describe how a natural solar thermostat keeps the core fusion rate steady in the Sun.
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-rate of fusion: temperature-sensitive -Most of the energy in the sun is produced by the p-p chain, fusing a hydrogen nucleus with a proton -It forms helium and releases radiation. -The gravitational pull in the sun is balanced by the radiation pressure, which keeps the temp constant
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Describe how energy generated by fusion makes its way to the Sun's surface. How long does it take?
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-Most of the Sun's energy starts in the core. -Energy moves from core to radiation zone as photons. -The photons bounce around until they reach the top of the radiation zone -temp cools so plasma can absorb the photons. -Works it way up through the convection zone -The hotter gases drift up until the energy can escape to the photosphere or surface of the Sun. -It takes hundreds and thousands of years
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How do mathematical models help us learn about conditions inside the sun, and what gives us confidence in models?
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-We use math & physics laws to imagine what the Sun is like internally. -We can then compare the results of the model's internal conditions (temperature, pressure, and density) to the results of real world experiments (surface temperature, radius, luminosity, age, etc) -Then we know whether the model is correct or not by how well the predict results match the real world results.
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Solar neutrino problem
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-Early attempts to detect neutrinos only turned up a third of the amount required by predictions based on models of the Suns core. -Discovered there are three types of neutrinos and that early detectors only picked up one.
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neutrinos
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sub-atomic particles that can pass through most matter without interacting
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If fusion in the solar ceased today, worldwide panic would break out tomorrow as the Sun began to grow dimmer.
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False. -It takes about a million years for light to get from the core to the surface, so we wouldn't notice anything for a while.
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I wear a lead vest to protect myself from solar neutrinos.
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False. -It would would require lead more than a light-year thick to stop any average neutrino. -Neutrinos pass through our body everyday but do not cause any damage
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By observing solar neutrinos, we can learn about nuclear fusion deep in the Sun's core.
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-True. -Some of the electron neutrinos produced by fusion change into neutrinos of the other two types during their trip from the suns core to its surface -which has helped prove that our understanding of fusion in the Sun
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three types of neutrinos
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tau, electron, muon
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Describe two ways in which the thermal radiation spectrum of an 8000K star would differ from that of a 4000K star.
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-An 8,000K star would emit a lot more light at every wavelength than the 4,000K, making it bluer -Hotter star emits photons with a higher average KE
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Doppler effect
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-the change in frequency in light due to the source's motion from the observer -Object moving towards us > shorter wavelength > blueshifted -Object moving away > longer wavelength > redshifted -For rotating objects, we see part of the object coming toward us and part of it moving away from us. -If we can't see the different parts of the object clearly, we will see blueshifted, redshifted, and unshifted light all at once, which makes the lines look broader
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In hydrogen, the transition from level 2 to level 1 has a rest wavelength of 121.6 nm. Suppose the wavelength of star A is 120.5 nm, 121.2 nm in Star B, 121.9 nm in Star C, and 122.9 nm in Star D. Which stars are coming towards us? Which are moving away? Which star is moving fastest relative to us? Explain your answers without doing any calculations.
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-If the observed wavelength is less than the rest wavelength, then the star is moving towards us (blue). -If the observed wavelength is more than the rest wavelength, then the star is moving away from us (red). -The greater the difference between the rest wavelength and observed wavelength, the faster the star is moving.
