# Tag Info

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The Sun rotates, taking about 24.5 days to complete a revolution at the equator, a bit longer at the poles. This makes the Sun have a bit of an equatorial bulge, which in turn means that the Sun's gravity field is not quite uniform. The Sun's J2 is very small and the effect is well known. Very large stars are asymmetric due to being close to the Eddington ...

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I think the definitive work is that of Hoyle & Fowler (1960). They argued that supernovae were produced by two possible mechanisms - what they called an implosion/explosion or an explosion within degenerate matter. Both of these mechanisms required very high internal temperatures ($>2\times 10^{9}$ K) and they argued that this could only be achieved ...

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It would be my understanding that the work by Hoyle in the late 40s to early 60s established a mechanism by which massive stars could supernova, and so explain the "Type II" supernova that had been observed. It would have been apparent from the start that the sun was no a "massive star". So since the late 40s/early 50s, it has been known ...

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You may want to look into the Chandrasekhar limit. Dr. Chandrasekhar did his original work on this back in the early 1930's but received the Nobel Price in Physics in 1983. On Stars, Their Evolution and Their Stability

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The earth is smoothly and constantly moving around the sun. At the moment of the equinox, a line from the center of the sun to the center of the earth passes through the equator. That only lasts an instant. Before that instant, the line is on one side of the tilted equator, and after that, it's on the other side. The day labeled "the equinox" is ...

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Disclaimer I have no medical knowledge and do NOT recommend following what I describe below. Any children that read this should not copy it. I was stupid and it was pointless. Especially do NOT look at the sun with a telescope. It will burn the back of your eyes and cause blindness. When I was about 11, I was told not to look at the sun but not told why. ...

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This webpage gives a lot of background information. Key points: It does seem to be the overall dimness of near-total eclipses that allows the pupil to widen enough to allow damaging levels of UV in. There are cases of eye damage from staring at the full sun, and also cases of staring at the noonday sun without apparent damage (not recommended). Perhaps ...

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Glancing at a partial solar eclipse is about as dangerous as glancing at the Sun on any other day. If you look at the Sun a few minutes after sunrise or a few minutes before sunset, when the Sun's altitude is low, the light is filtered through a lot of air, and most of the ultraviolet is scattered, so it's a lot less dangerous than looking at the Sun in the ...

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Imagine you are watching a car drive down the street from right to left (in front of a building. It goes from right to left. Now imagine watching that car with your head on your left shoulder. The car goes from the bottom of your point of view to the top. If you move your head as the car is driving past, you will see it come from the right but leave to the ...

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There are problems with the scenario outlined above. Firstly, if the CNO cycle were to operate, it would have to operate for millions/billions of years to noticeably affect the relative abundances of CNO in the solar photsophere. That is because the core is embedded within a radiative zone where only comparatively slow mixing processes operate. A much more ...

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The answer to whether a normal star can contain a core of degenerate neutrons is a yes. Thorne & Zytkow 1977 produced numerically models where a neutron star becomes embedded in the center of a massive giant or supergiant star, surrounded by a large gaseous envelope. In this scenario, the main source of energy becomes not nuclear fusion but instead ...

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https://en.wikipedia.org/wiki/Hot_Jupiter For a much hotter Jupiters, a mass loss is estimated as 5-7% over the star lifetime. Our rather cold one (even with Sun as a red giant), being exposed to the heat much less time, will lose probably way less. Capturing a significant amount of the Sun ejected matter will probably not happen. The matter is too hot and ...

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Assumptions Let's assume your friend and yourself are at the exact same coordinates but at different altitudes (e.g. right at the edge of a cliff or in the same building but on different floors). Both latitude and longitude influence the time of sunset, so if you and your friend are at different locations, you don't have enough information to answer the ...

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The page you refer to is about sunrise/sunset throughout the year, but what you really care about is differences in the geometry on one day. This is sometimes expressed as different observers seeing the horizon at different distances, or sometimes as an angle, a “dip” of the horizon when seen from higher altitude. Thinking about that geometry should get you ...

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I don't think this particularly useful way to think about it. The equator is the equator, Cancer is 23.4 North, and Capricorn is 23.4 South. The equator is a great circle on the sphere of the sky, but the Tropic of Cancer is not a great circle. These are fixed. Now (in Northern Hemisphere summer) the sun is directly above a point on (or near) the tropic ...

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