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4

Yes, the sun's mass isn't constant causing disturbances of orbits, but should you care. Mass of sun now: $\approx 2 * 10^{30}$ kg so $E \approx 1.8 *10^{47}$ J. Radiation per year is about $10^{34}$ J. You've got a lot bigger problems that affect your calculation of orbits. Especially like where Jupiter is relative to where you thought it was. Namely the ...


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As has been commented by fractalspawn this is almost certainly a photochromic effect (https://en.wikipedia.org/wiki/Photochromism). In this process a molecule in form A can absorb a visible or UV photon and be isomerized into another form B. This will have a different absorption spectrum than the starting material and if this absorbs in the visible part of ...


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A suggestion would be to include straight standing lines that represent buildings. And also include the angle of the rays of the sun with respect to the horizontal ground at a specific time. And compare using the known angle from the ground, whether it is really the converging rays, or parallel rays that will produce such projections: The angle can be ...


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It's just a case of a perspective. I've just modeled it in blender to see how it should look like making sure that the beams are perpendicular. That's what i get.My model is not perfect but you see what's going on.


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To get a full account of this buy the Dover edition of the book by van de Hulst "Light Scattering by Small Particles." This involves Mie scattering, which is more general than Rayleigh scattering at the red or IR regime. The scattering has intensity lobes, similar to antenna lobes in electromagnetic applications, and what these crepuscular rays are the ...


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As I mentioned in first comment underneath original question, the Hertzsprung-Russell diagram is probably the single best measure of "average" if you have to choose just one measure. But since there seem to be many more additional answers and comments than I'd assumed would be posted, let me add the following remarks that seem to have been overlooked. In ...


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Based on my own anecdotal evidence, it doesn't. Several years ago there was a partial solar eclipse in my area. I don't remember precisely how much of the sun's disk was covered - it wasn't much, surely nowhere near 90% - but I do remember getting out of the house in the morning, thinking "hmm, it's quite dark today", then having the eerie realization that ...


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The shape of the Sun tells you something about it's mean rotation rate. The faster it spins, the more oblate it gets. See Why is the Sun almost perfectly spherical? Of course you are not sensitive to the nuances of latitudinal or radial differential rotation. For the former you really do need to "see" the surface, for the latter you need helioseismology ...


7

The Sun is decidedly NOT an average star, except it is on the hydrogen-burning main sequence, where $\sim 90$% of stars in the local stellar population are found. A much better appreciation of the Sun's "averageness" is gained from looking at a Hertzsprung-Russell diagram (luminosity vs effective temperature or equivalently, absolute magnitude versus colour)...


0

This actually contains two questions. 1) The sun seems brighter (more dazzling) if there is more scattering in the atmosphere. The sun would actually look very small to us in the sky if there were no atmosphere (it's the same angular size as the moon) and most of the brightness seen in the direction of the sun is from small deflection rayleigh scattering. ...


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Human perception is generally logarithmic. For example, the perceived loudness of a sound is measured using decibels, where an decrease of $10 \text{ dB}$ divides the sound intensity by $10$. So if the eclipse were heard instead of seen, "90% coverage" might mean reducing the intensity from $120 \text{ dB}$ to $110 \text{ dB}$, a small change. Perceived ...


42

The graph looks exponential because the vertical axis is logarithmic! If you were to re-plot it as linear lumens per square meter, it would be much more v-like, or even u-like. It so happens that a logarithmic plot matches our subjective perception of light intensity better than a linear one would. That's a result of our eyes having evolved to work well in ...


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As a followup to @honeste_vivere's note about the H-R diagram, our sun really is living in the middle of average-town: The image, from Wikipedia plots 22,000 stars. When you plot a star's temperature vs brightness, they seem to follow certain patterns. Our star lies right in the middle of the boring main sequence.


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From the wiki article on the sun's radiation: Solar irradiance spectrum above atmosphere and at surface. Extreme UV and X-rays are produced (at left of wavelength range shown) but comprise very small amounts of the Sun's total output power. You ask: My Question is, why exactly does the intensity vanish below 240 nm ? If i look at the plank's law, ...


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Why is the Sun called an “average star”? The sun is a yellow dwarf star and dwarf stars are the most common in the universe. Technically, the sun's spectrum peaks in the range of green light, but we see it as effectively white. I am inclined to think if an astronomer or physicist told you the sun was "average" it is because it is part of the main ...


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Describing the sun as an average star is probably more of a reaction against the idea that there is something unique about it. Obviously there is for us, since it is the star that we happen to be in orbit around, and much closer to than any other star, and hence historically the sun has been considered rather unique. But over the centuries we've discovered ...


1

What are the properties of proton+proton fusion reaction $$p + p → 2H + e^+ + ν_e + 0.42 MeV$$ making it hard to replicate on Earth? This reaction has been replicated many times on Earth. The problem is that the reaction requires a proton to decay into a positron and a neutron at the instant the collision occurs. This is extremely unlikely. This is why, ...


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The problem is that there is a huge potential barrier for the fusion of two protons due to their electrostatic repulsion, and this makes fusion an extremely low probability process. Even in the extreme conditions in the core of the Sun proton fusion is exceedingly slow - this is discussed in Why does the Sun's (or other stars') nuclear reaction not ...


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The reaction has been studied in accelerators A bubble chamber study of proton-proton interactions at 4 GeV/c Part I—Elastic scattering, single-pion and deuteron production .Summary Elastic scattering, single-pion and deuteron production have been investigated. The cross-section for elastic scattering is σelastic = (13.5±0.3) mb. The angular ...



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