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Is there something that Sun actually absorbs?

  1. Sep 29, 2009 #1
    So is there? :) ... Is there anything (radiation waves, particles, what not...) That Sun absorbs more than it emits? I guess it absorbs visible light of stars behind it, but it emits a ton of more. But is that the case with all EM frequencies? What about gamma rays or any other background radiation? How about small particles, like neutrinos? Something that would actually render a black circle in Suns place on image map when detecting?
  2. jcsd
  3. Sep 29, 2009 #2


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    Gamma rays, cosmic rays (high energy protons) would be among the things you are asking about. The sun emits lots of neutrinos, I believe much more than absorbed.
  4. Sep 29, 2009 #3


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    1] Is there some reason that they are not just sunspots?

    2] Something you must first realize when analyzing a picture of the sun is that it is processed. Never mind that it is colour-filtered. Among many other things, the exposue is turned down by zillions of stops. This means that ultra-ultra-bright areas are seen as white, whereas merely ultra-bright areas are seen as dark.

    i.e. if one billion watts is represented as white, then a "mere" 100 million watts will look black.
  5. Sep 30, 2009 #4
    Thanks to both of you.
    So in fact there is more high energy protons comming from everywhere else than from the direction of sun?
    1] I am not going after sunspots as in spots on the sun..i think! :)
    2] I do understand that I think. My question would be about higher energy levels (in some particular form or frequency) comming from background space rather than our own emmiting sun. I dont have an issue with Earth or other planets and moon, i think they definetly show less of 'energies' comming from them.
  6. Sep 30, 2009 #5


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    The sun is a lightweight in the cosmic ring. Relatively small and quiet.

    There are some monstrous heavyweights out there putting out very hard radiation.

    Or are you suggesting that the sun is blocking/absorbing this hard radiation? OK, I can see that. It is a million kilometres thick and 10 times denser than lead at its core.
  7. Sep 30, 2009 #6


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    A thought experiment . . . is the flux density of cosmic rays lesser in the direction of the sun? If so, it suggests the sun occludes them.
  8. Oct 1, 2009 #7
    I would think so also. As shiny and radiating our Sun is, it is still a great amount of mass that really shield us from every imaginable radiation comming from deep space, from that direction that is.

    I would just like to know what kind of radiation it might be. Is there any radiation like that identified? What about those from "monstrous heavyweights"? Can we detect them from everywhere but not from the direction of sun? Can we map those on celestial sphere? Has it been done?
  9. Oct 1, 2009 #8


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    This doesn't make a whole lot of sense to me. Obviously, the sun will block any radiation from sources directly behind it. A "map" of this would just be a map of the sun's path through the sky. Why this matters, I don't know - it would seem to be the opposite of what astronomers typically look for.
  10. Oct 1, 2009 #9


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    As a practicable matter, can you devise an experiment that might test this? It's not so hard...
  11. Oct 1, 2009 #10


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    The OP is asking whether the Sun is a net absorber of any particles. If it is, the Sun would appear black when a photo is taken using those particles instead of photons. The OP wasn't talking about sunspots or suggesting that the Sun blocks cosmic rays.
  12. Oct 2, 2009 #11


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    I did not suggest otherwise.
  13. Oct 2, 2009 #12


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    Quibble: a "shield" that covers a bit over half a degree of angular size is not shielding "us" from much!

    For the Sun to appear black, you'd have to be observing a background of some kind, or using a very long exposure. I'd be surprised to see an image where this occurs. There is, of course, the deliberate use of shields in some image specifically to block out the Sun. See, for example, this Astronomy Picture of the Day for October 29 2003, of a solar flare. (The image is a link to the APOD website)

    More relevant for shielding the Earth are the Sun's magnetic fields, which divert charged particles like cosmic rays. From High Energy Cosmic Rays and the Sun at SLAC, Stanford:

    The sun does, however, also have an effect on high-energy cosmic rays. High-energy cosmic rays come from interstellar space and are sometimes called Galactic Cosmic Rays (GCRs), even though it is thought that some of them come from beyond our galaxy. The solar wind mentioned above consists of a continuous stream of plasma, loose protons and electrons. The region of space in which the influence of the solar wind is felt, called the heliosphere, extends far beyond the orbit of Pluto. Because the solar wind is a plasma, it is electrically conducting and transmits a part of the sun's magnetic field. When GCRs approach the sun they encounter the heliosphere and the magnetic field within it. Because of the shape of the magnetic field, the GCRs lose some of their energy, and the lower-energy ones never reach the vicinity of the earth. In times of high solar activity (high levels of solar wind) this effect is stronger and fewer GCRs reach the earth.

    This is not a case of the Sun itself being the shield, however, and would not make the Sun appear as a black disk in an image.

    Cheers -- sylas
  14. Oct 3, 2009 #13
    Thanks all for ther input. I liked "opposite of what astronomers typically look for" part, it's usualy worth to look the opossite way (ask Rutherford :). I feel there might be something to learn from Sun's absorbing powers, while ignoring it's emission, rather than always making sure that Sun is not in the way of our background radiation measurements.

    How about extremely *low* frequency EMs? They are suppose to go through everything. Do they go through Sun? Or does Sun emits them even more?
  15. Oct 3, 2009 #14


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    If you wanted to see if the Sun blocks some background emissions, you might try to measure them away from the Sun, and then see if they are attenuated by the Sun. Of course the problem with this method is that no matter how sensitive and accurate we can make our sensors, the radiational output of our home-star will swamp them when we try to measure emissions in the direction of the Sun.

    Question: Is there a particle that might be slowed or absorbed by the Sun so that (even if the Sun emits these particles, too) we might see a relative deficit of them when looking at the Sun? How about really energetic particles that interact only slightly with condensed matter?
  16. Oct 3, 2009 #15
    I wish I had energy/wavelength line chart measurements with values plotted for directions from: couple of random 'black' point in space, Sun, Moon, Earth (downwards), and couple of stars. Wavelengths to go from electron size to star size. Is that a lot to ask? ;-)
    Anyway, I would really be interested in any parts of chart where random black points do not have lowest values. Even if there werent any such parts, it would still answer my question. At least for EM fields. We can discuss any other particles after we rule out EMs.
  17. Oct 3, 2009 #16

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  18. Oct 3, 2009 #17
    Thanks Vanadium, I'll need some time to chew on it. Did find this on Wikipedia on muons, same detector: http://en.wikipedia.org/wiki/File:Moons_shodow_in_muons.gif . No sun there though. Any muons coming from "below" the Earth you think? I should think yes, since they go through Sun. Or they are all absorbed but shadow is contaminated with reflections and muons from other directions? I am way over my head anyway I think. Thanks for directions I have a lot to read.
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