Sun is generating energy by nuclear fusion. And nuclear fusion will emit energy in the form of gamma rays.

Normally earth's ozone filtering the Ultraviolet radiation. And magnetic fields of earth deflecting the cosmic rays(charged particles).

But what kind of natural system protecting us from sun's gamma ray as it is main product of nuclear fusion?

Note: As we know gamma ray can be blocked by denser materials like several meters of thick lead (Pb).

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    $\begingroup$ Note that if none of the high-energy radiation generated at the sun's core got reabsorbed and had its energy converted into heat, then the sun wouldn't be hot. (In fact, the neutrinos do escape, and don't contribute to heating.) $\endgroup$ – user4552 Oct 18 '14 at 18:01
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    $\begingroup$ Minor correction to your logic: Many high-energy photons (in the regime where their interaction with matter is dominated by Compton scattering off electrons) basically only care about the column density along their path. And the full atmosphere has the same column density as 1 meter of lead (or 10 meters of water). That is, we only like dense materials because they make shielding more compact. $\endgroup$ – user10851 Oct 18 '14 at 18:08
  • $\begingroup$ @ChrisWhite Thanks for the info. This is the first time I heard about that. $\endgroup$ – sugunan Oct 18 '14 at 18:11

That's a good question and I think the answer may surprise you. It turns out that indeed, there's a lot of gamma ray radiation being produced in the sun's core from fusion reactions, so why are we not bombarded by gamma ray radiation? Those gamma ray photons need to escape from the sun's core, into the outer edge, and then finally from the surface. These photons are colliding with matter constantly, resulting in a photon diffusion process. It actually takes the average gamma ray photon about 170,000 years to diffuse out of the radiative zone. Once a gamma ray actually diffuses outward to the surface as a result of the constant collisions it has been converted into millions of visible wavelength photons.

more here: Solar Core Wiki

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    $\begingroup$ For a moment I was expecting "Solar Core Wiki" to link to solarcore.wikia.com (or similar) and was surprised that was a thing (it's not). $\endgroup$ – user253751 Oct 19 '14 at 0:33
  • $\begingroup$ @ Elvex: Thanks for the clear explanation. The same explanation given in this video also. youtube.com/watch?v=sNXelB6gIzQ $\endgroup$ – sugunan Oct 19 '14 at 4:56

As you can read on wikipedia

Sun produces Gamma rays as a result of the nuclear fusion process, these super-high-energy photons are converted to lower-energy photons before they reach the Sun's surface and are emitted out into space. As a result, the Sun does not emit gamma rays. The Sun does, however, emit X-rays, ultraviolet, visible light, infrared, and even radio waves not to mention neutrinos.

Gamma ray photons produced by fission make their arduous journey to the surface of the Sun, they are continuously absorbed by the solar plasma and re-emitted to lower frequencies. By the time they get to the surface, their frequencies are mostly only within the IR/visible light/UV spectrum.


Actually, we don't need a lot of protection from solar gamma rays because they never reach us. Here's Wikipedia's take on the matter:

Although the Sun produces Gamma rays as a result of the nuclear fusion process, these super-high-energy photons are converted to lower-energy photons before they reach the Sun's surface and are emitted out into space. As a result, the Sun does not emit gamma rays.

So while lots of gamma rays can be formed during nuclear fusion, not many escape the Sun. We do have to worry about ultraviolet rays, but the ozone layer gives us a lot of help with that.

Note: NASA has a page that briefly discusses the Sun and gamma rays. There is an inaccuracy or two regarding Earth's magnetic field's ability to stop gamma rays (it can not), but it should prove helpful.

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    $\begingroup$ That's an error in the NASA page. Magnetic fields have no effect on gamma rays, only on charged particles. $\endgroup$ – user4552 Oct 18 '14 at 17:58
  • $\begingroup$ @BenCrowell Ahh, I should have realized that. $\endgroup$ – HDE 226868 Oct 18 '14 at 17:59
  • $\begingroup$ I think what NASA was trying to say (not too clearly) is that charged cosmic rays (not gamma rays of course) hit the upper atmosphere all the time, and this then produces gamma rays, so you want to point your gamma ray telescope away from Earth to avoid contamination. $\endgroup$ – user10851 Oct 18 '14 at 18:00
  • $\begingroup$ @ChrisWhite I think I'm just going to get rid of that section. $\endgroup$ – HDE 226868 Oct 18 '14 at 18:00
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    $\begingroup$ @HDE226868 actually that page has a good image, since the Sun does produce some gamma rays. Its corona is millions of kelvin, so there is a (small) source other than the core. $\endgroup$ – user10851 Oct 18 '14 at 18:01

The Earth's atmosphere stops most Gamma Rays. It is "as thick to gamma-rays as a twelve-foot thick plate of aluminum".

The Gamma Rays that make it to our atmosphere and impact another particle are absorbed. Secondary particles are produced in this interaction, and these particles can be more penetrating and damaging.

Source: Gamma Rays and Our Atmosphere - Nasa.gov subdomain

  • $\begingroup$ if atmosphere is 12 feet thick aluminum equivalent. Is the space ships are build with 12 feet thick aluminum? And is space suit capable of stop heavy gamma ray radiation? I hope "Elvex's" answer is most suitable. $\endgroup$ – sugunan Oct 19 '14 at 4:37
  • $\begingroup$ @sugunan Space suits are not capable of stopping gamma rays. Nothing can stop gamma rays except by being very thick. $\endgroup$ – user10851 Oct 19 '14 at 5:41
  • $\begingroup$ So the gamma ray not even leaving the sun's surface. $\endgroup$ – sugunan Oct 19 '14 at 7:14

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