Do we have an estimate of how much noise, if any, say caused by cosmic rays in particular, is present in the CMB datasets and the maps based upon them? Can we extrapolate a figure from the cosmic ray flux estimated to enter our atmosphere?

My knowledge on this subject is limited so my apologies if I have made a wrong assumption regarding the interaction, if any, between these two sources of radiation.

  • 3
    $\begingroup$ What do you mean by "how much noise"? The CMB has some fluctuations in it, but why do you think of "cosmic rays" as the cause? "Cosmic rays" are highly energetic events, they are usually rather gamma rays than microwave radiation. $\endgroup$
    – ACuriousMind
    Commented May 29, 2016 at 11:26
  • 2
    $\begingroup$ it is only the "cosmic" they have in common. $\endgroup$
    – anna v
    Commented May 29, 2016 at 14:39
  • $\begingroup$ @annav thanks for your comment. I do appreciate this "cosmic" distinction, my apologies for not being clear in my question, I choose cosmic rays because of their energy levels and subsequent possible large contribution to noise, but the answer clears up the main contributions for me. Regards $\endgroup$
    – user108787
    Commented May 29, 2016 at 16:58

1 Answer 1


Cosmic Rays are most often high-energy particles, mostly protons and alpha particles accelerated to high velocities by cosmic magnetic fields. They do not show up in the microwave wavelength range that comprise the CMB.

As @ACuriousMind says in the comment, there is contamination in the CMB, but this is mainly due to Galactic dust and Bremsstrahlung from electrons in the Galactic magnetic field. This is also the reason why a broad band around the galactic plane has been masked out of the data used to calculate the anisotropies in the CMB.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.