A balloon borne instrument called ARCADE-2 is causing some excitement as it seems to have discovered an excess of extragalactic emission at frequencies around 3.3 GHz. The above link points to a New York Times article on the result, which shows the prominence it’s achieved. The relevant papers can be found here on the arXiv, including the basic result here and discussion of the excess here.
The three most likely sources for error in these observations are stated as being galactic emission, systematic effects and unaccounted for radio emission from faint known sources. The authors conclude that the signal they see is grater than these possible contributions and suggest radio emission from the first generation of weak active galactic nuclei at high redshift.
I’m not sure what to make of this just yet. Claims like this from single experiments need to be checked and independently confirmed before we can give them serious weight, but it is an interesting result. The most interesting thing is that the waveband where the signal is detected, 3GHz, can be observed from the ground, so the next generation of sensitive radio telescopes, like eMERLIN and EVLA, should be able to make rapid progress on the problem once they start to operate.