One of the biggest pieces of evidence for the Big Bang Theory is the cosmic microwave background information, because, according to the theory, this radiation is left over from the Big Bang itself. It is not the only background radiation we detect though as infrared observations have revealed their own background. Exactly where this radiation is coming from is now in question as new observations with the Spitzer Space Telescope by researchers lead by the University of California at Irvine challenge the current theories.
Traditionally, researchers have believed this radiation is actually coming from distant galaxies that are two faint to observe directly, but the collective radiation from them is observable. The Spitzer observations however are too bright to support the distant-galaxy theory. Instead what the researchers are suggesting is that the radiation is coming from stars located between galaxies and galactic clusters. Galactic collisions, like car crashes, can be quite violent and throw debris away from the crash site. For galaxies this debris can include stars which will keep burning despite being ejected from their home. These stars would still be too faint on their own to observe directly, but together, like the distant galaxies, could generate the background radiation we see.
While this is an intriguing theory and does have this experiment's support, it will be some time before more evidence can be found for it or the theories it would replace. The James Webb Space Telescope is the next generation space observatory still being developed and constructed, and it will have the power to spot these previously invisible objects that are lighting up our sky.