A secret population of hidden galaxies suffusing the universe in a soft glow of far-infrared light have been strongly suggested to exist, based on careful detective work into some of the most unique data to come from Europe's Herschel Space Observatory.
The galaxies, if they are real, are not necessarily a surprise. The cosmos is filled with light across all wavelengths — it's just that the far-infrared component seems to be stronger than can be accounted for by all the galaxies we can see in visible light. In other words, there must be something else in the universe producing its glow.
