Dark matter 'halos' - the huge, invisible cocoons of mass that envelop entire galaxies and account for most of the matter in the universe - aren't completely dark after all but may contain a small number of stars, a new study by University of California, Los Angeles and the University of California, Irvine found.
Scientists have long disagreed about why they see more light in the universe than it seems they should - that is, why the infrared light they observe exceeds the amount of light emitted from known galaxies.
When looking at the cosmos, astronomers have seen what are neither stars nor galaxies nor a uniform dark sky but mysterious, sandpaper-like smatterings of light, which Edward L (Ned) Wright from UCLA refers to as "fluctuations".
The debate has centered around what exactly the source of those fluctuations is.
One explanation is that the fluctuations in the background are from very distant unknown galaxies. A second is that they're from unknown galaxies that are not so far away, faint galaxies whose light has been travelling to us for only 4 billion or 5 billion years (a rather short time in astronomy terms).
Researchers present evidence that both these explanations are wrong, and propose an alternative.
The first explanation