The Daily Galaxy
The vast reaches of empty space between galaxies are bridged by tendrils of hydrogen and helium, which can be used as a precise “light meter.” In a recent study published in The Astrophysical Journal Letters, a team of scientists finds that the light from known populations of galaxies and quasars is not nearly enough to explain observations of intergalactic hydrogen. The difference is a stunning 400 percent.
“The most exciting possibility is that the missing photons are coming from some exotic new source, not galaxies or quasars at all,” said Neal Katz a co-author from the University of Massachusetts at Amherst. For example, the mysterious dark matter, which holds galaxies together but has never been seen directly, could itself decay and ultimately be responsible for this extra light.