ANALYSIS: The Higgs Boson Should Have Crushed the Universe
"You know it's a crisis when you start seriously talking about decaying dark matter," study co-author Neal Katz at the University of Massachusetts at Amherst said in a statement.
There still may be a simpler explanation for this missing light, however. Astronomers could be underestimating the fraction of ultraviolet light that escapes from galaxies in the nearby universe. "All that one needs is an average escape probability on the order of 15 percent to relieve the discrepancy," Loeb told Space.com.
Nearby, recent "low-redshift" galaxies have less gas to absorb ultraviolet rays that more distant, early "high-redshift" galaxies, Loeb noted.
"The more I think about it, the more plausible it appears that the escape fraction of ultraviolet photons is higher in local galaxies than in high-redshift galaxies," Loeb said.
On the other hand, "the biggest problem with this possible solution is that there are measurements of local galaxies that indicate the average escape fraction is significantly lower than 15 percent - more like 5 percent," Kollmeier said."In principle, it is possible that these galaxies are not representative and therefore we need to do more such measurements, but we cannot just dismiss the data."