By Andrew Grant
The search for a suspected calling card of the universe’s most elusive matter has come up empty.
Multiple days of telescope time spent looking for a specific X-ray glow coming out of the nearby dwarf galaxy Draco failed to turn up any signal, two University of California, Santa Cruz astrophysicists report online December 7 at arXiv.org. Finding such a glow would have offered a compelling clue for the identity of dark matter, the invisible, inert stuff that makes up more than 80 percent of the universe’s matter. The study’s authors say that the absence of the X-rays in Draco, one of the most dark matter–dominated objects known, means that scientists had previously detected the X-ray emissions of interstellar atoms rather than dark matter.