In 2009, Dan Hooper and his colleagues found a glow coming from the center of our galaxy that no one had ever noticed before. After analyzing publicly available data from the Fermi Gamma Ray Space Telescope, a satellite launched a year earlier, the team concluded that the center of the Milky Way was radiating more gamma rays than astrophysicists could account for.

The finding was so unexpected that, at the time, few believed that it was real. It didn’t help that Hooper wasn’t a member of the Fermi collaboration, but rather an outsider picking over the data that the Fermi team made public. One of the scientists working on Fermi called his work “amateurish,” arguing that Hooper simply didn’t know how to properly interpret the data.

Yet as time wore on, astrophysicists began to realize that there’s a lot more high-energy radiation streaming through the galaxy than they could explain. Just a year before Hooper started analyzing Fermi data, a gamma-ray detector in New Mexico called Milagro had found an abundance of super-energetic gamma rays that appeared to come from all across the galactic plane. And in 2014, the Alpha Magnetic Spectrometer (AMS), an experiment on the International Space Station, found more antimatter streaming through the galaxy than could be accounted for, confirming earlier observations by satellite and balloon experiments.

These three anomalies — if real — showed that something was going on in the universe that we didn’t know about. A number of astrophysicists, including Hooper, began to argue that two of these mysterious signals were an astrophysical echo of dark matter, the profoundly mysterious substance thought to make up about a quarter of the universe.

This year, almost a decade after the launch of the Fermi telescope, researchers have nearly arrived at a consensus. First, pretty much all astrophysicists now agree that the center of our Milky Way produces much more gamma radiation than our models of known gamma-ray sources suggest, said Luigi Tibaldo, an astrophysicist at Stanford University and member of the Fermi collaboration, thus validating Hooper’s once-“amateurish” claims.

Second, all that extra radiation is probably not due to dark matter. A number of recent studies have convinced many researchers that pulsars — rapidly spinning neutron stars — can explain all three mysteries.

The only problem is that no one seems to be able to find them.

Dark Matter Days

The center of the galaxy is a crowded place, dense with stars, dust and — presumably — dark matter. Astrophysicists have long believed that dark matter is probably made out of particles that don’t readily interact with ordinary matter — so-called “weakly interacting massive particles,” or WIMPs. Occasionally these WIMPs might collide with one another. When they do, they could produce gamma rays. Perhaps that’s just what’s going on in the galactic center, Hooper suggested back in 2009.

The theory dovetailed with another idea that Hooper had put forward just a year earlier. In 2008, he and three co-authors published a paper arguing that collisions of neutralinos — a type of WIMP — generated showers of exotic particles that then decayed into elementary particles. The process would explain the anomalously high levels of positrons (the antimatter counterpart of electrons) found earlier by a space-based experiment called Pamela.

In this case, Hooper was in good company. Since Pamela’s first results, “without exaggeration” around 1,000 papers have tried to explain the positron excess mystery, said Tim Linden, an astrophysicist at Ohio State University. The majority of these papers favored the dark-matter interpretation. In 2014, the Pamela results were buttressed by data coming from the AMS.