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SYFY WIRE Gamma Rays

Could destroyed dark matter have created an orb of gamma rays at the center of our galaxy?

By Elizabeth Rayne

There is a mysterious glowing orb of something in the center of the galaxy — but don’t go tweeting #aliens just yet.

Even though alien beings would have a better chance of survival near the galactic center, if any actually exist over there, they wouldn’t want to be near this phenomenon. It was first discovered by NASA’s Fermi Gamma-Ray Telescope in 2009 and is known as the Galactic Center Excess. Scientists are now suggesting the otherworldly glow is being caused by dark matter particles smashing into and annihilating each other, creating gamma rays (which are the last thing any form of life wants to be remotely near).

Analyzing Fermi data, along with the results of an ISS experiment and gamma ray observations from dwarf galaxies that are not too far away, led researcher Mattia Di Mauro to believe that this light probably has a dark origin. This has never been hypothesized before. He was also able to figure out the shape of this gamma ray glow and how its is positioned in space, along with how much energy it emits, and published those findings in Physical Review D.

“This excess of gamma rays cannot be explained with the known processes and components,” Di Mauro, who more recently coauthored a second study with colleague Martin Wolfgang Winkler, told SYFY WIRE. “A signal of dark matter particles annihilating in the center of the Galaxy is compatible with all the characteristics of the excess, including the flux, spatial distribution, and position."

Di Mauro found the glow to be spherical and symmetrically centered right in the middle of our galaxy. He then wanted to see what kind of proverbial light the actual radiation from the gamma rays could shine on what heavy dark matter particles have to do with the excess.

dwarf galaxy

Comparing the Galactic Center Excess to dwarf galaxies revealed that the signals were similar. They could be seen from data that suggests dark matter annihilation, which supposedly happens when particles of dark matter take each other out and are reduced to subatomic particles and the antimatter mirror-images of those subatomic particles.

Gamma rays are the most energetic waves in the electromagnetic spectrum, with wavelengths too short to be visible to the human eye. They are so energetic because they are released by objects with the most energy in the cosmos, including supernovas, neutron stars, pulsars and regions surrounding black holes. Sagittarius A* is the black hole in our galactic core that may or may not be a reason for the excess gamma ray emissions. The center of the galaxy is also swarming with stars. Because neutron stars are the cores of monster stars that emerge after those stars go supernova, immense amounts of gamma rays could have come from the supernovas that formed them.

“The analyses for [the] latest particles are compatible with the dark matter model of the Galactic Center Excess,” Di Mauro said. “The signal, in particular the flux as a function of energy, has a very specific shape and characteristics. By studying these properties together with other data from subatomic particles and dwarf galaxies, it is possible to narrow down the cross-section of dark matter mass and annihilation.”

Neutron stars themselves emit hardcore gamma rays. So do pulsars, which are neutron stars that rotate so fast that one would appear as a super-bright blur. There are thought to be about a billion neutron stars in the Milky Way, and 2,000 of those are probably pulsars. The problem with pulsars is that even our most advanced technology cannot see them because the beams they give off are so narrow. It is possible that many had gone unaccounted for in the Fermi observations.

Dark matter particles can still be investigated right here on Earth. They sometimes come out of proton-on-proton collisions in huge particle accelerators like the Large Hadron Collider. Though rare, they can be observed.

Some scientists are still skeptical about Di Mauro’s results, insisting that pulsars, possibly all those undetected pulsars, are behind the excess. He acknowledges this could be the answer, but believes that the real culprit can only be found through more research.

“I am working on more directly testing the pulsar hypothesis to see if this is indeed a viable interpretation,” he said. “The center of the galaxy and dark matter searches is certainly a very active and exciting topic of research and I am sure that it will provide us interesting results in the future.”