science

There is a diffuse gamma glow around the center. There are only a couple of paragraphs quoting the most silly versions of explanations: Dark Matter interaction and spinning neutron stars.

The article offers no answers.

IMO, it's FAR more likely we just don't entirely know how dense the region is and what atoms/particles are in it, and it could be as silly as interstellar particles getting excited from high energy particles that escape the SMBH accretion disc. Or some similarly 'common' thing.