Galactic Center GeV Excess

The Galactic Center GeV Excess (GCE) is an unexpected surplus of gamma-ray radiation in the center of the Milky Way galaxy that is unexplained by direct observation.[1] As of 2020, this excessive (and diffused) gamma-ray radiation is not well understood by astronomers.[2][3][4][5] However, astronomers have suggested that self-annihilating dark matter may be a dominant contributor to the GCE, based on analysis using non-Poissonian template fitting (NPTF) statistical methods,[3] wavelet methods,[5] and studies by other astronomers may support this idea.[6][7] More recently, in August 2020, other astronomers have reported that self-annihilating dark matter may not be the explanation for the GCE after all.[8][9] Other hypotheses include ties to an unseen population of millisecond pulsars[10] or young pulsars, burst events, the stellar population of the galactic bulge,[11] or the Milky Way's central supermassive black hole.[12]

Gamma-ray radiation (greater than 1 Gev) detected over the entire sky; brighter areas are more radiation (five year study by Fermi: 2009–2013)

Two percent of the gamma ray radiation in a 30° radius circle around the galactic center is attributed to the GCE. While some controversially argue that it might be radiation from dark matter (which is not otherwise known to radiate) or another exotic explanation, some still believe that conventional objects such as pulsars could explain the GCE.[1]