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. This spherical source of radiation was first detected in 2009^[1][2] by the Fermi Gamma-ray Space Telescope and is unexplained by direct observation.^[3] Two percent of the gamma ray radiation in a 30° radius circle around the Galactic Center is attributed to the GCE. As of 2020^[update], this excessive (and diffused) gamma-ray radiation is not well understood by astronomers.^[4][5][6][7]

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

Some astronomers argue that self-annihilating dark matter (which is not otherwise known to radiate) may be the cause of the GCE, while others prefer a population of pulsars (which have not been observed) as the source.^[8][3]

Astronomers have suggested that self-annihilating dark matter may be a dominant contributor to the GCE, based on analysis using non-Poissonian template fitting statistical methods,^[5] wavelet methods,^[7] and studies by other astronomers may support this idea.^[9][10] More recently, in August 2020, other astronomers have reported that self-annihilating dark matter may not be the explanation for the GCE after all.^[11][12] Other hypotheses include ties to a yet unseen population of millisecond pulsars^[13][14] or young pulsars, burst events, the stellar population of the galactic bulge,^[15] or the Milky Way's central supermassive black hole.^[16]

See also

• Galactic Center – Rotational center of the Milky Way galaxy
• Gamma-ray astronomy – Observational astronomy performed with gamma rays
• List of unsolved problems in astronomy