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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 by the Fermi Gamma-ray Space Telescope and is unexplained by direct observation. Two percent of the gamma ray radiation in a 30° radius circle around the Galactic Center is attributed to the GCE. As of 2020, this excessive (and diffused) gamma-ray radiation is not well understood by astronomers.

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.

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, wavelet methods, and studies by other astronomers may support this idea. More recently, in August 2020, other astronomers have reported that self-annihilating dark matter may not be the explanation for the GCE after all. Other hypotheses include ties to a yet unseen population of millisecond pulsars or young pulsars, burst events, the stellar population of the galactic bulge, or the Milky Way's central supermassive black hole.

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

References

1. Goodenough, Lisa; Hooper, Dan (11 November 2009). "Possible Evidence For Dark Matter Annihilation In The Inner Milky Way From The Fermi Gamma Ray Space Telescope". arXiv:0910.2998 .
2. Wolchover, Natalie (3 March 2014). "Case for Dark Matter Signal Strengthens". Quanta Magazine. Retrieved 12 August 2021.
3. ^ Cho, Adrian (12 November 2019). "Physicists revive hunt for dark matter in the heart of the Milky Way". Science | AAAS. Retrieved 31 March 2020.
4. Starr, Michelle (30 April 2019). "Something's Glowing at The Heart of Our Galaxy, But It May Not Be What We Thought". ScienceAlert.com. Retrieved 30 April 2019.
5. ^ Leane, Rebecca K. & Slatyer, Tracy R. (17 April 2019). "Dark Matter Strikes Back at the Galactic Center". Phys. Rev. Lett. 123 (24): 241101. arXiv:1904.08430. doi:10.1103/PhysRevLett.123.241101. PMID 31922851. S2CID 210150636.
6. Fadelli, Ingrid (14 July 2020). "Could recently spotted dim point sources explain the galactic center excess (GCE)?". Phys.org. Retrieved 14 July 2020.
7. ^ Zhong, Yi-Ming; McDermott, Samuel D.; Cholis, Ilias & Fox, Patrick J. (2020). "Testing the Sensitivity of the Galactic Center Excess to the Point Source Mask". Phys. Rev. Lett. 124 (23): 231103. arXiv:1911.12369. Bibcode:2020PhRvL.124w1103Z. doi:10.1103/PhysRevLett.124.231103. PMID 32603155. S2CID 208512856.
8. "Is there dark matter at the center of the Milky Way?". MIT News. 10 December 2019. Retrieved 4 May 2023.
9. Cuoco, Alessandro; et al. (4 March 2019). "Scrutinizing the evidence for dark matter in cosmic-ray antiprotons". Physical Review D. 99 (10): 103014. arXiv:1903.01472. Bibcode:2019PhRvD..99j3014C. doi:10.1103/PhysRevD.99.103014. S2CID 119333152.
10. Cholis, Ilias; et al. (6 March 2019). "A Robust Excess in the Cosmic-Ray Antiproton Spectrum: Implications for Annihilating Dark Matter". Physical Review D. 99 (10): 103026. arXiv:1903.02549. Bibcode:2019PhRvD..99j3026C. doi:10.1103/PhysRevD.99.103026. S2CID 118857451.
11. Starr, Michelle (28 August 2020). "There's a Strange Glow in The Centre of Our Galaxy, And It's Not What We Thought It Was". ScienceAlert.com. Retrieved 28 August 2020.
12. Abazajian, Kevork N.; et al. (4 August 2020). "Strong constraints on thermal relic dark matter from Fermi-LAT observations of the Galactic Center". Physical Review D. 102 (43012): 043012. arXiv:2003.10416. Bibcode:2020PhRvD.102d3012A. doi:10.1103/PhysRevD.102.043012.
13. Bartels, Richard; et al. (February 2016). "Strong Support for the Millisecond Pulsar Origin of the Galactic Center GeV Excess". Physical Review Letters. 116 (5). 051102. arXiv:1506.05104. Bibcode:2016PhRvL.116e1102B. doi:10.1103/PhysRevLett.116.051102. PMID 26894696. S2CID 217518922.
14. Gautam, Anuj; Crocker, Roland M.; Ferrario, Lilia; Ruiter, Ashley J.; Ploeg, Harrison; Gordon, Chris; Macias, Oscar (28 April 2022). "Millisecond pulsars from accretion-induced collapse as the origin of the Galactic Centre gamma-ray excess signal". Nature Astronomy. 6 (6): 703–707. arXiv:2106.00222. Bibcode:2022NatAs...6..703G. doi:10.1038/s41550-022-01658-3. ISSN 2397-3366. S2CID 235265843.
15. Macias, Oscar; et al. (12 March 2018). "Galactic bulge preferred over dark matter for the Galactic centre gamma-ray excess". Nature Astronomy. 2 (5): 387–392. arXiv:1611.06644. Bibcode:2018NatAs...2..387M. doi:10.1038/s41550-018-0414-3. S2CID 54936254.
16. Hooper, Dan & Goodenough, Lisa (21 March 2011). "Dark matter annihilation in the Galactic Center as seen by the Fermi Gamma Ray Space Telescope". Physics Letters B. 697 (5): 412–428. arXiv:1010.2752. Bibcode:2011PhLB..697..412H. doi:10.1016/j.physletb.2011.02.029. S2CID 118446838.

Further reading

• Ackermann, M.; et al. (May 2017). "The Fermi Galactic Center GeV Excess and Implications for Dark Matter". The Astrophysical Journal. 840 (1). 43. arXiv:1704.03910. Bibcode:2017ApJ...840...43A. doi:10.3847/1538-4357/aa6cab. S2CID 119481146.
• Shang, Liangliang; et al. (May 2018). "Interpretations of galactic center gamma-ray excess confronting the PandaX-II constraints on dark matter-neutron spin-dependent scatterings in the NMSSM". European Physical Journal C. 78 (5). 390. arXiv:1804.08797. Bibcode:2018EPJC...78..390S. doi:10.1140/epjc/s10052-018-5827-8. S2CID 55864561.

v t e Black holes
Outline
Types	BTZ black hole Schwarzschild Rotating Charged Virtual Kugelblitz Supermassive Primordial Direct collapse Rogue Malament–Hogarth spacetime
Size	Micro Extremal Electron Stellar Microquasar Intermediate-mass Supermassive Active galactic nucleus Quasar LQG Blazar OVV
Formation	Stellar evolution Gravitational collapse Neutron star Related links Tolman–Oppenheimer–Volkoff limit White dwarf Related links Supernova Micronova Hypernova Related links Gamma-ray burst Binary black hole Quark star Supermassive star Quasi-star Supermassive dark star X-ray binary
Properties	Astrophysical jet Gravitational singularity Ring singularity Theorems Event horizon Photon sphere Innermost stable circular orbit Ergosphere Penrose process Blandford–Znajek process Accretion disk Hawking radiation Gravitational lens Microlens Bondi accretion M–sigma relation Quasi-periodic oscillation Thermodynamics Bekenstein bound Bousso's holographic bound Immirzi parameter Schwarzschild radius Spaghettification
Issues	Black hole complementarity Information paradox Cosmic censorship ER = EPR Final parsec problem Firewall (physics) Holographic principle No-hair theorem
Metrics	Schwarzschild (Derivation) Kerr Reissner–Nordström Kerr–Newman Hayward
Alternatives	Nonsingular black hole models Black star Dark star Dark-energy star Gravastar Magnetospheric eternally collapsing object Planck star Q star Fuzzball Geon
Analogs	Optical black hole Sonic black hole
Lists	Black holes Most massive Nearest Quasars Microquasars
Related	Outline of black holes Black Hole Initiative Black hole starship Black holes in fiction Big Bang Big Bounce Compact star Exotic star Quark star Preon star Gravitational waves Gamma-ray burst progenitors Gravity well Hypercompact stellar system Membrane paradigm Naked singularity Population III star Supermassive star Quasi-star Supermassive dark star Rossi X-ray Timing Explorer Superluminal motion Timeline of black hole physics White hole Wormhole Tidal disruption event Planet Nine
Notable	Cygnus X-1 XTE J1650-500 XTE J1118+480 A0620-00 Sagittarius A* Centaurus A Phoenix Cluster PKS 1302-102 OJ 287 SDSS J0849+1114 TON 618 MS 0735.6+7421 NeVe 1 Hercules A 3C 273 Q0906+6930 Markarian 501 ULAS J1342+0928 PSO J030947.49+271757.31 AT2018hyz Swift J1644+57
Category Commons

v t e Milky Way
Location	Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow (→) may be read as "within" or "part of".
Structure	Galactic Center Sagittarius A Sagittarius A* Fermi bubbles Supermassive black hole Galactic Center filaments Disk Carina–Sagittarius Norma–Cygnus Orion–Cygnus Perseus Scutum–Centaurus Near 3 kpc Arm Far 3 kpc Arm Halo Aquarius Stream Fimbulthul stream Gaia Sausage Helmi stream Magellanic Stream Monoceros Ring Palomar 5 stream Pisces-Eridanus stream Sagittarius Stream Virgo Stream
Satellite galaxies	Magellanic Clouds Large Magellanic Cloud Small Magellanic Cloud Magellanic Bridge Dwarfs Antlia II Boötes I Boötes II Boötes III Canes Venatici I Canes Venatici II Canis Major Carina Coma Berenices Crater 2 Draco Eridanus II Fornax Hercules Leo I Leo II Leo IV Leo V Leo T Phoenix Pisces Overdensity Pisces II Reticulum II Sagittarius Spheroidal Segue 1 Segue 2 Sculptor Sextans Triangulum II Ursa Major I Ursa Major II Ursa Major III Ursa Minor Virgo I Willman 1
Related	Alternate names Andromeda–Milky Way collision Baade's Window In mythology Zone of Avoidance
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