An asymmetric distribution of positrons in the Galactic disk revealed by γ-rays

@article{Weidenspointner2008AnAD,
  title={An asymmetric distribution of positrons in the Galactic disk revealed by $\gamma$-rays},
  author={Georg Weidenspointner and Gerald K. Skinner and Pierre Jean and J{\"u}rgen Kn{\"o}dlseder and Peter von Ballmoos and Giovanni Fabrizio Bignami and Roland Diehl and A. W. Strong and Bertrand Cordier and Stéphane Schanne and C. Winkler},
  journal={Nature},
  year={2008},
  volume={451},
  pages={159-162}
}
Gamma-ray line radiation at 511 keV is the signature of electron–positron annihilation. Such radiation has been known for 30 years to come from the general direction of the Galactic Centre, but the origin of the positrons has remained a mystery. Stellar nucleosynthesis, accreting compact objects, and even the annihilation of exotic dark-matter particles have all been suggested. Here we report a distinct asymmetry in the 511-keV line emission coming from the inner Galactic disk (∼10–50° from the… 

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