A 'Positron Excess' in cosmic emissions from deep space have recently been logged by various observation satellites ( PAMELA, Fermi-LAT and AMS-02 ).
As yet, there is no agreed explanation for the source of the positrons (i.e. 'anti' electrons ) in the numbers in which they are found.
There are (at least ) three current theories - some of which are contradictory. See: [all papers are from arXiv 2017]
Also see: Cosmic rays