If the newly proposed low-mass dark matter particles are responsible for the unusual hydrogen ionization in the CMZ, they could also be generating the positrons that lead to the 511-keV emission line.

The release of energy during solar flares heats the chromosphere, causing almost full ionization of the atomic hydrogen present in the region.

The implications The higher degree of ionization found experimentally changes predictions of the compressibility, energy transport and opacity of matter deep inside planets and stars.

Previous studies suggested that cosmic rays—high-energy particles moving fast through space—could explain the hydrogen ionization. But there were problems with this theory.