Cosmic rays

So-called "cosmic rays" are high-speed high-energy particles
which shoot throughout the universe in all directions.
Most of them are protons, and most of the rest are electrons,
but there are also anti-protons, alpha-particles (helium nuclei),
and heavier nuclei among them.

Most of the cosmic rays, including the protons, electrons, and antiprotons,
are created by massive quark-stars (which are commonly called "black holes"),
which emit high-energy gamma-rays, which then split-into high-speed
proton-antiproton pairs. Those antiprotons in-turn decay into electrons.
Thus, high-speed protons and high-speed electrons are produced.

There are menny gas-atoms in intergalactic space,
which those particles often collide with, and which change their direction,
but do not stop them.
Becuz of their high momentum, cosmic-ray particles can travel vast
intergalactic distances before they are stopped.