Space matters that make their way to the Earth from other parts of the galaxy outside of the solar system. The solar system inside the Milky Way is surrounded by the heliosphere which is the boundary of solar wind, the stream of charged particles that's constantly blowing out from the Sun in all directions. The heliosphere shields the inner solar system from deadly cosmic radiation by using its magnetic field to push away damaging charged particles. These particles, or remnants from supernovae that are dispersed through interstellar space, flow toward the solar system at 50,000 miles (80,000 kilometers) an hour. But half of the particles in the interstellar wind are neutral, and these uncharged atoms can make it into our solar system.

In January 2012, a NASA spacecraft has for the first time directly observed alien particles that came from beyond our solar system. Orbiting the Earth at some 200,000 miles (322,000 kilometers) away, the Interstellar Boundary Explorer (IBEX) spacecraft was able to snag samples of hydrogen, oxygen, and neon that came from interstellar space.