ESTEC cloud chamber reveals background radiation and cosmic rays

A close-up of the cloud chamber installed at ESTEC, employed to make ionising radiation visible to the naked eye. The tracks seen here are generated by actual background radiation particles, which ionise the alcohol vapour under the glass, creating condensation tracks with characteristic shapes. For instance, an alpha particle (a high energy helium nuclei) track is thick and straight, while a beta particle (an electron or positron) track is wispy and shows more evidence of deflections by collisions.

Particle radiation surrounds us in everyday life, coming from a variety of natural sources present in the ground, in food, in water and in the air, known as background radiation. Radiation also comes from space, known as Galactic Cosmic Rays. Despite their name they are particles that originate mainly from exploding supernovas which potentially occurred hundreds of thousands of years ago.