Produced by the decay of radioactive elements, these particles rarely, if ever, interact with matter, making them extremely hard to detect and study. (ibtimes.com)
To detect very small quantities of mobile radioactive elements in the groundwater at former nuclear weapons production sites, researchers have developed a new type of sensor. (pnnl.gov)
This is light of extremely short wavelengths typically produced either among the stars / in cosmic rays or by radioactive element decay. (healthtap.com)