positronium

Positronium is an exotic atom-like system made when a particle called a positron (the antimatter counterpart of an electron) meets an electron. Instead of forming a stable atom like hydrogen, they briefly pair up in a bound state before annihilating each other, releasing energy as gamma rays. This fleeting existence helps scientists study fundamental particle properties and antimatter behavior. Positronium has unique characteristics, such as a very short lifespan, and its behavior offers insights into quantum mechanics and the symmetry between matter and antimatter.