Which of the following accurately identifies a characteristic of positronium?

Positronium is a unique and short-lived atomic-like structure that forms when a positron (the antimatter counterpart of the electron) encounters an electron. This system is bound together by their mutual electromagnetic attraction. The statement that it forms briefly before annihilation is accurate because positronium typically has a very short lifespan—ranging from about 125 picoseconds to 142 nanoseconds—before it ultimately annihilates. During this annihilation process, the positron and electron collide and convert into energy, typically resulting in the emission of gamma rays.

The nature of positronium is such that it is inherently unstable and does not persist for long periods. This brief existence before annihilation is a fundamental characteristic that plays a key role in its detection and the application of positron emission tomography (PET) in medical imaging. In PET imaging, the detection of the annihilation photons emitted from the decay of positronium can be utilized to visualize metabolic processes in tissues.