As a soupy mix of electrons and ions that forms under certain conditions in the most extreme of environments, plasma is an inherently difficult thing to observe. Scientists have made a significant breakthrough in the way we study this phenomenon, managing to trap an ultracold form of it in a magnetic "bottle" for the first time, an achievement that could act as a springboard for research into nuclear fusion energy, and what we understand of the Sun and the stars.

Generally speaking, it takes extremely hot temperatures for plasma to form, like those found in the Sun or in a lightning strike. Scientists at Rice University have been exploring how a technique known as laser cooling, developed in the 1990s to slow atoms down almost to a halt, can be used to create low-temperature, low-density plasma and study how it behaves in the lab. In 2019, the team published a paper describing its method of creating laser-cooled plasma around 50 times colder than that found in space.

The plasma the scientists were working with in their latest experiments is described as the world's coldest, at around one degree above absolute zero, or -272 °C (457.6 °F). This ultracold plasma expands rapidly once it is created, dissipating entirely within just a few thousandths of a second. Using what's known as a quadrupole magnet setup, which is similar to the systems used to confine plasma in experimental fusion energy systems, the team was able to trap and hold its ultracold plasma in place for several hundredths of a second instead.