Igniting a miniature sun is a long-held dream of humanity. Typically, scientists try to confine scorching plasma (a gas of charged particles) at temperatures of hundreds of millions of degrees. But plasma tends to escape magnetic traps, and confinement comes at enormous cost.

New research suggests a different path: instead of heating all the fuel, shoot a beam of fast particles at a target. The beam is like a billiard ball rolling through a crowd of people. The people are electrons in the target, slowing the ball and draining energy. If you remove the crowd, the ball reaches its goal, the nucleus, almost unimpeded. Similarly, if you strip the target of its electrons, you're left with 'naked' nuclei that barely hinder the beam. Then the beam particles fuse with the target nuclei, turning hydrogen into helium and releasing energy.

For comparison, in traditional approaches, plasma is heated to 150 million degrees — ten times hotter than the sun's core, because the density there is much lower. In the new method, temperature isn't crucial; precision is: a dense beam reaches the nucleus without interference. This could make fusion reactors simpler and cheaper, without complex magnetic systems. If the approach pans out, humanity will gain a nearly inexhaustible source of clean energy, leaving no radioactive waste.