With the identification of the Higgs boson at CERN’s Large Hadron Collider, scientists put the last piece of the Standard Model of physics in place. What they haven’t found is any hint of something beyond the Standard Model. And that hasn’t been for lack of trying. Supersymmetry, the most popular extension to the Standard Model, predicts a large collection of additional particles. We’ve looked for them and, so far, they have not shown up.

But some extensions of the Standard Model don’t predict the sorts of heavy particles that the LHC is designed to identify. Instead, they suggest there’s a very light force-carrying particle called an axion. With the right properties, an axion could solve issues in everything from particle interactions up to the scale of galaxy clusters. But its tiny mass and odd behavior means it won’t be detected in the LHC.

But that doesn’t mean the LHC’s hardware can’t find it. Clever engineers at CERN took magnets originally designed for the LHC, combined them with X-ray focusing technology originally designed for space, and built a device that could spot axions arriving here from the Sun. So far, it has seen no sign of them, which places some strict limits on the properties of these hypothetical particles.