The Smallest Window on the Sun

Every so often, the Sun hurls billions of tonnes of charged particles toward Earth in what are called coronal mass ejections and if a big one hits at the wrong moment, the consequences for satellites, power grids, and communications systems could be catastrophic. Our best defence is to predict them before they happen, and that means watching the Sun's magnetic fields constantly and precisely. Now, a component smaller than a shirt button could transform how we do exactly that.