Two hours later, a magnetic filament near sunspot AR3089 became unstable and erupted at 14:00 UT (18:00 local time). This large sunspot has been disconcertingly quiet this week, leading some astronomers to worry that a big solar flare may be building. This sunspot has been mellow, but that doesn’t mean it’s going away. It has been observed that this sunspot has developed a delta-class magnetic field that harbors energy for X-class solar flares. That’s the strongest flare class, but there is quite a bit of variation within the X-class, which can produce as much energy as a billion hydrogen bombs on the most intense end of the scale.