X-CLASS FLARE On December 19, 2014, a powerful flare erupted on the Sun. This composite image from NASA's Solar Dynamics Observatory blends two wavelengths of extreme ultraviolet light, 17.1 nm (gold) and 13.1 nm (purple). Scientists rate flares according to their X-ray intensity; this flare (bright region, center right) they rated as X1.8, which puts it in the most intense category, X. The largest flare ever observed unleashed at least 15 times as much energy - fortunately, that one wasn't pointed at Earth. Sk yandTelescope.com November 2015 23