The Sun emitted a significant solar flare, peaking at 7:49 p.m. EST on February 24, 2014. NASA's Solar Dynamics Observatory, which keeps a constant watch on the Sun, captured images of the event.
Solar flares are powerful bursts of radiation, appearing as giant flashes of light in the SDO images. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel.
This flare is classified as an X4.9-class flare. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc.
Image Credit: SDO/NASA
Explanation from: http://www.nasa.gov/content/goddard/nasas-sdo-shows-images-of-significant-solar-flare/index.html