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Explanation: How do sunspots evolve? Large dark sunspots -- and the active regions that contain them -- may last for weeks, but all during that time they are constantly changing. Such variations were particularly apparent a few weeks ago as the active region AR 2339 came around the limb of the Sun and was tracked for the next 12 days by NASA's Solar Dynamic Observatory. In the featured time lapse video, some sunspots drift apart, while others merge. All the while, the dark central umbral regions shift internally and their surrounding lighter penumbras shimmer and wave. The surrounding Sun appears...

The sun produced its biggest solar flare so far this year, a huge blast that caused temporary radio blackouts throughout the Pacific. The X-class solar flare - considered the most powerful category of sun storm - erupted Tuesday from a sunspot called Active Region 2339 (AR2339), peaking at 6:11 p.m. EDT (2211 GMT), according to Space.com. The blast, however, is unlikely to cause major problems back on Earth. "Given the impulsive nature of this event, as well as the source location on the eastern limb of the sun, we are not expecting a radiation storm at Earth," scientists with the...