Active region 10486 was the largest sunspot seen by the Solar & Heliospheric Observatory (SOHO). It unleashed a spectacular show on October 28, 2003.
An X 17.2 flare, the second largest flare observed by SOHO and the third largest ever recorded, blasted off a strong high-energy proton event and a fast-moving coronal mass ejection. The spot occupied an area equal to about 15 Earths, a size not seen since 1989.
It later fired off the largest X-ray flare recorded, on November 4, 2003.