Phil Plait at Slate has compiled a best-of list of astronomy images from 2012 that are pretty spectacular. Included is this image of the sun, which depicts an event that occurred on August 31, 2012. An arch of matter was raised by the sun's magnetic field and then erupted, sending hundreds of millions of tons of plasma into space at a speed of 900 miles per second. The size of the arch was 200,000 miles wide; 25 times the size of the Earth.
See the rest of the images at Bad Astronomy. Link
(Photo credit: NASA/GSFC/SDO)