I had students out for a solar observing session on 10/29. One of the objects we observed was the giant sunspot AR 12192. Shown below are a couple photos I took of this region using our H-alpha filter which lets in only a narrow band of light associated with the H-alpha line in the hydrogen emission spectrum (656.28-nm). This suppresses the blinding glare from the surface and allows us to see details not only on the surface but in the solar atmosphere.
This sunspot is about 10-times the diameter of Earth and is the largest seen in 20-years! It looks flat because rotates once every 25-days and the spot has rotated around and is about to disappear from sight. The prominence seen is likely the aftermath of a solar flare that erupted on the surface near the spot a few hours before. Six major X-class flares have come from this spot and have intermittently disrupted navigation and radio communication.
Sunspots occur when strong magnetic fields protruding from the surface disrupt the convective up-flow of hot gas toward the surface. This creates a region on the surface where the temperature is lower than the surrounding surface. The instruments used to observe the spots have to reduced the glaring light coming from the rest of the surface making the spots appear dark. In fact, most of the solar activities near the surface (prominences, flares, coronal mass ejections, etc.) are also believed to be magnetically driven. The other photo is of a large prominence seen in a different area.
