Sunspots on the surface of the Sun happen when magnetic fields rearrange and realign, forming dark spots Over the course of the last 48 hours, scientists watched a giant sunspot form - it has grown to over six Earth diameters across but its full extent is hard to judge since the spot lies on a sphere, not a flat disk.

The spot quickly evolved into what's called a delta region, in which the lighter areas around the sunspot, the penumbra, exhibit magnetic fields that point in the opposite direction of those fields in the center, dark area. This is a fairly unstable configuration that scientists know can lead to eruptions of radiation on the sun called solar flares.

 The bottom two black spots in the picture appeared quickly during Feb. 19th and 20th, 2013. These two sunspots are part of the same system and are over six Earths across. The image combines images from two instruments on NASA's Solar Dynamics Observatory (SDO): the Helioseismic and Magnetic Imager, which takes pictures in visible light that show sunspots and the Advanced Imaging Assembly, which took an image in the 304 Angstrom wavelength showing the lower atmosphere of the sun, which is colorized in red. 

 Credit: NASA/SDO/AIA/HMI/Goddard Space Flight Center