
Weaklings. Without penumbrae, which can be seen in the yellow image, today's sunspots are weakening magnetically.
Sunspots appear when upwellings of the sun's magnetic field trap ionized plasma - or electrically charged, superheated gas - on the surface. Normally, the gas would release its heat and sink back below the surface, but the magnetic field inhibits this process. From Earth, the relatively cool surface gas looks like a dark blemish on the sun.
Astronomers have been observing and counting sunspots since Galileo began the practice in the early 17th century. From those studies, scientists have long known that the sun goes through an 11-year cycle, in which the number of sunspots spikes during a period called the solar maximum and drops - sometimes to zero - during a time of inactivity called the solar minimum.