Final answer:
The less dark, outer region of a sunspot surrounding the dark central area, the umbra, is called the penumbra. Sunspots are cooler regions on the sun that appear darker; the largest can dwarf Earth in size.
Step-by-step explanation:
The outer region of a sunspot, surrounding the umbra, which is not as dark and not as cool as the central region is known as the penumbra. Sunspots are cooler areas on the Sun's surface, appearing darker than the surrounding areas. The umbra is the dark central part, while the penumbra is the lighter outer part. When observing sunspots, like the one captured in July 2012, they can be seen consisting of a central umbra and a surrounding penumbra. The largest sunspots can even be multiple times the size of Earth, and despite their dark appearance, they would be quite bright if observed against a night sky, roughly as bright as the full moon.
These solar phenomena can last anywhere from a few hours to a few months and often form in groups. The dynamics of sunspots are similar to the behavior of storms on Earth, drifting in position but at a slower pace compared to the Sun's rotation.