Final answer:
Sunspots are cooler due to increased magnetic activity, which disrupts convection, leading to cooled and denser gas that continues a self-perpetuating cycle.
Step-by-step explanation:
Sunspots remain cooler than their surroundings primarily because of the increased magnetic activity in these regions. The strong magnetic fields associated with sunspots interfere with the process of convection, which is normally responsible for bringing hot gas up from the interior of the Sun to its surface. This disruption creates a kind of 'plug' that prevents hot material from rising up into the sunspot region, leading to a cooler and darker appearance. Materials move around under a sunspot; cool material from the spot flows downward, while material surrounding the sunspot is pulled inward, creating a cycle that can sustain the sunspot for several weeks. Additionally, the gas in sunspots is cooler and denser, causing it to sink and reinforcing the cycle.