The sun’s 11-year magnetic cycle is winding down, so there shouldn’t be many sunspots on the star’s surface. Scientists were therefore surprised to see a new sunspot pop up, and even more surprised at its size. The dark blemish may seem tiny on the massive sun, but its core is larger than Earth.
Sunspots are areas of the solar surface with intense magnetic fields, and they’re dark because they are relatively cooler than their surroundings (by about 2,000 Kelvin). They are a common phenomenon, and through scientists aren’t entirely sure what causes them, they know that they’re more frequent when the sun produces its most magnetic activity, known as the solar maximum. At that time, which occurs on that 11-year cycle, the sun’s magnetic field flips, resulting in increased sunspots and solar flares. Here on Earth it makes for more intense auroras.
The sun is currently heading into a solar minimum, and its surface had been spot-free for two days before this new sunspot came into view. NASA’s Sun Dynamics Observatory satellite caught the first glimpse on July 5 and watched it grow until July 11. It’s by no means among the largest sunspots ever observed (those happen during maxima), but it’s certainly impressive for what should be a quiet time on the sun.