Size of a typical granule around 500-1000 km. THE SUN Sunspots are dark regions on the photosphere. Consist of darker center, called umbra , lighter outer region called penumbra which often shows spiky lines radiating outward like iron filings scattered around a magnet.
Spots range in size from a few thousand to many tens of thousands of km in diameter.
Often occur in pairs and groups. Darker center of sunspot is because of lower temperature, about 1500K lower than average for the photosphere. Looking at spectrum of sunspots, photospheric absorption lines appear split into pairs and multiples, evidence of the Zeeman effect , in which a strong magnetic field causes spectral lines to split. They look like eruptions, but time-lapse pictures show material moving downward even more often than upward. Their material is actually cooler than the surrounding corona.