Sunspots are the little black spots that occasionally show up on the Sun, but are they really black?

Sunspots are regions on the Sun's surface that are cooler. The temperature of the Sun's surface is around 5,500 degrees Celsius while that of sunspots are about 1,000 to 1,500 degrees lower than the surroundings. Since sunspots are cooler than the surroundings and give off less light, they appear dimmer than the rest of the Sun. These dimmer regions look "black" when we observe the Sun with equipment that reduce the intensity of sunlight by tens of thousands of times.

From the close-up image of the sunspots, we can see that they usually consist of central darker regions known as "umbra", surrounded by a less-dark region called "penumbra". Although sunspots are just little spots on the Sun, their actual size is usually larger than our Earth.

So, are sunspots really black? Not really!

(Photo taken by the Hong Kong Space Museum on 23 April, 2022. ⚠️⚠️Always use a camera equipped with safe sunlight filtering system for photographing the Sun. Do not look at the Sun directly.⚠️⚠️)