Now the sun has a circle. What happened?

This is a typical solar halo. Solar halo (solar halo; Solar flare) is a light phenomenon formed by the refraction of sunlight when it passes through ice crystals in clouds, and it is annular and colorful around the sun. The appearance of solar halo often indicates that the weather will change to some extent. Solar halo is a rare astronomical phenomenon, which can be divided into total halo and gap halo.

When the viewing angle corresponding to the solar halo radius is between 22 and 46, people can observe the phenomenon of "solar halo" with the naked eye. The greater the ice crystal content in the cloud, the smaller and more obvious the halo of "solar halo" after sunlight refraction, which is easy for people to observe; On the other hand, a "solar halo" cannot be formed, or even if it is formed, it cannot be clearly observed on the ground.