Say cheese!
According to experts, dark regions on the Sun are called coronal holes. These areas of low temperature and plasma density are explained as regions where a fast solar wind flows from the surface of the star into space. Their position resembling a smile in the photo is purely coincidental.
NASA’s Solar Dynamics Observatory photographs the Sun every 12 seconds at 10 different wavelengths of the ultraviolet spectrum. The data is then processed by Space Weather Prediction Center computers to determine the temperature, velocity and density of solar particles.