Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. Sometimes, small regions of the Sun appear unusually dark. Visible above is a close-up picture of a sunspot , a depression on the Sun's face that is slightly cooler and less luminous than the rest of the Sun . The Sun's complex magnetic field creates this cool region by inhibiting hot material from entering the spot .
Sunspots can be larger than the Earth and typically last for only a few days.
This high-resolution picture also shows clearly that the Sun's face is a bubbling sea of separate cells of hot gas. These cells are known as granules . A solar granule is about 1000 kilometers across and lasts about 10 minutes. After that, many granules end up exploding. Specific rights apply .