Solar Minimum versus Solar Maximum | NASA's Solar Dynamics Observatory FriendsofNASA.org: Our Sun is a 4.5 billion-year-old yellow dwarf star—a hot glowing ball of hydrogen and helium—at the center of our solar system. It is about 93 million miles (150 million kilometers) from Earth and our solar system’s only star. The height of the Sun’s activity cycle, known as solar maximum, is a time of greatly increased solar storm activity. Sunspots, eruptions called solar flares, and coronal mass ejectio