Changing Sun

Bright magnetic storms and geysers of hot gas highlight this image of the Sun at ultraviolet wavelengths by Solar Dynamics Observatory, a space telescope. The Sun's magnetic field varies with a roughly 11-year cycle, slightly changing its total energy output. Astronomer Charles Greeley Abbot, eventual secretary of the Smithsonian Institution, spent most of his career trying to quantify the Sun's total energy output as a tool for improving weather forecasts. [NASA/SDO (AIA)]