Credit: NASA/SDO and the AIA, EVE, and HMI science teams
This ultraviolet image of the Sun reveals a pair of coronal holes. Coronal holes are cooler and denser regions of the Sun's corona, it's outer atmosphere. Magnetic field lines in coronal holes do NOT loop back down to the Sun, so plasma flowing upward through the corona can more easily escape into space through these holes. The solar wind flows away from the Sun at higher speeds through coronal holes. This ultraviolet view of the Sun was captured by NASA's Solar Dynamics Observatory (SDO) spacecraft on January 12, 2011.