The Sun already featured one good-sized coronal hole, when another larger coronal hole began to emerge and intensify (Sept. 4-6, 2018). Coronal holes appear dark in extreme ultraviolet light, as is shown here. They are magnetically open areas from which solar wind streams out into space, and can last from days to months. The brighter area between the two coronal holes is an active region where the level of magnetic activity is strong.
SDO is managed by NASA's Goddard Space Flight Center, Greenbelt, Maryland, for NASA's Science Mission Directorate, Washington. Its Atmosphere Imaging Assembly was built by the Lockheed Martin Solar Astrophysics Laboratory (LMSAL), Palo Alto, California.