Theta Aurora (IMAGE) NASA/Goddard Space Flight Center Caption A theta aurora -- so named because it looks like a Greek letter theta, a circle with a line through the middle -- as seen by NASA's IMAGE satellite on Sept. 15, 2005. New research helps explains what causes these unique events. Credit NASA/R. Fear et al (2014) Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.