The STIS spectrograph viewed the entire inner ring in far-ultraviolet light, spreading it into a spectrum. The Earth's atmosphere completely blocks ultraviolet radiation from reaching the Earth's surface, hence astronomers can study the ultraviolet universe only from orbiting telescopes. The dark square in this image is where the spectrum was processed to remove the emission from hydrogen in the Earth's outer atmosphere.

Credit: George Sonneborn (Goddard Space Flight Center), Jason Pun (NOAO), the STIS Instrument Definition Team, and NASA/ESA