EUVE Sky Map . ... Credit Copyright: EUVE Project, NASA Explanation: The stars beyond the Sun and the distant galaxies should be undetectable at extreme ultraviolet wavelengths . At least that was the conventional wisdom when it was first realized that the space between the stars is filled with hydrogen , a strong absorber of extreme ultraviolet light. ... EUVE's scanning by orbit gives the picture a striped look while other instrument artifacts are seen as crosses and data gaps are dark. ...