Ultraviolet astronomy provide essential information about the evolution of galaxies. The ultraviolet universe looks quite different from the familiar stars and galaxies seen in visible light. Most stars are actually relatively cool objects emitting much of their electromagnetic radiation in the visible or near-infrared part of the spectrum. Ultraviolet radiation is the signature of hotter objects, typically in the early and late stages of their evolution. In the Earth's sky seen in ultraviolet light, most stars would fade in prominence. Some very young massive stars and some very old stars and galaxies, growing hotter and producing higher-energy radiation near their birth or
Ultraviolet (Light My Way) dealt with themes of anxiety and despair. Bono has described "Ultraviolet" as "an epic U2 song [but] the key of it left my voice in a conversational place and allowed a different kind of lyric writing." Producer Eno wrote that a combination of opposites within each song was a signature characteristic of "Achtung Baby" and that as part of that, "Ultraviolet" had a "helicopterish melancholy". In "Achtung Baby"s album package, "Ultraviolet" is presented next to a photograph of a crumbling Berlin building that has a Trabant parked in front of it. "Rolling Stone" noted that "Ultraviolet" was one of the