20thcentury 520 astronomicalinstruments astronomy astrophysics congresses exploration extrasolarplanets gammarayastronomy history historyhubblespacetelescope(spacecraft) hubblespacetelescope(spacecraft) infraredtelescopes instruments largeastronomicaltelescopes lowtemperatureresearch nature nuclearastrophysics outerspace research skyobservation spaceastronomy spaceoptics spacetelescopes technologicalinnovations telescopes ultravioletastronomy unitedstates x-rayastronomy