1925- 523 accretion(astrophysics) astronomicalinstruments astronomy astrophysics blackholes(astronomy) clusters compactobjects(astronomy) conferenceproceedings conferences congresses cosmicrays designandconstruction exosat(artificialsatellite) galactic galaxies gammarayastronomy gammaraybursts gammaraytelescopes highenergytransientexplorer(spacecraft) infraredastronomy instruments lowtemperatureresearch neutronstars nuclearastrophysics orbitingastronomicalobservatories particles(nuclearphysics) physics polarimetry pulsars sci004000 science scientificsatellites spaceastronomy spaceoptics sreekantan stars technologicalinnovations textbooks ultravioletastronomy ultravioletdetectors unitedstatesx-rayastronomyuseofartificialsatellites:einsteinobservatory x-rayoptics x-raysources x-raytelescopes xmmobservatory xrayastronomy