Related by context. Frequent words. (Click for all words.) 49 XMM Newton 47 X ray Observatory 46 gamma ray bursts 46 gamma rays 45 NASA Chandra 45 Solar Dynamics 45 quasars 45 X ray emission 44 solar flares 44 infrared telescope 44 substorms 43 WM Keck Observatory 43 Kilauea volcano 43 gamma ray burst 43 observatories 43 astronomers 43 distant galaxy 43 Palomar Observatory 43 telescopes 42 GRBs 42 distant galaxies 42 COROT 42 aurora borealis 42 starlight 42 optical telescopes 42 celestial object 41 galaxy clusters 41 auroras 41 orbiting telescope 41 aurora 41 comet nucleus 41 observatory 41 ESO Very Large Telescope 41 Observatory 41 meteoroids 41 supernova 41 Saturn rings 41 Very Large Telescope 40 Perseids 40 occultation 40 quasar 40 galaxies 40 gravitational lensing 40 cosmic ray 40 Mars Reconnaissance Orbiter 40 Perseid meteor shower 40 celestial objects 40 CloudSat 40 meteor shower 40 cosmic microwave background 40 redshift 40 telescope 40 auroral 39 spiral galaxy 39 supernovas 39 comets 39 Orion Nebula 39 astrophysicists 39 astronomical objects 39 Gamma Ray 39 optical telescope 39 Andromeda Galaxy 39 supernova remnant 39 Hinode 39 supernovae 39 Hubble Space Telescope 39 Thirty Meter Telescope 39 gravitational wave 38 starbursts 38 Space Telescope 38 infrared wavelengths 38 Envisat 38 Geminids 38 galaxy cluster 38 orbiting observatory 38 LCROSS 38 Cassini 38 Eta Carinae 38 NASA Aqua 38 dwarf galaxies 38 Leonids 37 celestial bodies 37 field Infrared Survey 37 orbiting spacecraft 37 comet 37 THEMIS 37 infrared radiation 37 Cassini Huygens 37 spectroscopic 37 astrophysical 37 spacecraft 37 Telescope 37 astronomical observatory 36 meteors 36 polar regions 36 extrasolar planet 36 GRB 36 GLAST 36 extrasolar planets 36 astronomical observations 36 ionosphere