Related by context. Frequent words. (Click for all words.) 71 quasars 70 distant galaxies 68 galaxy cluster 67 galaxies 65 distant galaxy 65 XMM Newton 65 HD #b [002] 65 galaxy clusters 65 elliptical galaxies 64 quasar 64 globular clusters 64 GRBs 64 redshift 64 pulsars 63 spiral galaxies 63 astronomers 63 extrasolar planets 62 optical telescopes 62 infrared wavelengths 62 exoplanets 62 dwarf galaxies 61 spectroscopic 61 gravitational waves 61 brown dwarfs 60 gamma ray bursts 60 supernovae 60 planets 60 X ray Observatory 60 rocky planets 59 exoplanet 59 extrasolar planet 59 neutron stars 59 supernovas 58 cosmic microwave background 58 gamma rays 58 WM Keck Observatory 58 brown dwarf 58 gamma ray burst 58 planets orbiting 58 gravitational lensing 58 WMAP 58 astrophysicists 57 NASA Chandra 57 gamma ray 57 NASA Cassini spacecraft 57 Spitzer Space Telescope 57 cosmic rays 57 Milky Way Galaxy 57 Astronomers 57 Saturn rings 57 Milky Way 57 celestial objects 56 interstellar dust 56 neutrinos 56 wavelengths 56 Milky Way galaxy 56 terrestrial planets 56 galaxy 56 photons 56 neutron star 56 Saturn moons 56 cosmologists 56 supermassive black holes 56 neutrino 56 magnetic fields 55 comets 55 planet orbiting 55 nebulae 55 Einstein theory 55 Very Large Telescope 55 supernova 55 positrons 55 SDSS 55 nebula 54 spiral galaxy 54 ejecta 54 starlight 54 astrophysical 54 Solar System 54 pulsar 54 spectroscopy 54 spectra 54 subatomic particles 54 moons 54 comet 54 telescopes 54 Enceladus 53 celestial bodies 53 supermassive black hole 53 cosmic ray 53 supernova explosion 53 spectrometer 53 outer planets 53 infrared radiation 53 atoms 53 interstellar medium 53 nuclei 53 hydrogen atoms 53 spacetime 53 auroras 52 ringed planet