Related by context. Frequent words. (Click for all words.) 69 cosmic microwave background 60 redshift 59 Spitzer Space Telescope 59 cosmologists 59 distant galaxies 59 NASA Chandra 58 astronomers 58 quasars 58 Planck 57 X ray Observatory 56 galaxy clusters 56 astrophysicists 56 galaxies 56 gamma ray bursts 56 THEMIS 55 spectroscopic 55 Space Telescope 55 supernovae 55 gamma ray burst 55 quasar 54 cosmological 54 exoplanets 54 exoplanet 54 Chandra X ray 54 NASA Cassini spacecraft 53 brown dwarfs 53 Cassini 53 general relativity 52 spectra 52 Einstein theory 52 cosmic ray 52 extrasolar planets 52 gravitational waves 51 Saturn rings 51 Mars Reconnaissance Orbiter 51 Raman spectroscopy 51 Big Bang theory 51 planets orbiting 51 pulsars 51 infrared wavelengths 50 supernovas 50 planets 50 Iapetus 50 spectroscopy 50 adaptive optics 49 supernova 49 JWST 49 pulsar 49 Astrophysical Journal 49 brown dwarf 49 neutrinos 49 telescope 49 neutrino 48 NASA Goddard 48 isotopic 48 astronomer 48 Astronomers 48 Kepler 48 quantum mechanics 48 Astrophysical Journal Letters 48 Hubble Space Telescope 48 Huygens 48 Big Bang 48 neutron stars 48 spectrometer 47 planet orbiting 47 Milky Way 47 Enceladus 47 celestial objects 47 Lunar Reconnaissance Orbiter 47 celestial bodies 47 LRO 47 rocky planets 47 Cassini spacecraft 47 neutron star 47 Milky Way galaxy 47 MESSENGER 47 dwarf galaxies 47 SDSS 47 cosmic 46 cosmic rays 46 Astrophysics 46 Hubble 46 spectrograph 46 astrophysicist 46 diffraction 46 physicists 46 HiRISE 46 infrared radiation 46 quantum theory 46 Very Large Telescope 46 astrophysics 46 gamma ray 46 NASA Hubble Space 45 Solar System 45 radioactive decay 45 RHIC 45 cosmology 45 magnetosphere 45 Saturn moon 45 nebula