Related by context. Frequent words. (Click for all words.) 68 planets 65 galaxy 64 Milky Way galaxy 64 Milky Way 64 distant galaxies 63 comets 62 galaxies 62 Kuiper Belt 60 Saturn rings 60 asteroid belt 59 extrasolar planets 59 magnetosphere 58 comet 58 Universe 58 interstellar space 57 supernova 56 nebula 56 planetary 56 neutron stars 56 exoplanets 56 astronomers 56 Enceladus 56 moons 56 neutron star 55 exoplanet 55 celestial bodies 55 quasars 55 supernovae 55 asteroids 55 cosmos 55 Galaxies 54 Earth 54 Cassini 54 gamma ray burst 54 Astronomers 54 gamma ray bursts 54 orbits 53 solar flares 53 universe 53 Uranus 53 cosmic rays 53 Red Planet 53 pulsar 53 pulsars 53 Saturn moon 53 supermassive black holes 53 galaxy clusters 53 Mars 52 Martian surface 52 Spitzer Space Telescope 52 planet 51 Martian atmosphere 51 orbiting 51 brown dwarf 51 galactic 51 Sedna 51 Pluto 51 supermassive black hole 51 supernovas 51 asteroid 51 MESSENGER 50 ionosphere 50 quasar 50 infrared wavelengths 50 Planck 49 telescope 49 organic molecules 49 corona 49 Huygens 49 Astronomy 49 Earths 49 Earth orbit 49 Hubble 49 Planets 48 neutrinos 48 Spacecraft 48 Martian 48 martian 48 spacecraft 48 lunar surface 48 Telescope 48 magnetic fields 47 cosmic 47 gamma rays 47 Tempel 1 47 meteorites 47 Hubble telescope 47 atoms 47 LCROSS 47 Saturn 47 habitable zone 47 telescopes 46 Einstein theory 46 cosmological 46 Andromeda 46 starlight 46 Astrophysics 46 Cassini spacecraft 46 Pleiades 46 celestial 45 astrophysicists