Related by context. Frequent words. (Click for all words.) 65 planets 57 planet 55 exoplanets 55 Earth 54 planetary 54 galaxies 53 galaxy 53 galactic 52 moons 52 universe 52 extrasolar planets 50 Milky Way 50 distant galaxies 50 supernovae 50 supermassive black holes 49 cosmic 49 Milky Way galaxy 49 exoplanet 49 Solar System 49 comets 49 asteroid 48 Asteroids 48 antimatter 48 Saturn rings 48 asteroids 48 cosmos 48 comet 48 Galaxies 47 Saturn moon 47 celestial bodies 47 orbits 47 Enceladus 47 pulsars 47 neutron star 47 gamma ray bursts 47 brown dwarf 47 neutrinos 47 Planetary 47 interstellar 46 Sedna 46 quasars 46 oceans 45 Earthlings 45 intergalactic 45 Pluto 45 atoms 45 asteroid belt 45 supernova 45 solar flares 45 Uranus 45 Martian 45 neutron stars 44 habitable zone 44 universes 44 Planets 44 neutrons 44 suns 43 Red Planet 43 quasar 43 Universe 43 hydrogen atoms 43 organic molecules 42 Martian surface 42 Galactic 42 Astronomers 42 Kuiper Belt 42 mass extinction 42 habitable 42 nebula 42 Mars 42 Martian atmosphere 41 Cassini 41 gamma rays 41 cosmic rays 41 astrophysicists 41 astronomers 41 meteorites 41 Moons 41 meteors 41 Higgs boson 41 nuclei 41 helium 40 orbiting 40 martian 40 cosmological 40 Planck 40 interplanetary 40 interstellar space 40 Andromeda 40 biosphere 40 earthlings 40 subatomic particles 39 Spitzer Space Telescope 39 extraterrestrial 39 Asteroid 39 protons 39 quarks 39 Big Bang 39 Tempel 1 39 volcanic activity 39 aliens